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JP2016014581

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DESCRIPTION JP2016014581
An object of the present invention is to equalize the characteristics of a film portion on which a
sensor is mounted. A pressure sensor according to an embodiment described below includes a
support, a flexible film supported by the support, and a strain sensing element formed on the
film. . The strain sensing element includes a first magnetic layer formed in a film portion and
having magnetization, a second magnetic layer having magnetization, and an intermediate layer
formed between the first magnetic layer and the second magnetic layer. . The direction of at least
one of the magnetization of the first magnetic layer and the magnetization of the second
magnetic layer changes relative to the other according to the strain of the film portion. The film
portion includes an oxide layer containing aluminum. [Selected figure] Figure 1
Pressure sensor, microphone using pressure sensor, blood pressure sensor, and touch panel
[0001]
Embodiments described herein relate to a pressure sensor, and a microphone, a blood pressure
sensor, and a touch panel using the pressure sensor.
[0002]
In recent years, pressure sensors using spin technology have been proposed.
A pressure sensor using spin technology is a device that measures pressure using the principle
that the magnetization direction in a plurality of magnetic layers changes relatively as pressure
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changes, which changes the value of the electric resistance of the element. It is. In such a
pressure sensor, a strain sensing element using spin technology is disposed on the film section
formed on the support section, and the strain of the film section caused by pressure is converted
into resistance change of the strain sensing element. Thus, the pressure applied to the membrane
part is detected (Patent Document 1).
[0003]
In such a pressure sensor, a structure has been proposed in which strain sensing elements using
a plurality of spin techniques are disposed in one film portion that is bent by pressure (see, for
example, Patent Document 2). In a pressure sensor having a plurality of strain sensing elements,
it is desirable to exhibit a response that does not cause unintended characteristic variations
among the elements of each strain sensing element.
[0004]
In order to improve the performance of such a pressure sensor, it is preferable that the
characteristics of the film part including the film thickness of the film part be uniform. However,
in the pressure sensor using the material of the conventional film part, it is difficult to make the
characteristics of the film part uniform, and therefore, it has not been easy to improve the
performance of the pressure sensor.
[0005]
JP, 2002-22584, A JP, 2011-244938, A
[0006]
The pressure sensor according to the embodiment described below makes it possible to equalize
the characteristics of the film portion on which a plurality of strain sensing elements are
mounted.
[0007]
The pressure sensor according to the embodiment described below includes a support, a flexible
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film supported by the support, and a strain sensing element formed on the film.
The strain sensing element includes a first magnetic layer formed in a film portion and having
magnetization, a second magnetic layer having magnetization, and an intermediate layer formed
between the first magnetic layer and the second magnetic layer. .
The direction of at least one of the magnetization of the first magnetic layer and the
magnetization of the second magnetic layer changes relative to the other according to the strain
of the film portion. The film portion includes an oxide layer containing aluminum.
[0008]
It is a typical perspective view showing composition of a pressure sensor concerning a 1st
embodiment. It is a typical sectional view showing the composition of the pressure sensor. It is a
schematic plan view which shows the structure of the pressure sensor. It is a schematic plan view
which shows the structure of the pressure sensor. It is a schematic plan view which shows the
structure of the pressure sensor. It is a schematic plan view which shows the structure of the
pressure sensor. FIG. 6 is a schematic plan view showing the arrangement position of the strain
sensing element 200 on the film section 120. It is a typical perspective view showing
composition of a distortion sensing element concerning a 1st embodiment. FIG. 7 is a schematic
view for explaining the operation of the strain sensing element 200. It is a typical perspective
view showing the example of composition of the distortion sensing element. It is a typical
perspective view showing the example of composition of the distortion sensing element. It is a
typical perspective view showing other examples of composition of the distortion sensing
element. It is a typical perspective view showing other examples of composition of the distortion
sensing element. It is a typical perspective view showing other examples of composition of the
distortion sensing element. It is a typical perspective view showing other examples of
composition of the distortion sensing element. It is a typical perspective view showing other
examples of composition of the distortion sensing element. It is a typical sectional view showing
a problem in a process of processing hollow part 111 of pressure sensor 110A of a 1st
embodiment. It is a typical sectional view showing a problem in a process of processing hollow
part 111 of pressure sensor 110A of a 1st embodiment. It is a conceptual diagram explaining the
method of a deformation | transformation of the film part 120. FIG. The manufacturing process
in the case of forming the hollow part 111 by etching the board | substrate 110 is shown. It is a
table | surface which shows the selection ratio with respect to silicon. It is the schematic for
demonstrating the apparatus which evaluates the sensitivity with respect to the applied pressure
of the vibration part 121 of the film | membrane part 120, and its evaluation method. It is the
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schematic of the change of the shape of the film | membrane part 120 when the application
pressure 80 is added. It is the actual image data which shows the measurement result by the
laser microscope M3 in the initial state where the application pressure 80 from the outside is not
added when using sputtered aluminum oxide (AlOx) as a material of the film part 120. It is the
figure which showed height distribution of the orthogonal | vertical direction (Z-axis direction) of
the film | membrane part 120 shown by the image data of FIG. 17A with the contrast of a color.
The result of having measured the change of the shape in the B-B 'cross section of Drawing 17A
at the time of applying various applied pressure 80 to film part 120 with laser microscope M3 is
shown. In the case of FIG. 17C, the horizontal axis represents applied pressure 80, and the
vertical axis represents displacement D of the center of gravity 120P1 of the film portion 120. It
is an A-A 'cross section figure of Drawing 1 in a pressure sensor of a 2nd embodiment.
The film thickness h1, h2 and h3 of the first film 131, the intermediate film 132 and the second
film 133 constituting the film portion 120, and the residual stress σ1, σ2 and the first film 131,
the intermediate film 132 and the second film 133 It is the schematic which shows (sigma) 3. It
is the schematic explaining the reason which can suppress the bending which generate | occur |
produces in the film part 120 in the state to which the pressure from the outside is not added by
the film part 120 of 3 layer structure of 2nd Embodiment. The modification of 2nd Embodiment
is shown. External pressure application pressure in the case of using AlOx sputtered as the
material of the first film 131 and the second film 133 and using a SiNx film formed of CVD
(Chemical Vapor Deposition) as the material of the intermediate film 132 Is an actual image data
showing the measurement result by the laser microscope M3 in the initial state in which no is
added. It is the figure which showed height distribution of the orthogonal | vertical direction (Zaxis direction) of the film | membrane part 120 shown by the image data of FIG. 21B with the
contrast of a color. The change of the shape of the B-B 'cross section of FIG. 21B at the time of
applying various applied pressure to the film | membrane part 120 is shown with the result of
having measured with the laser microscope M3. 21D is a graph in which the horizontal axis
represents applied pressure 80 and the vertical axis represents displacement D of the center of
gravity 120P1 of the film part 120. It is an A-A 'cross section figure of Drawing 1 in a pressure
sensor of a 3rd embodiment. It is an A-A 'cross section figure of Drawing 1 in a pressure sensor
of a 4th embodiment. An example of a design of pressure sensor 110A concerning a 1st-4th
embodiment is shown. The other example of the design of pressure sensor 110A concerning the
1st-4th embodiment is shown. It is a schematic diagram of the cross-section of the pressure
sensor 110A at the time of using for the film | membrane part 120 as shown in 1st Embodiment.
It is a schematic diagram of the cross-section of the pressure sensor 110A at the time of using for
the film | membrane part 120 as shown in 2nd Embodiment. It is a typical sectional view
showing the composition of the microphone concerning a 5th embodiment. It is a schematic
diagram which shows the structure of the blood pressure sensor which concerns on 6th
Embodiment. It is a typical sectional view seen from H1-H2 of the blood pressure sensor. It is a
typical circuit diagram showing composition of a touch panel concerning a 7th embodiment.
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[0009]
Hereinafter, the pressure sensor according to the embodiment will be described with reference to
the drawings. The drawings are schematic or conceptual, and the relationship between the film
thickness and width of each portion, the ratio of sizes between portions, and the like are not
necessarily the same as the actual ones. In addition, even in the case of representing the same
portion, the dimensions and ratios may be different from one another depending on the
drawings. In the specification of the present application and the drawings, the same elements as
those described above with reference to the drawings are denoted by the same reference
numerals, and the detailed description will be appropriately omitted.
[0010]
First Embodiment First, a pressure sensor according to a first embodiment will be described with
reference to FIG. FIG. 1 is a schematic perspective view illustrating a pressure sensor 110A and a
strain sensing element 200 according to the first embodiment. Note that, in FIG. 1, only a part of
the strain sensing element 200 is shown to make the drawing easier to understand, and the
illustration of the insulating part is omitted, and the conductive part is mainly drawn.
[0011]
2 is a schematic cross-sectional view seen from A-A 'of FIG. FIG. 3 is a schematic plan view
showing the configuration of the pressure sensor 110A. Furthermore, FIG. 4 is a schematic
perspective view showing the configuration of the strain sensing element 200, and FIG. 5 is a
schematic cross-sectional view for explaining the operation of the pressure sensor 110A.
[0012]
As shown in FIG. 2, the pressure sensor 110 </ b> A includes a film unit 120 and a strain sensing
element 200 formed on the film unit 120. The membrane portion 120 has flexibility to be
generated and flexed in response to external pressure. The strain sensing element 200 is strained
according to the bending of the film portion 120, and changes the electrical resistance value
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according to the strain. Therefore, by detecting a change in the electrical resistance value of the
strain sensing element 200, an external pressure is detected. The pressure sensor 110A may
detect a sound wave or an ultrasonic wave. In this case, the pressure sensor 110A functions as a
microphone or an ultrasonic sensor.
[0013]
As shown in FIG. 1, the pressure sensor 110 </ b> A includes a substrate 110, a film unit 120
provided on one surface of the substrate 110, and a strain sensing element 200 provided on the
film unit 120. Further, on the film portion 120, a wire C1, a pad P1, a wire C2, and a pad P2
connected to the strain sensing element 200 are provided. Hereinafter, the direction
perpendicular to the substrate 110 is taken as the Z direction. Further, a predetermined direction
perpendicular to the Z direction is taken as an X direction, and a direction perpendicular to the Z
direction and the X direction is taken as a Y direction.
[0014]
As shown in FIG. 2, the substrate 110 is a plate-like substrate having a hollow portion 111, and
functions as a support portion for supporting the film portion 120 so that the film portion 120
bends in accordance with the external pressure. In the present embodiment, the hollow portion
111 is, for example, a cylindrical hole which penetrates the substrate 110 (as described later, it
may have another shape). The substrate 110 is made of, for example, a semiconductor material
such as silicon, a conductive material such as metal, or an insulating material. Further, the
substrate 110 may include, for example, silicon oxide (SiOx), silicon nitride (SiNx), or the like. On
the other hand, the film portion 120 is formed of an oxide containing aluminum, such as
aluminum oxide. The hollow portion 111 is formed by etching the substrate 110 to process the
substrate 110 until the film portion 120 is exposed.
[0015]
The inside of the hollow portion 111 is designed such that the film portion 120 can be bent, for
example, in a direction (Z-axis direction) perpendicular to the main plane of the substrate 110.
For example, the inside of the hollow portion 111 may be in a reduced pressure state or a
vacuum state. In addition, the interior of the hollow portion 111 may be filled with a gas or liquid
such as air or an inert gas. Furthermore, the hollow portion 111 may be in communication with
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the outside.
[0016]
As shown in FIG. 2, the film portion 120 is formed thinner than the substrate 110. Also, the film
unit 120 is positioned immediately above the hollow portion 111, and includes a vibrating
portion 121 that bends according to an external pressure, and a supported portion 122
integrally formed with the vibrating portion 121 and supported by the substrate 110. For
example, as shown in FIG. 3A, the supported portion 122 surrounds the vibrating portion 121.
Hereinafter, a region located immediately above the hollow portion 111 of the film portion 120
will be referred to as a first region R1. The vibrating portion 121 and the supported portion 122
are each formed of an oxide (for example, aluminum oxide) containing aluminum (Al). The total
thickness t1 of the film portion 120 can be, for example, 50 nanometers (nm) or more and 3
micrometers (μm) or less. In this case, preferably, the thickness can be 100 nm or more and 2
μm or less.
[0017]
The first region R1 can be formed in various shapes. For example, as shown in FIG. 3A, the first
region R1 may be formed in a substantially circular shape, or as shown in FIG. It may be formed
in a shape), may be formed in a substantially square shape as shown in FIG. 3C, or may be
formed in a rectangular shape as shown in FIG. 3D. The first region R1 can also be a polygon or a
regular polygon. Also, the first region R1 may be a combination of the above shapes. When the
first region R1 is a rectangle, a square, a polygon or the like, the corner may be sharp or the
corner may be rounded.
[0018]
As shown in the following embodiments, in the case of a strain sensing element using spin
technology, the shape of the film unit 120 is the XY anisotropy of the strain generated in the film
unit when pressure is applied to the film unit. It is preferable that the shape has a high degree of
elasticity, for example, a shape close to a rectangle. This makes it possible to arrange a large
number of strain detection elements by spin technology, and as a result, the signal-to-noise ratio
(SNR: Signal-to-Noise Ratio) according to the number N of elements is improved. Assuming that
individual strain sensing elements exhibit the same output, the SNR improvement effect when
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using a plurality of element numbers N is 20 log NN, and the larger the number of N, the better
the SNR. This is because when the strain sensing elements are connected in series, the signal
increases in proportion to the number N of elements by N times, while the noise is proportional
to √N according to the number N of elements. As it increases, the SNR is attributable to
improvement by the effect of 20 log (N / NN) = 20 log NN.
[0019]
In addition, when the planar shape of 1st area | region R1 is a perfect circle shape, the diameter
dimension of 1st area | region R1 can be 1 micrometer or more and 1000 micrometers or less,
for example. In this case, preferably, it can be 60 μm or more and 600 μm or less.
[0020]
When the planar shape of the first region R1 is a square, the length of one side of the first region
R1 can be, for example, 1 μm or more and 650 μm or less. In this case, preferably, it can be 50
μm or more and 550 μm or less. When the planar shape of the first region R1 is rectangular,
the length of the short side of the first region R1 can be, for example, 1 μm or more and 500
μm or less. In this case, preferably, it can be 50 μm or more and 400 μm or less.
[0021]
FIG. 3E is a schematic plan view showing the arrangement position of the strain sensing element
200 on the film portion 120. As shown in FIG. As an example, a rounded rectangle is adopted at
the corner in the shape of the first region R1. The reason why the corners of the shape of the
first region R1 are rounded in this way is that when the film portion is etched by RIE (Reactive
Ion Etching) or the like, the etching rate differs between the corners and the central portion. This
is performed to suppress the adverse effect of the film thickness distribution of the portion 120.
The roundness R of the corner in this case depends on the area of the film portion 120, but it is a
desirable design that R = 30 to 100 μm. In order to perform etching uniformly while keeping the
XY anisotropic strain large, it is preferable to set R = about 70 μm.
[0022]
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The strain sensing element 200 is preferably disposed at the end of the first region R1. Here,
“the end of the first region R1” is a point 120P6 on the boundary between the supported
portion 122 and the vibrating portion 121 and the center of gravity 120P1 of the first region R1
and the point 120P6 as shown in FIG. 3E. The position between the connecting line and the
midpoint 120P7 is shown. This is because distortion of the vibrating portion 121 is easily
generated at the end of the first region R1, and the detection sensitivity of the distortion is
enhanced. Further, since the strain sensing element 200 senses strain by rotation of
magnetization in the magnetic layer, the direction of the strain is better when the strain sensing
element 200 is located at the end of the first region R1. It is because it is easy to distinguish.
However, as shown in FIGS. 3B and 3D, in the case of the first region R1 having different
dimensions in the vertical direction and the horizontal direction as in FIG. 3B (elliptical shape)
and FIG. 3D (rectangle) Instead of arranging the strain sensing element 200 at the end of R1, it
may be arranged near the center of the first region R1.
[0023]
Further, as shown in FIG. 3E, when the first region R1 of the film portion 120 is projected onto a
plane (for example, an XY plane) parallel to the first region R1, the points 120P2, 120P3, 120P4
and 120P5 are obtained. In the enclosed area, the minimum circumscribed rectangle 120S of the
area R1 can be formed. The minimum circumscribed rectangle 120S is a region 120S1 formed by
connecting points 120P2, 120P3 and the center of gravity 120P1 by line segments, a region
120S2 formed by connecting the points 120P4 and 120P5 and the center of gravity 120P1 by
line segments, and a point 120P3. A region 120S3 is formed by connecting points 120P4 and
centers of gravity 120P1 by line segments, and a region 120S4 is formed by connecting points
120P2, 120P5 and centers of gravity 120P1 by line segments.
[0024]
Further, as shown in FIG. 3E, a plurality of strain sensing elements 120 are disposed on a region
of the film portion 120 where the first region R1 and the region 120S1 overlap. Further, at least
two of the plurality of strain sensing elements 200 disposed on the overlapping region of the
first region R1 and the region 120S1 have a position in a direction parallel to the line segment
120S11 connecting the point 120P2 and the point 120P3. Different from each other.
[0025]
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Next, a schematic configuration of the strain sensing element 200 according to the present
embodiment will be described with reference to FIG. FIG. 4 is a schematic perspective view
showing the configuration of the strain sensing element 200 according to the first embodiment.
As shown in FIG. 4, the strain sensing element 200 according to the present embodiment
includes the first magnetic layer 201, the second magnetic layer 202, and the space between the
first magnetic layer 201 and the second magnetic layer 202. It has the intermediate layer 203
provided. Each of the first magnetic layer 201 and the second magnetic layer 202 has
magnetization, and is disposed to be separated from each other via the intermediate layer 203.
[0026]
When strain occurs in the strain sensing element 200, the direction of the magnetization of at
least one of the magnetic layers 201 and 202 changes relative to the magnetization of the other.
Along with this, the electrical resistance value between the magnetic layers 201 and 202
changes. Therefore, the distortion generated in the strain sensing element 200 can be detected
by detecting the change in the electric resistance value.
[0027]
In the present embodiment, the first magnetic layer 201 is made of a ferromagnetic material and
functions, for example, as a magnetization free layer. The second magnetic layer 202 is also
made of a ferromagnetic material, and functions as, for example, a reference layer. The second
magnetic layer 202 may be a magnetization fixed layer or a magnetization free layer. That is, the
change of the magnetization of the first magnetic layer 201 may be easier than the change of the
magnetization of the second magnetic layer 203.
[0028]
For example, the first magnetic layer 201 can be formed larger in the XY plane than the second
magnetic layer 202. It is also possible to divide one of the first magnetic layer 201 and the
second magnetic layer 202.
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[0029]
Next, the operation of the strain sensing element 200 according to the present embodiment will
be described.
[0030]
FIG. 5A to FIG. 5C are schematic perspective views illustrating the operation of the strain sensing
element 200 according to the first embodiment.
FIG. 5A corresponds to a state (tensile state) when a tensile force ts is applied to the strain
sensing element 200 and a strain is generated. FIG. 5B corresponds to the state (non-distortion
state) when the strain sensing element 200 has no strain. FIG. 5C corresponds to a state (a
compressed state) when the strain sensing element 200 is applied with a compressive force cs
and a strain occurs.
[0031]
In FIG. 5A to FIG. 5C, the first magnetic layer 201, the second magnetic layer 202, and the
intermediate layer 203 are drawn in order to make the figure easy to see. In this example, the
first magnetic layer 201 is a magnetization free layer, and the second magnetic layer 202 is a
magnetization fixed layer.
[0032]
The operation in which the strain sensing element 200 functions as a strain sensor is based on
the application of the “inverse magnetostrictive effect” and the “magnetoresistive effect”.
The "inverse magnetostrictive effect" is obtained in the ferromagnetic layer used for the
magnetization free layer. The “magnetoresistive effect” appears in a laminated film of a
magnetization free layer, an intermediate layer, and a reference layer (for example, a
magnetization fixed layer).
[0033]
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The “inverse magnetostrictive effect” is a phenomenon in which the magnetization of a
ferromagnetic material changes due to the strain generated in the ferromagnetic material. That
is, when an external strain is applied to the stack of strain sensing elements, the magnetization
direction of the magnetization free layer changes. As a result, the relative angle between the
magnetization of the magnetization free layer and the magnetization of the reference layer (e.g.,
the magnetization fixed layer) changes. At this time, a change in electrical resistance is caused by
the “magnetoresistive effect (MR effect)”. The MR effect includes, for example, a GMR (Giant
magnetoresistance) effect or a TMR (Tunneling magnetoresistance) effect. By passing a current
through the stack, the MR effect is expressed by reading the change in the relative angle of the
direction of magnetization as the change in electrical resistance. For example, strain occurs in the
laminate (strain detection element), and the direction of magnetization of the magnetization free
layer changes due to the strain, and the direction of magnetization of the magnetization free
layer and the direction of magnetization of the reference layer (for example, magnetization fixed
layer) The relative angle of That is, the MR effect appears due to the inverse magnetostrictive
effect.
[0034]
When the ferromagnetic material used for the magnetization free layer has a positive
magnetostriction constant, the angle between the direction of magnetization and the direction of
tensile strain decreases, and the angle between the direction of magnetization and the direction
of compressive strain increases. , The direction of magnetization changes. When the
ferromagnetic material used for the magnetization free layer has a negative magnetostriction
constant, the angle between the direction of magnetization and the direction of tensile strain
increases, and the angle between the direction of magnetization and the direction of compressive
strain decreases. , The direction of magnetization changes.
[0035]
When the combination of the materials of the lamination of the magnetization free layer, the
intermediate layer and the reference layer (for example, the magnetization fixed layer) has a
positive magnetoresistance effect, the electrical resistance is obtained when the relative angle
between the magnetization free layer and the magnetization fixed layer is small. Decreases. When
the combination of the materials of the lamination of the magnetization free layer, the
intermediate layer and the reference layer (for example, the magnetization fixed layer) has a
negative magnetoresistance effect, the electrical resistance is obtained when the relative angle
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between the magnetization free layer and the magnetization fixed layer is small. Increases.
[0036]
Hereinafter, the ferromagnetic materials used for the magnetization free layer and the reference
layer (for example, the magnetization fixed layer) respectively have positive magnetostriction
constants, and the magnetization free layer, the intermediate layer, and the reference layer (for
example, the magnetization fixed layer) An example of the change in magnetization will be
described with respect to an example in the case where the stack including Y has a positive
magnetoresistance effect.
[0037]
As shown in FIG. 5B, in the strain-free non-strained state STo (eg, initial state), the magnetization
of the first magnetic layer (magnetization free layer) 201 and the second magnetic layer (eg,
magnetization fixed) The relative angle between the magnetization of the layer 202 and that of
the layer 202 is set to a predetermined value.
The magnetization direction of the magnetic layer in the initial state of the first magnetic layer
201 is set, for example, by hard bias or shape anisotropy of the magnetic layer. At this time, as an
example of setting of the initial magnetization direction by the hard bias, setting of a direction
inclined approximately 45 degrees with respect to the direction to which stress is applied is a
preferable example. In consideration of widening the range, an angle of 30 to 60 degrees is
preferable. By doing this, it is possible to obtain an output signal that changes linearly whether
positive stress or negative stress occurs. In this example, the magnetization of the first magnetic
layer 201 and the magnetization of the second magnetic layer 202 cross each other in the initial
state.
[0038]
As shown in FIG. 5A, when a tensile force ts is applied in the tensile state STt, strain occurs in the
strain sensing element 200 according to the tensile force ts. At this time, the magnetization of the
first magnetic layer 201 in the tensile state STt changes from the non-strain state STo so that the
angle between the magnetization and the direction of the tensile force ts becomes smaller. In the
example shown in FIG. 5A, when the tensile force ts is applied, the relative between the
magnetization of the first magnetic layer 201 and the magnetization of the second magnetic
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layer 202 as compared to the unstrained state STo. The angle is smaller. Thereby, the electrical
resistance in the strain sensing element 200 is reduced compared to the electrical resistance in
the unstrained state STo.
[0039]
On the other hand, as shown in FIG. 5C, when the compressive force cs is applied in the
compressed state STc, the magnetization of the first magnetic layer 201 in the compressed state
STc is the magnetization and the direction of the compressive force cs. It changes from the
unstrained state STo so that the angle becomes large.
[0040]
In the example shown in FIG. 5C, when the compression force cs is applied, the relative between
the magnetization of the first magnetic layer 201 and the magnetization of the second magnetic
layer 202 as compared to the unstrained state STo. The angle increases.
Thereby, the electrical resistance in the strain sensing element 200 is increased.
[0041]
Thus, in the strain sensing element 200, a change in strain generated in the strain sensing
element 200 is converted into a change in electric resistance of the strain sensing element 200.
In the above operation, the amount of change in electrical resistance (dR / R) per unit strain (dε)
is referred to as a gauge factor (GF). By using a strain sensing element with a high gauge factor, a
highly sensitive strain sensor can be obtained.
[0042]
Next, a configuration example of the strain sensing element 200 according to the present
embodiment will be described with reference to FIGS. In the following, the description of
“material A / material B” indicates a state in which the layer of material B is provided on the
layer of material A. FIG. 6 is a schematic perspective view showing a configuration example 200A
of the strain sensing element 200. As shown in FIG. As shown in FIG. 6, the strain sensing
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element 200A includes the lower electrode 204, the underlayer 205, the pinning layer 206, the
second magnetization fixed layer 207, the magnetic coupling layer 208, and the first
magnetization fixed layer 209 (second The magnetic layer 202), the intermediate layer 203, the
magnetization free layer 210 (first magnetic layer 201), the cap layer 211, and the upper
electrode 212 are sequentially stacked from the bottom. The first magnetization fixed layer 209
corresponds to the second magnetic layer 202. The magnetization free layer 210 corresponds to
the first magnetic layer 201. The lower electrode 204 is connected to, for example, the wiring C1
(FIG. 1), and the upper electrode 212 is connected to, for example, the wiring C2 (FIG. 1).
However, for example, when the first magnetic layer 201 is divided, the upper electrode
connected to one of the first magnetic layers 201 is connected to the wiring C1 (FIG. 1), and the
other first magnetic layer is connected. The upper electrode connected to 201 may be connected
to the wiring C2 (FIG. 1). Similarly, for example, when the second magnetic layer 202 is divided,
the lower electrode connected to one of the second magnetic layers 202 is connected to the
wiring C1 (FIG. 1), and the other second magnetic layer is separated. The lower electrode
connected to the layer 202 may be connected to the wiring C2 (FIG. 1).
[0043]
For the base layer 205, for example, a laminated film (Ta / Ru) of tantalum and ruthenium is
used. The thickness (length in the Z-axis direction) of this Ta layer is, for example, 3 nanometers
(nm). The thickness of this Ru layer is, for example, 2 nm. For the pinning layer 206, for example,
an IrMn layer with a thickness of 7 nm is used. For the second magnetization fixed layer 207, for
example, a Co 75 Fe 25 layer with a thickness of 2.5 nm is used. For the magnetic coupling layer
208, for example, a Ru layer with a thickness of 0.9 nm is used. For the first magnetization fixed
layer 209, for example, a Co 40 Fe 40 B 20 layer with a thickness of 3 nm is used. For the
intermediate layer 203, for example, an MgO layer having a thickness of 1.6 nm is used. For the
magnetization free layer 210, for example, 4 nm thick Co 40 Fe 40 B 20 is used. For the cap
layer 211, for example, Ta / Ru is used. The thickness of this Ta layer is, for example, 1 nm. The
thickness of this Ru layer is, for example, 5 nm.
[0044]
For the lower electrode 204 and the upper electrode 212, for example, at least one of aluminum
(Al), aluminum-copper alloy (Al-Cu), copper (Cu), silver (Ag), and gold (Au) is used. By using such
a material having a relatively small electric resistance as the lower electrode 204 and the upper
electrode 212, current can be efficiently supplied to the strain sensing element 200A.
Nonmagnetic materials can be used for the lower electrode 204 and the upper electrode 212.
04-05-2019
15
[0045]
The lower electrode 204 and the upper electrode 212 are, for example, an underlayer (not
shown) for the lower electrode 204 and the upper electrode 212, a cap layer (not shown) for the
lower electrode 204 and the upper electrode 212, and the like And at least one layer of Al, Al-Cu,
Cu, Ag, and Au. For example, tantalum (Ta) / copper (Cu) / tantalum (Ta) or the like is used for
the lower electrode 204 and the upper electrode 212. By using Ta as a base layer of the lower
electrode 204 and the upper electrode 212, for example, the adhesion between the substrate
210 and the lower electrode 204 and the upper electrode 212 is improved. As a base layer for
the lower electrode 204 and the upper electrode 212, titanium (Ti), titanium nitride (TiN), or the
like may be used.
[0046]
By using Ta as a cap layer of the lower electrode 204 and the upper electrode 212, oxidation of
copper (Cu) or the like under the cap layer can be prevented. As a cap layer for the lower
electrode 204 and the upper electrode 212, titanium (Ti), titanium nitride (TiN) or the like may
be used.
[0047]
For the base layer 205, for example, a stacked structure including a buffer layer (not shown) and
a seed layer (not shown) can be used. The buffer layer relieves, for example, the surface
roughness of the lower electrode 204, the film portion 120, and the like, and improves the
crystallinity of the layer stacked on the buffer layer. The buffer layer is, for example, at least one
selected from the group consisting of tantalum (Ta), titanium (Ti), vanadium (V), tungsten (W),
zirconium (Zr), hafnium (Hf) and chromium (Cr). Is used. As the buffer layer, an alloy containing
at least one material selected from these materials may be used.
[0048]
The thickness of the buffer layer in the base layer 205 is preferably 1 nm or more and 10 nm or
04-05-2019
16
less. The thickness of the buffer layer is more preferably 1 nm or more and 5 nm or less. If the
thickness of the buffer layer is too thin, the buffer effect is lost. When the thickness of the buffer
layer is too thick, the thickness of the strain sensing element 200A becomes excessively thick. A
seed layer is formed on the buffer layer, and the seed layer can have a buffer effect. In this case,
the buffer layer may be omitted. For the buffer layer, for example, a Ta layer having a thickness
of 3 nm is used.
[0049]
The seed layer in the base layer 205 controls the crystal orientation of the layer stacked on the
seed layer. The seed layer controls the grain size of the layer laminated on the seed layer. As this
seed layer, fcc structure (face-centered cubic structure: face-centered cubic lattice structure), hcp
structure (hexagonal close-packed structure: hexagonal close-packed lattice structure) or bcc
structure (body-centered cubic structure: body-centered cubic lattice) Metal of the structure) is
used.
[0050]
By using ruthenium (Ru) of hcp structure, NiFe of fcc structure, or Cu of fcc structure as the seed
layer of the underlayer 205, for example, the crystal orientation of the spin valve film on the seed
layer is determined. It can be fcc (111) oriented. For the seed layer, for example, a Cu layer with a
thickness of 2 nm or a Ru layer with a thickness of 2 nm is used. When the crystal orientation of
the layer formed on the seed layer is to be enhanced, the thickness of the seed layer is preferably
1 nm or more and 5 nm or less. The thickness of the seed layer is more preferably 1 nm or more
and 3 nm or less. Thereby, the function as a seed layer which improves crystal orientation is fully
exhibited.
[0051]
On the other hand, for example, when it is not necessary to crystallize the layer formed on the
seed layer (for example, when forming an amorphous magnetization free layer), the seed layer
may be omitted. As a seed layer, for example, a Cu layer having a thickness of 2 nm is used.
[0052]
04-05-2019
17
The pinning layer 206 applies unidirectional anisotropy (unidirectional anisotropy) to the second
magnetization fixed layer 207 (ferromagnetic layer) formed on the pinning layer 206, for
example. Fix the magnetization. For the pinning layer 206, for example, an antiferromagnetic
layer is used. For the pinning layer 206, for example, Ir-Mn, Pt-Mn, Pd-Pt-Mn, Ru-Mn, Rh-Mn, RuRh-Mn, Fe-Mn, Ni-Mn, Cr-Mn-Pt and At least one selected from the group consisting of Ni-O is
used. Additional elements to Ir-Mn, Pt-Mn, Pd-Pt-Mn, Ru-Mn, Rh-Mn, Ru-Rh-Mn, Fe-Mn, Ni-Mn,
Cr-Mn-Pt and Ni-O You may use the added alloy. The thickness of the pinning layer 206 is
appropriately set to impart sufficient strength of unidirectional anisotropy.
[0053]
In order to fix the magnetization of the ferromagnetic layer in contact with the pinning layer 206,
heat treatment is performed while applying a magnetic field. The magnetization of the
ferromagnetic layer in contact with the pinning layer 206 is fixed in the direction of the magnetic
field applied during the heat treatment. The annealing temperature is, for example, equal to or
higher than the magnetization fixation temperature of the antiferromagnetic material used for
the pinning layer 206. When an antiferromagnetic layer containing Mn is used, Mn may be
diffused in layers other than the pinning layer 206 to reduce the MR ratio. Therefore, it is
desirable to set it below the temperature which diffusion of Mn occurs. For example, the
temperature can be set to 200 degrees (° C.) or more and 500 degrees (° C.) or less.
Preferably, it can be 250 degrees (degree C) or more and 400 degrees (degree C) or less.
[0054]
When PtMn or PdPtMn is used as the pinning layer 206, the thickness of the pinning layer 206
is preferably 8 nm or more and 20 nm or less. The thickness of the pinning layer 206 is more
preferably 10 nm or more and 15 nm or less. When IrMn is used as the pinning layer 206,
unidirectional anisotropy can be imparted with a thinner thickness than when PtMn is used as
the pinning layer 206. In this case, the thickness of the pinning layer 206 is preferably 4 nm or
more and 18 nm or less. The thickness of the pinning layer 206 is more preferably 5 nm or more
and 15 nm or less. For the pinning layer 206, for example, an Ir 22 Mn 78 layer with a thickness
of 7 nm is used.
[0055]
04-05-2019
18
A hard magnetic layer may be used as the pinning layer 206. As the hard magnetic layer, for
example, a hard magnetic material having relatively high magnetic anisotropy and coercivity
such as Co-Pt, Fe-Pt, Co-Pd, and Fe-Pd is used. Alternatively, an alloy in which an additive element
is further added to Co-Pt, Fe-Pt, Co-Pd, or Fe-Pd may be used. For example, CoPt (Co ratio is 50
at. % Or more and 85 at. % Or less), (CoxPt100-x) 100-yCry (x is 50 at. % Or more and 85 at. % Or
less, y is 0 at. % Or more 40 at. % Or less) or FePt (the ratio of Pt is 40 at. % Or more 60 at. %) Or
the like may be used.
[0056]
In the second magnetization fixed layer 207, for example, a Co x Fe 100-x alloy (x is 0 at. % To
100 at. % Or less), Ni x Fe 100-x alloy (x is 0 at. % To 100 at. Or less, or materials obtained by
adding a nonmagnetic element thereto. As the second magnetization fixed layer 207, for
example, at least one selected from the group consisting of Co, Fe, and Ni is used. As the second
magnetization fixed layer 207, an alloy containing at least one material selected from these
materials may be used. As the second magnetization fixed layer 207, a (CoxFe100-x) 100-yBy
alloy (x is 0 at. % To 100 at. % Or less, y is 0 at. % To 30 at. % Or less) can also be used. By using
an amorphous alloy of (Co x Fe 100 -x) 100 -y B y as the second magnetization fixed layer 207,
the variation in the characteristics of the strain sensing element 100a can be suppressed even
when the size of the strain sensing element is small. be able to.
[0057]
The thickness of the second magnetization fixed layer 207 is preferably, for example, 1.5 nm or
more and 5 nm or less. Thereby, for example, the strength of the unidirectional anisotropic
magnetic field by the pinning layer 206 can be made stronger. For example, increasing the
strength of the antiferromagnetic coupling magnetic field between the second magnetization
fixed layer 207 and the first magnetization fixed layer 209 via the magnetic coupling layer
formed on the second magnetization fixed layer 207. Can. For example, it is preferable that the
magnetic film thickness of the second magnetization fixed layer 207 (product of saturated
magnetization Bs and thickness t (Bs · t)) be substantially equal to the magnetic film thickness of
the first magnetization fixed layer 209 .
[0058]
04-05-2019
19
The saturation magnetization of Co 40 Fe 40 B 20 in a thin film is about 1.9 T (Tesla). For
example, when a 3 nm thick Co 40 Fe 40 B 20 layer is used as the first magnetization fixed layer
209, the magnetic thickness of the first magnetization fixed layer 209 is 1.9 T × 3 nm, 5.7 T nm,
Become. On the other hand, the saturation magnetization of Co 75 Fe 25 is about 2.1 T. The
thickness of the second magnetization fixed layer 207 at which the magnetic film thickness equal
to the above is obtained is 5.7 Tnm / 2.1T, which is 2.7 nm. In this case, as the second
magnetization fixed layer 207, it is preferable to use a Co 75 Fe 25 layer having a thickness of
about 2.7 nm. As the second magnetization fixed layer 207, for example, a Co 75 Fe 25 layer
with a thickness of 2.5 nm is used.
[0059]
In the strain sensing element 200A, a synthetic pin structure is used by the second magnetization
fixed layer 207, the magnetic coupling layer 208, and the first magnetization fixed layer 209.
Instead of this, a single pin structure consisting of one magnetization fixed layer may be used.
When a single pin structure is used, for example, a Co 40 Fe 40 B 20 layer with a thickness of 3
nm is used as the magnetization fixed layer. The same material as the material of the second
magnetization fixed layer 207 described above may be used as the ferromagnetic layer used for
the magnetization fixed layer of the single pin structure.
[0060]
The magnetic coupling layer 208 causes antiferromagnetic coupling between the second
magnetization fixed layer 207 and the first magnetization fixed layer 209. The magnetic coupling
layer 208 forms a synthetic pin structure. As a material of the magnetic coupling layer 208, for
example, Ru is used. The thickness of the magnetic coupling layer 208 is preferably, for example,
0.8 nm or more and 1 nm or less. A material other than Ru may be used as the magnetic coupling
layer 208 as long as it is a material that causes sufficient antiferromagnetic coupling between the
second magnetization fixed layer 207 and the first magnetization fixed layer 209. The thickness
of the magnetic coupling layer 208 can be set to a thickness greater than or equal to 0.8 nm and
less than or equal to 1 nm, which corresponds to a second peak (2nd peak) of RKKY (RudermanKittel-Kasuya-Yosida) bonding. Furthermore, the thickness of the magnetic coupling layer 208
may be set to a thickness of 0.3 nm or more and 0.6 nm or less corresponding to the first peak
(1st peak) of the RKKY bond. As a material of the magnetic coupling layer 208, for example, Ru
having a thickness of 0.9 nm is used. Thereby, a reliable connection can be obtained more stably.
04-05-2019
20
[0061]
The magnetic layer used for the first magnetization fixed layer 209 (second magnetic layer 202)
directly contributes to the MR effect. As the first magnetization fixed layer 209, for example, a
Co-Fe-B alloy is used. Specifically, as the first magnetization fixed layer 209, a (CoxFe100-x) 100yBy alloy (x is 0 at. % To 100 at. % Or less, y is 0 at. % To 30 at. % Or less) can also be used.
When an amorphous alloy of (CoxFe100-x) 100-yBy is used as the first magnetization fixed layer
209, for example, even when the size of the strain sensing element 200A is small, it is attributed
to crystal grains. Variations between elements can be suppressed.
[0062]
A layer (for example, a tunnel insulating layer (not shown)) formed on the first magnetization
fixed layer 209 can be planarized. Planarization of the tunnel insulating layer can reduce the
defect density of the tunnel insulating layer. This results in a higher MR ratio with lower areal
resistance. For example, in the case of using MgO as the material of the tunnel insulating layer, it
is possible to use an amorphous alloy of (CoxFe100-x) 100-yBy as the first magnetization fixed
layer 209 on the tunnel insulating layer. The (100) orientation of the MgO layer to be formed can
be intensified. By making the (100) orientation of the MgO layer higher, a larger MR change rate
can be obtained. The (Co x Fe 100 -x) 100 -y B y alloy crystallizes with the (100) plane of the
MgO layer as a template during annealing. Therefore, good crystal matching between MgO and
the (CoxFe100-x) 100-yBy alloy can be obtained. By obtaining a good crystal alignment, a larger
MR ratio can be obtained. As the first magnetization fixed layer 209, for example, an Fe-Co alloy
may be used other than the Co-Fe-B alloy.
[0063]
When the first magnetization fixed layer 209 is thicker, a larger MR ratio is obtained. In order to
obtain a larger fixed magnetic field, it is preferable that the first magnetization fixed layer 209 be
thin. There is a trade-off relationship in the thickness of the first magnetization fixed layer 209
between the MR ratio and the fixed magnetic field. When a Co̶Fe̶B alloy is used as the first
magnetization fixed layer 209, the thickness of the first magnetization fixed layer 209 is
preferably 1.5 nm or more and 5 nm or less. The thickness of the first magnetization fixed layer
04-05-2019
21
209 is more preferably 2.0 nm or more and 4 nm or less.
[0064]
For the first magnetization fixed layer 209, in addition to the above-described materials, a Co 90
Fe 10 alloy of fcc structure, Co of hcp structure, or Co alloy of hcp structure is used. As the first
magnetization fixed layer 209, for example, at least one selected from the group consisting of Co,
Fe, and Ni is used. As the first magnetization fixed layer 209, an alloy containing at least one
material selected from these materials is used. By using, as the first magnetization fixed layer
209, a FeCo alloy material of bcc structure, a Co alloy containing 50% or more of cobalt
composition, or a material of 50% or more of Ni composition (Ni alloy), for example, a larger MR
The rate of change is obtained.
[0065]
As the first magnetization fixed layer 209, for example, Co 2 MnGe, Co 2 FeGe, Co 2 MnSi, Co 2
FeSi, Co 2 MnAl, Co 2 FeAl, Co 2 MnGa 0.5 Ge 0.5, and Co 2 FeGa A Heusler magnetic alloy layer
such as 0.5 Ge 0.5 can also be used. For example, a Co 40 Fe 40 B 20 layer with a thickness of 3
nm is used as the first magnetization fixed layer 209, for example.
[0066]
The intermediate layer 203 cuts off the magnetic coupling between the first magnetic layer 201
and the second magnetic layer 202, for example. As a material of the intermediate layer 203, for
example, a metal, an insulator or a semiconductor is used. As the metal, for example, Cu, Au or Ag
is used. When a metal is used as the intermediate layer 203, the thickness of the intermediate
layer is, for example, about 1 nm or more and 7 nm or less. As this insulator or semiconductor,
for example, magnesium oxide (such as MgO), aluminum oxide (such as Al2O3), titanium oxide
(such as TiO), zinc oxide (such as ZnO), or gallium oxide (such as Ga- O) etc. are used. When an
insulator or a semiconductor is used as the intermediate layer 203, the thickness of the
intermediate layer 203 is, for example, about 0.6 nm or more and 2.5 nm or less. As the
intermediate layer 203, for example, a CCP (Current-Confined-Path) spacer layer may be used.
When a CCP spacer layer is used as a spacer layer, for example, a structure in which a copper
(Cu) metal path is formed in an insulating layer of aluminum oxide (Al 2 O 3) is used. For
example, a MgO layer with a thickness of 1.6 nm is used as the intermediate layer.
04-05-2019
22
[0067]
A ferromagnetic material is used for the magnetization free layer 210 (first magnetic layer 201).
For the magnetization free layer 210, for example, a ferromagnetic material containing Fe, Co, Ni
can be used. As a material of the magnetization free layer 210, for example, a FeCo alloy, a NiFe
alloy or the like is used. Furthermore, in the magnetization free layer 210, a Co-Fe-B alloy, an FeCo-Si-B alloy, an Fe-Ga alloy having a large λs (magnetostriction constant), an Fe-Co-Ga alloy, a
Tb-M-Fe alloy , Tb-M1-Fe-M2 alloy, Fe-M3-M4-B alloy, Ni, Fe-Al, or ferrite is used. In the
aforementioned Tb-M-Fe alloy, M is at least one selected from the group consisting of Sm, Eu, Gd,
Dy, Ho and Er. In the above-described Tb-M1-Fe-M2 alloy, M1 is at least one selected from the
group consisting of Sm, Eu, Gd, Dy, Ho and Er. M2 is at least one selected from the group
consisting of Ti, Cr, Mn, Co, Cu, Nb, Mo, W and Ta. In the above-described Fe-M3-M4-B alloy, M3
is at least one selected from the group consisting of Ti, Cr, Mn, Co, Cu, Nb, Mo, W, and Ta. M4 is
at least one selected from the group consisting of Ce, Pr, Nd, Sm, Tb, Dy and Er. Examples of the
above-mentioned ferrite include Fe 3 O 4 and (FeCo) 3 O 4. The thickness of the magnetization
free layer 210 is, for example, 2 nm or more.
[0068]
For the magnetization free layer 210, a magnetic material containing boron may be used. For the
magnetization free layer 210, for example, an alloy containing at least one element selected from
the group consisting of Fe, Co and Ni and boron (B) may be used. For example, a Co-Fe-B alloy or
an Fe-B alloy can be used. For example, a Co40Fe40B20 alloy can be used. When an alloy
containing at least one element selected from the group consisting of Fe, Co and Ni and boron (B)
is used for the magnetization free layer 210, Ga, Al, Si, as an element promoting high
magnetostriction Alternatively, W or the like may be added. For example, an Fe-Ga-B alloy, an FeCo-Ga-B alloy, or an Fe-Co-Si-B alloy may be used. By using such a boron-containing magnetic
material, the coercivity (Hc) of the magnetization free layer 210 becomes low, and the change of
the magnetization direction with respect to strain becomes easy. Thereby, high distortion
sensitivity can be obtained.
[0069]
The boron concentration (for example, the composition ratio of boron) in the magnetization free
04-05-2019
23
layer 210 is 5 at. % (Atomic percent) or more is preferable. This makes it easy to obtain an
amorphous structure. The boron concentration in the magnetization free layer is 35 at. % Or less
is preferable. If the boron concentration is too high, for example, the magnetostriction constant
decreases. The boron concentration in the magnetization free layer is, for example, 5 at. % Or
more 35 at. % Or less is preferable, and 10 at. % To 30 at. % Or less is more preferable.
[0070]
In a part of the magnetic layer of the magnetization free layer 210, Fe 1-y B y (0 <y ≦ 0.3), or (Fe
a X 1-a) 1-y B y (X = Co or Ni, 0) When 8 ≦ a <1, 0 <y ≦ 0.3, it is particularly preferable from
the viewpoint of obtaining a high gauge factor because it is easy to simultaneously achieve a
large magnetostriction constant λ and a low coercivity. For example, Fe 80 B 20 (4 nm) can be
used as the magnetization free layer 210. Co 40 Fe 40 B 20 (0.5 nm) / Fe 80 B 20 (4 nm) can be
used as the magnetization free layer.
[0071]
The magnetization free layer 210 may have a multilayer structure. When a tunnel insulating
layer of MgO is used as the intermediate layer 203, a layer of a Co-Fe-B alloy is preferably
provided in a portion of the magnetization free layer 210 in contact with the intermediate layer
203. Thereby, a high magnetoresistance effect can be obtained. In this case, a layer of a Co-Fe-B
alloy is provided on the intermediate layer 203, and another magnetic material having a large
magnetostriction constant is provided on the layer of the Co-Fe-B alloy. When the magnetization
free layer 210 has a multilayer structure, for example, Co-Fe-B (2 nm) / Fe-Co-Si-B (4 nm) or the
like is used for the magnetization free layer 210.
[0072]
The cap layer 211 protects a layer provided under the cap layer 211. For the cap layer 211, for
example, a plurality of metal layers are used. For the cap layer 211, for example, a two-layer
structure (Ta / Ru) of a Ta layer and a Ru layer is used. The thickness of this Ta layer is, for
example, 1 nm, and the thickness of this Ru layer is, for example, 5 nm. As the cap layer 211,
another metal layer may be provided instead of the Ta layer or the Ru layer. The configuration of
the cap layer 211 is arbitrary. For example, a nonmagnetic material can be used for the cap layer
211. Other materials may be used as the cap layer 211 as long as the layer provided below the
04-05-2019
24
cap layer 211 can be protected.
[0073]
When using a magnetic material containing boron for the magnetization free layer 210, a
diffusion prevention layer (not shown) of an oxide material or nitride material is provided
between the magnetization free layer 210 and the cap layer 211 in order to prevent the diffusion
of boron. Also good. By using a diffusion prevention layer formed of an oxide layer or a nitride
layer, diffusion of boron contained in the magnetization free layer 210 can be suppressed, and
the amorphous structure of the magnetization free layer 211 can be maintained. Specifically, Mg,
Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru are used as the oxide material and the
nitride material used for the diffusion prevention layer. An oxide material or nitride material
containing an element such as Rh, Pd, Ag, Hf, Ta, W, Sn, Cd, or Ga can be used.
[0074]
Here, since the diffusion prevention layer is a layer that does not contribute to the
magnetoresistance effect, it is preferable that the area resistance be low. For example, the area
resistance of the diffusion prevention layer is preferably set lower than the area resistance of the
intermediate layer contributing to the magnetoresistive effect. From the viewpoint of reducing
the area resistance of the diffusion preventing layer, an oxide or a nitride of Mg, Ti, V, Zn, Sn, Cd,
or Ga having a low barrier height is preferable. As a function to suppress the diffusion of boron,
an oxide having a stronger chemical bond is preferable. For example, 1.5 nm of MgO can be used.
Also, the oxynitride can be considered as either an oxide or a nitride.
[0075]
When using an oxide material or a nitride material for the diffusion prevention layer, the film
thickness of the diffusion prevention layer is preferably 0.5 nm or more from the viewpoint of
sufficiently exerting the diffusion preventing function of boron, and 5 nm from the viewpoint of
lowering area resistance. The following are preferred. That is, the film thickness of the diffusion
prevention layer is preferably 0.5 nm or more and 5 nm or less, and more preferably 1 nm or
more and 3 nm or less.
04-05-2019
25
[0076]
As the diffusion preventing layer, at least one selected from the group consisting of magnesium
(Mg), silicon (Si) and aluminum (Al) can be used. As the diffusion preventing layer, materials
containing these light elements can be used. These light elements combine with boron to form a
compound. For example, at least one of a Mg-B compound, an Al-B compound, and a Si-B
compound is formed in a portion including the interface between the diffusion prevention layer
and the magnetization free layer 210. These compounds suppress the diffusion of boron.
[0077]
Another metal layer or the like may be inserted between the diffusion prevention layer and the
magnetization free layer 210. However, if the distance between the diffusion prevention layer
and the magnetization free layer 210 is too large, boron diffuses between them and the boron
concentration in the magnetization free layer 210 decreases, so the diffusion prevention layer
and the magnetization free layer 210 10 nm or less is preferable and 3 nm or less is further
more preferable.
[0078]
FIG. 7 is a schematic perspective view showing a configuration example of the strain sensing
element 200A. As illustrated in FIG. 7, the strain sensing element 200 </ b> A may include an
insulating layer (insulating portion) 213 filled between the lower electrode 204 and the upper
electrode 212.
[0079]
For the insulating layer 213, for example, aluminum oxide (eg, Al 2 O 3), silicon oxide (eg, SiO 2),
or the like can be used. The insulating layer 213 can suppress the leak current of the strain
sensing element 200A.
[0080]
04-05-2019
26
FIG. 8 is a schematic perspective view showing another configuration example of the strain
sensing element 200A. As illustrated in FIG. 8, the strain sensing element 200 </ b> A includes
two hard bias layers (hard bias portions) 214 and a lower electrode 204 provided apart from
each other between the lower electrode 204 and the upper electrode 212. An insulating layer
213 filled between the hard bias layers 214 may be provided.
[0081]
The hard bias layer 214 sets the magnetization direction of the magnetization free layer 210
(first magnetic layer 201) to a desired direction by the magnetization of the hard bias layer 214.
With the hard bias layer 214, the magnetization direction of the magnetization free layer 210
(first magnetic layer 201) can be set to a desired direction in a state where external pressure is
not applied to the film portion.
[0082]
For the hard bias layer 214, for example, a hard magnetic material having relatively high
magnetic anisotropy and coercivity such as Co-Pt, Fe-Pt, Co-Pd, and Fe-Pd is used. Alternatively,
an alloy in which an additive element is further added to Co-Pt, Fe-Pt, Co-Pd, or Fe-Pd may be
used. For example, CoPt (Co ratio is 50 at. % Or more and 85 at. % Or less), (CoxPt100-x) 100yCry (x is 50 at. % Or more and 85 at. % Or less, y is 0 at. % Or more 40 at. % Or less) or FePt (the
ratio of Pt is 40 at. % Or more 60 at. %) Or the like may be used. When such a material is used,
the magnetization direction of the hard bias layer 214 can be set (fixed) in the direction in which
the external magnetic field is applied by applying an external magnetic field larger than the
coercivity of the hard bias layer 214. . The thickness (for example, the length along the direction
from the lower electrode 204 toward the upper electrode) of the hard bias layer 214 is, for
example, 5 nm or more and 50 nm or less.
[0083]
When the insulating layer 213 is disposed between the lower electrode 204 and the upper
electrode 212, SiO x or AlO x can be used as a material of the insulating layer 213. Furthermore,
an underlayer (not shown) may be provided between the insulating layer 213 and the hard bias
layer 214. When a hard magnetic material such as Co-Pt, Fe-Pt, Co-Pd, Fe-Pd or the like having a
04-05-2019
27
relatively high magnetic anisotropy and coercive force is used for the hard bias layer 214, an
underlayer for the hard bias layer 214 Cr, Fe-Co, etc. can be used as the material of The hard bias
layer 214 described above can be applied to any strain sensing element described later.
[0084]
The hard bias layer 214 may have a structure stacked on a hard bias layer pinning layer (not
shown). In this case, the magnetization direction of the hard bias layer 214 can be set (fixed) by
exchange coupling between the hard bias layer 214 and the pinning layer for hard bias layer. In
this case, for the hard bias layer 214, a ferromagnetic material made of an alloy containing at
least one of Fe, Co and Ni, or at least one of them can be used. In this case, for the hard bias layer
214, for example, a Co x Fe 100-x alloy (x is 0 at. % To 100 at. % Or less), Ni x Fe 100-x alloy (x is
0 at. % To 100 at. % Or less) or materials obtained by adding a nonmagnetic element thereto can
be used. As the hard bias layer 214, the same material as that of the first magnetization fixed
layer 209 described above can be used. Further, for the hard bias layer pinning layer, the same
material as the pinning layer 206 in the strain sensing element 200A described above can be
used. In the case of providing a hard bias layer pinning layer, an underlying layer similar to the
material used for the underlying layer 205 may be provided below the hard bias layer pinning
layer. The hard bias layer pinning layer may be provided below or above the hard bias layer. The
magnetization direction of the hard bias layer 214 in this case can be determined by heat
treatment in a magnetic field, as with the pinning layer 206.
[0085]
The hard bias layer 214 and the insulating layer 213 described above can be applied to any of
the strain sensing elements 200A described in this embodiment. Further, in the case of using the
above-described stacked structure of the hard bias layer 214 and the hard bias layer pinning
layer, the magnetization of the hard bias layer 214 may be changed even when a large external
magnetic field is instantaneously applied to the hard bias layer 214. The orientation can be easily
maintained.
[0086]
FIG. 9 is a schematic perspective view showing another configuration example 200B of the strain
sensing element 200. As shown in FIG. Unlike the strain sensing element 200A, the strain sensing
04-05-2019
28
element 200B has a top spin valve type structure. That is, as shown in FIG. 9, the strain sensing
element 200B includes the lower electrode 204, the underlayer 205, the magnetization free layer
210 (the first magnetic layer 201), the intermediate layer 203, and the first magnetization fixed
layer 209 (the first magnetization fixed layer). The second magnetic layer 202), the magnetic
coupling layer 208, the second magnetization fixed layer 207, the pinning layer 206, the cap
layer 211, and the upper electrode 212 are stacked in order from the bottom. The first
magnetization fixed layer 209 corresponds to the second magnetic layer 202. The magnetization
free layer 210 corresponds to the first magnetic layer 201. The lower electrode 204 is connected
to, for example, the wiring C1 (FIG. 1), and the upper electrode 212 is connected to, for example,
the wiring C2 (FIG. 1).
[0087]
As the base layer 205, for example, a laminated film (Ta / Cu) of tantalum and copper is used.
The thickness (length in the Z-axis direction) of this Ta layer is, for example, 3 nm. The thickness
of this Cu layer is, for example, 5 nm. For the magnetization free layer 210, for example, 4 nm
thick Co 40 Fe 40 B 20 is used. For the intermediate layer 203, for example, an MgO layer
having a thickness of 1.6 nm is used. For the first magnetization fixed layer 209, for example,
Co40Fe40B20 / Fe50Co50 is used. The thickness of this Co 40 Fe 40 B 20 layer is, for example,
2 nm. The thickness of this Fe 50 Co 50 layer is, for example, 1 nm. For the magnetic coupling
layer 208, for example, a Ru layer with a thickness of 0.9 nm is used. For the second
magnetization fixed layer 207, for example, a Co 75 Fe 25 layer with a thickness of 2.5 nm is
used. For the pinning layer 206, for example, an IrMn layer with a thickness of 7 nm is used. For
the cap layer 211, for example, Ta / Ru is used. The thickness of this Ta layer is, for example, 1
nm. The thickness of this Ru layer is, for example, 5 nm.
[0088]
In the bottom spin valve type strain sensing element 200A described above, the first
magnetization fixed layer 209 (second magnetic layer 202) is lower than the magnetization free
layer 210 (first magnetic layer 201) (-Z-axis direction) Is formed. On the other hand, in the top
spin valve type strain sensing element 200B, the first magnetization fixed layer 209 (second
magnetic layer 202) is higher than the magnetization free layer 210 (first magnetic layer 201)
(in the + Z-axis direction) Is formed. Therefore, the material of each layer included in the strain
sensing element 200B can be used by vertically inverting the material of each layer included in
the strain sensing element 200A. Further, the above-described diffusion preventing layer can be
provided between the underlayer 205 of the strain sensing element 200B and the magnetization
04-05-2019
29
free layer 210.
[0089]
FIG. 10 is a schematic perspective view showing another configuration example 200C of the
strain sensing element 200. As shown in FIG. The strain sensing element 200C has a single pin
structure using a single magnetization fixed layer. That is, as shown in FIG. 10, the strain sensing
element 200C includes the lower electrode 204, the underlayer 205, the pinning layer 206, the
first magnetization fixed layer 209 (second magnetic layer 202), and the intermediate layer 203.
A magnetization free layer 210 (first magnetic layer 201) and a cap layer 211 are sequentially
stacked. The first magnetization fixed layer 209 corresponds to the second magnetic layer 202.
The magnetization free layer 210 corresponds to the first magnetic layer 201. The lower
electrode 204 is connected to, for example, the wiring C1 (FIG. 1), and the upper electrode 212 is
connected to, for example, the wiring C2 (FIG. 1).
[0090]
For the base layer 205, for example, Ta / Ru is used. The thickness (length in the Z-axis direction)
of this Ta layer is, for example, 3 nm. The thickness of this Ru layer is, for example, 2 nm. For the
pinning layer 206, for example, an IrMn layer with a thickness of 7 nm is used. For the first
magnetization fixed layer 209, for example, a Co 40 Fe 40 B 20 layer with a thickness of 3 nm is
used. For the intermediate layer 203, for example, an MgO layer having a thickness of 1.6 nm is
used. For the magnetization free layer 210, for example, 4 nm thick Co 40 Fe 40 B 20 is used.
For the cap layer 211, for example, Ta / Ru is used. The thickness of this Ta layer is, for example,
1 nm. The thickness of this Ru layer is, for example, 5 nm. The material of each layer of the strain
sensing element 200C can be the same as the material of each layer of the strain sensing element
200A.
[0091]
FIG. 11 is a schematic perspective view showing another configuration example 200D of the
strain sensing element 200. As shown in FIG. As shown in FIG. 11, the strain sensing element
200D includes the lower electrode 204, the underlayer 205, the lower pinning layer 221, the
lower second magnetization fixed layer 222, the lower magnetic coupling layer 223, and the
lower first magnetization fixed layer. 224, lower intermediate layer 225, magnetization free layer
04-05-2019
30
226, upper intermediate layer 227, upper first magnetization fixed layer 228, upper magnetic
coupling layer 229, upper second magnetization fixed layer 230, upper pinning layer 231 And
the cap layer 211 in order. The lower first magnetization fixed layer 224 and the upper first
magnetization fixed layer 228 correspond to the second magnetic layer 202. The magnetization
free layer 226 corresponds to the first magnetic layer 201. The lower electrode 204 is connected
to, for example, the wiring C1 (FIG. 1), and the upper electrode 212 is connected to, for example,
the wiring C2 (FIG. 1).
[0092]
For the base layer 205, for example, Ta / Ru is used. The thickness (length in the Z-axis direction)
of this Ta layer is, for example, 3 nanometers (nm). The thickness of this Ru layer is, for example,
2 nm. For the lower pinning layer 221, for example, an IrMn layer with a thickness of 7 nm is
used. For the lower second magnetization fixed layer 222, for example, a Co 75 Fe 25 layer with
a thickness of 2.5 nm is used. For the lower magnetic coupling layer 223, for example, a Ru layer
with a thickness of 0.9 nm is used. For the lower first magnetization fixed layer 224, for example,
a Co 40 Fe 40 B 20 layer with a thickness of 3 nm is used. For the lower intermediate layer 225,
for example, an MgO layer having a thickness of 1.6 nm is used. For the magnetization free layer
226, for example, 4 nm thick Co 40 Fe 40 B 20 is used. For the upper intermediate layer 227, for
example, an MgO layer having a thickness of 1.6 nm is used. For the upper first magnetization
fixed layer 228, for example, Co40Fe40B20 / Fe50Co50 is used. The thickness of this Co 40 Fe
40 B 20 layer is, for example, 2 nm. The thickness of this Fe 50 Co 50 layer is, for example, 1 nm.
For the upper magnetic coupling layer 229, for example, a Ru layer with a thickness of 0.9 nm is
used. For the upper second magnetization fixed layer 230, for example, a Co 75 Fe 25 layer with
a thickness of 2.5 nm is used. For the upper pinning layer 231, for example, an IrMn layer with a
thickness of 7 nm is used. For the cap layer 211, for example, Ta / Ru is used. The thickness of
this Ta layer is, for example, 1 nm. The thickness of this Ru layer is, for example, 5 nm. The
material of each layer of the strain sensing element 200D can be the same as the material of each
layer of the strain sensing element 200A.
[0093]
FIG. 12 is a schematic perspective view showing a configuration example 200E of the strain
sensing element 200. As shown in FIG. As shown in FIG. 12, the strain sensing element 200E
includes the lower electrode 204, the underlayer 205, the first magnetization free layer 241 (the
first magnetic layer 201), the intermediate layer 203, and the second magnetization free layer
242 (the second magnetization free layer 242). The second magnetic layer 202), the cap layer
04-05-2019
31
211, and the upper electrode 212 are sequentially stacked. The first magnetization free layer
241 corresponds to the first magnetic layer 201. The second magnetization free layer 242
corresponds to the second magnetic layer 202. The lower electrode 204 is connected to, for
example, the wiring C1 (FIG. 1), and the upper electrode 212 is connected to, for example, the
wiring C2 (FIG. 1).
[0094]
For the base layer 205, for example, Ta / Cu is used. The thickness (length in the Z-axis direction)
of this Ta layer is, for example, 3 nm. The thickness of this Cu layer is, for example, 5 nm. For the
first magnetization free layer 241, for example, Co40Fe40B20 having a thickness of 4 nm is
used. For the intermediate layer 203, for example, Co40Fe40B20 with a thickness of 4 nm is
used in the second example. For example, Cu / Ta / Ru is used for the cap layer 211. The
thickness of this Cu layer is, for example, 5 nm. The thickness of this Ta layer is, for example, 1
nm. The thickness of this Ru layer is, for example, 5 nm.
[0095]
The material of each layer of the strain sensing element 200E can be the same as the material of
each layer of the strain sensing element 200A. Also, as a material of the first magnetization free
layer 241 and the second magnetization free layer 242, for example, the same material as the
magnetization free layer 210 of the strain sensing element 200A (FIG. 6) may be used.
[0096]
(Effects of the First Embodiment) The film portion 120 (the vibrating portion 121 and the
supported portion 122) of the first embodiment is an oxide (for example, oxidized) including
aluminum (Al). Formed of aluminum). As described above, the hollow portion 111 is formed by
etching the substrate 110 and processing the substrate 110 until the film portion 120 is
exposed. However, at that time, if the film portion 120 is etched, depending on the degree, the
film thickness of the exposed film portion 120 will differ depending on the place, whereby the
desired characteristics of the film portion 120 can not be obtained. There is a problem in that the
accuracy of the sensor 110A is reduced. This problem is described with reference to FIGS. 13A17.
04-05-2019
32
[0097]
FIG. 13A is a schematic view showing a problem in the process of processing the hollow portion
111 of the pressure sensor 110A of the first embodiment. In order to simplify the illustration,
only the sensing element 200 is displayed on the film portion 120, and the wiring and the like
are not displayed.
[0098]
The hollow portion 111 is formed by etching the substrate 110 by deep RIE. At the time of
processing, the etching gas and the substrate 110 are in contact with each other to cause a
chemical reaction to proceed the etching.
[0099]
The processing of the cavity portion 111 proceeds, and when the depth of the cavity portion is
increased, the accessibility of the etching gas 72 at the bottom of the cavity portion 111 is
different. In general, the etching gas 72 is less likely to reach the end portion compared to the
central portion of the hollow portion 111.
[0100]
As described above, when the cavity 111 is processed, the etching gas 72 easily reaches the
bottom of the cavity 111, so that the etching speed also varies depending on the position of the
bottom of the cavity 111. As a result, if the etching gas 72 is less likely to reach the end in the
bottom of the cavity 111 than in the center, for example, the film 120 after processing the cavity
111 has an edge thickness Tc of the center as shown in FIG. 13B. It becomes thinner than the
film thickness Tb of the part.
[0101]
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33
Since the supported portion 122 at the end of the film portion 120 is fixed on the upper surface
of the substrate 110, as shown in FIG. 14, an applied pressure is applied from the hollow portion
111 side and the central portion of the film portion 120 is deformed into a convex shape In that
case, the end is deformed into a concave shape. Therefore, the force applied to the strain sensing
element 200 due to the change in the shape of the film portion 120 is reversed in direction at the
point 120 c. The force Ps exhibits a large value in a narrow range from the boundary point 120d
of the film portion 120 and the substrate 110 to the point 120c. Furthermore, between the point
120d and the point 120c, there is a distribution in the magnitude of the force applied to the
strain sensing element 200 due to the deformation of the film portion 120, and there is a very
narrow region 120e where the force is the largest.
[0102]
The strain sensing element 200 according to the present embodiment has excellent spatial
resolution because the volume is smaller than that of a normal strain sensing element using a
piezo element. Therefore, as shown in FIG. 14, the strain sensing element 200 is disposed at a
pinpoint on the region 120 e between the point 120 c and the point 120 d at which the value of
the force applied to the strain sensing element 200 becomes large on the film portion 120. It is
possible to maximize the performance of the strain sensing element 200 and to increase the
sensitivity of the pressure sensor.
[0103]
As described above, by using a strain sensing element using spin technology, it is possible to
exhibit better performance than using a conventional piezoelectric element as a strain sensing
element. However, the technology of the present invention using aluminum oxide in the film
section that is bent by pressure also exhibits an improvement effect when using a piezoelectric
element. Specifically, when strain is applied as a piezoelectric element, such as PZT or AlN, on the
film portion 120 of the embodiment as shown in FIG. 18, FIG. 22 and FIG. An element in which a
voltage is generated by the polarization effect of electrons can be used. Also in this case, the film
part 120 of the aluminum oxide of the present invention shows an improvement effect.
[0104]
It can be known by theoretical calculation which part becomes the area 120 e on the film part
04-05-2019
34
120. When the theoretical calculation is performed, a structure having a uniform film thickness
is used as a model of the film unit 120. However, in fact, as shown in FIG. 13B, a distribution
exists in the film thickness of the film part 120. At this time, if the actual shape of the film
portion 120 is largely different from the model used for the calculation, the position of the region
120 e on the film portion 120 deviates from the position derived by theoretical calculation. As a
result, the performance of the strain sensing element 200 can not be used to the maximum, and
the pressure sensor of the embodiment can not sufficiently draw out the performance. Therefore,
the shape of the film portion 120 should be close to a model of theoretical calculation, and
should be close to a uniform film thickness. As an example, the ratio (Tc / Te) of the minimum
film thickness Tc to the maximum film thickness Te of the film portion 120 can be, for example,
0.9 or more, preferably 0.95 or more.
[0105]
In order to make the shape of the film portion 120 a shape having a uniform film thickness, it is
necessary to enhance the resistance of the film portion 120 to deep RIE when forming the hollow
portion 111. FIGS. 15A and 15B show a manufacturing process in the case of forming the cavity
111 by etching the substrate 110.
[0106]
When forming the cavity portion 111 by processing the substrate 110 by deep RIE, as shown in
FIG. 15A, since the resistance to deep RIE of the substrate 110 is low, the cavity portion 111 is
different depending on the accessibility of the etching gas. The depth of will vary greatly
depending on the position. FIG. 15A shows, as an example, that the etching gas 72 can easily
reach the center of the cavity 111 than the end of the cavity 111, resulting in faster etching and
a deeper cavity 111. There is. At this time, a difference between the depth of the shallowest
portion of the hollow portion 111 and the depth of the deepest portion is hc1.
[0107]
For example, even if the etching reaches the lower surface of the film portion 120 at the central
portion of the hollow portion 111, the residual portion 111R must also be removed by etching in
order for the vibrating portion 121 to function. However, when etching and removing the
residual portion 111R, as shown in FIG. 15B, the film portion 120 in the vicinity of the central
04-05-2019
35
portion of the hollow portion 111 is partially etched in addition to the residual portion 111R.
That is, the film thickness of the film part 120 is not uniform, and the film thickness difference
hc3 is generated depending on the position. This is not preferable from the viewpoint of the
sensitivity of the pressure sensor as described above.
[0108]
Therefore, in the present embodiment, each of the film portion 120 (the vibrating portion 121
and the supported portion 122) is a single element formed of an oxide (for example, aluminum
oxide (AlOx)) containing aluminum (Al). It is considered to be one film. An oxide containing
aluminum has a high etching rate in relation to silicon or the like which constitutes the substrate
110. When the film portion 120 is formed of a single oxide containing aluminum, the thickness
of the film portion can be 100 nm or more and 2 μm or less.
[0109]
FIG. 16A is a table showing the selectivity to silicon. When etching using RIE is performed on
silicon and sample A under the same conditions, if the etching amount of sample A is 1 / X times
that of silicon, the selectivity of sample A to silicon is X. When the selectivity to silicon is defined
as described above, the selectivity to silicon of silicon oxide film (SiOx) and aluminum oxide
(AlOx) is as shown in FIG. 16A. As shown in FIG. 16A, aluminum oxide exhibits a high selectivity
of 1050 to silicon.
[0110]
For this reason, when the film portion 120 is made of aluminum oxide, even if etching is
performed to remove the residual portion 111R and form the cavity portion 111 until the film
portion 120 is exposed in the region R1, The film thickness is maintained substantially uniformly
above the cavity 111. For this reason, the film thickness of the film part 120 can be made into a
value as a design value, and the sensitivity of pressure sensor 110A can be improved. Also, in the
etching for forming the strain sensing element 200 formed on the film portion 120, the film
portion 120 formed of aluminum oxide has high resistance, so the flatness of the upper surface is
ensured. Thereby, the uniformity of the film thickness of the film part 120 is maintained.
Therefore, it is possible to maximize the performance of the strain sensing element 200 and to
increase the sensitivity of the pressure sensor 110A.
04-05-2019
36
[0111]
As shown in FIGS. 3A to 3D, a plurality of strain sensing elements 200 may be disposed on the
film portion 120 of the pressure sensor 110A. As a result, the improvement of the SNR can be
realized as described above. By thus connecting the plurality of strain sensing elements 200
electrically in series or in parallel to N, an improvement of 20 log NN can be obtained as the SNR.
The sensitivity of the pressure sensor 110A can be increased as compared with the case where
the single strain sensing element 200 is disposed. In order to increase the sensitivity of the
pressure sensor by this method, it is necessary to make the outputs from the individual strain
sensing elements 200 arranged, that is, make the performances uniform. Also in this respect, the
film portion 120 formed of aluminum oxide which can uniformly adjust the film thickness of the
entire film portion 120 has good compatibility with the pressure sensor 110A.
[0112]
FIG. 16B is a schematic diagram for explaining an apparatus for evaluating the sensitivity to the
applied pressure of the vibrating unit 121 of the film unit 120 and a method for evaluating the
apparatus. FIG. 16B shows a schematic configuration of an apparatus for evaluating the
sensitivity of the vibration unit 121. The pressure sensor 110A is fixed on the pressure plate M2,
the pressure plate M2 has a hole M21 having a size similar to that of the vibrating portion 121,
and the pressure is set such that the cavity 111 of the pressure sensor 110A is above the hole
M21. The sensor 110A is fixed. The pressure plate M2 to which the pressure sensor 110A is
fixed is attached to the measurement jig M1. The pressure plate M2 is a lid of the measurement
jig M1, and by attaching the pressure plate M2, a closed cavity M11 is formed. At this time, the
pressure plate M2 is attached to the measurement jig M1 so that the pressure sensor 110A
attached to the pressure plate M2 exists on the surface opposite to the cavity M11.
[0113]
A pressure generator (not shown) is attached to the cavity M11, and an application pressure 80
of a set magnitude can be generated in the cavity M11. The applied pressure 80 is also applied to
the vibrating portion 121 of the pressure sensor 110A connected to the hollow portion M11
through the hole M21. The application of the applied pressure 80 to the vibrating portion 121
changes the shape of the film portion 120. The change in the shape of the film portion 120 is
04-05-2019
37
measured using a laser microscope M3 provided immediately above the pressure sensor 110A.
FIG. 16C is a schematic view of the change of the shape of the film part 120 when the applied
pressure 80 is applied. When the applied pressure 80 is applied to the film portion 120 through
the hollow portion M11, the vibrating portion 121 is bent. At this time, the amount of change D
in the vertical (Z-axis) direction of the film portion 120 from the initial state where the
application pressure 80 of the center of gravity 120P1 of the vibrating portion 121 is not
applied is measured by the laser microscope M3. When the sensitivity to the applied pressure of
the vibrating portion 121 is good, the value of the displacement amount D becomes large even if
the magnitude of the applied pressure 80 is small. Further, when the value of the applied
pressure 80 is changed in a small range, the change of the value of the displacement amount D
also becomes large.
[0114]
The effectiveness of the pressure sensor 110A when an oxide containing aluminum is used as the
film portion 120 will be described with reference to FIGS. 17A to 17D.
[0115]
FIG. 17A is an actual image data showing measurement results by the laser microscope M3 in the
initial state in which no externally applied pressure 80 is applied when aluminum oxide (AlOx)
formed by sputtering is used as the material of the film portion 120. is there.
The residual stress of the film portion 120 before processing of the hollow portion 111 is
adjusted to an appropriate value, and the shape of the vibrating portion 121 is circular. The
diameter of the vibrating portion 121 is 530 μm, and the thickness of the film portion 120 is set
to 500 nm. Note that, for the sake of simplicity, the strain sensing element 200 and an element
without an electrode connected thereto are shown. In FIG. 17A, the inside of the circular portion
corresponds to the vibrating portion 121, and the outside of the circular portion corresponds to
the supported portion 122.
[0116]
FIG. 17B is a diagram showing the height distribution in the vertical direction (Z-axis direction) of
the film part 120 shown in the image data of FIG. 17A by color contrast. The uniform color in
FIG. 17B indicates that the film portion 120 is flat in the initial state. As described later, when the
04-05-2019
38
film portion 120 is largely bent in the initial state, the strain detection element 200 may not be
able to sufficiently exhibit the performance. FIG. 17C shows the section BB ′ of FIG. 17A in the
case where an application pressure 80 of −10 kPa, −5 kPa, −1 kPa, −0.5 kPa, 0 kPa, 0.5 kPa,
1.5 kPa, and 10 kPa is applied to the membrane part 120. The result of having measured the
change of shape with laser microscope M3 is shown. It can be seen that the shapes of the left and
right films are equal at the boundary of the center of gravity 120P1 of the film portion 120, and
the force applied to the strain sensing element 200 disposed at the end of the vibrating portion
121 is equal when the vibrating portion 121 is deformed.
[0117]
FIG. 17D is a graph in which in the case of FIG. 17C, the horizontal axis represents the applied
pressure 80, and the vertical axis represents the displacement amount D of the center of gravity
120P1 of the film portion 120. From this graph, the displacement amount D of the center of
gravity 120P1 of the vibrating portion 121 shows a sharp change in a region where the applied
pressure 80 from the outside is small. That is, it can be seen that the film portion 120 responds
to changes in applied pressure with high sensitivity. A displacement inclination (μm / kPa) as a
change in displacement amount D per unit applied pressure is defined as an index of the
steepness of the change in displacement amount D. The film part 120 shown to FIG. 17A has a
displacement inclination of 3.0 micrometers / kPa in the range of applied pressure -0.5kPa0.5kPa. When the device of the present invention is used as an acoustic sensor or a microphone,
the pressure range to be used is a smaller range, and in such pressure range, it is possible to
detect a weak sound with high sensitivity, with a larger displacement inclination. Become.
[0118]
From the measurement results shown in FIGS. 17C and 17D, when an oxide containing aluminum
is used as the film portion 120, the deflection in the initial state is small, and the shape of the
film when the deflection occurs is symmetrical, against the applied pressure. It can be seen that it
becomes possible to create a pressure sensor 110A having a membrane section that responds
with high sensitivity.
[0119]
Second Embodiment Next, a pressure sensor according to a second embodiment will be described
with reference to FIG.
04-05-2019
39
The pressure sensor according to the second embodiment is different from the first embodiment
in the configuration of the film unit 120. The other configuration is the same as that of the first
embodiment. In FIG. 18, the same components as those of the first embodiment are denoted by
the same reference numerals, and thus the detailed description thereof will be omitted below.
[0120]
FIG. 18 is a schematic cross-sectional view of the A-A ′ cross section of FIG. As shown in FIG.
18, the film unit 120 includes a first film 131 located on the strain sensing element 200 side, a
second film 133 located on the substrate 110 side, and an intermediate film between the first
film 131 and the second film 133. It is formed by 132 three-layer structure. As described later,
by adopting such a three-layer structure, it is possible to provide a flat film portion 120 in which
no deflection occurs in an initial state in which no external applied pressure is applied. In a more
preferable embodiment, the difference between the film thickness of the first film 131 and the
film thickness of the second film 133 is set to a predetermined value or less from the viewpoint
of suppression of residual stress.
[0121]
Each of the first film 131 and the second film 133 is formed of an oxide containing aluminum
(Al). In the first embodiment, the entire film portion 120 is formed of an oxide containing
aluminum, but in the second embodiment, only the upper surface and the lower surface of the
film portion 120 are formed of an oxide containing aluminum. Be done. Since the first film 131
(upper surface of the film portion 120) and the second film 133 (lower surface of the film
portion 120) are made of an oxide containing aluminum, the pressure sensor 110A of the second
embodiment is the same as described above. Similar to the effect of the first embodiment, the
uniformity of the film thickness of the film portion 120 can be secured, and the accuracy of the
pressure sensor 110A can be improved. Further, in the case of the second embodiment, by
selecting the material of the intermediate film 132, physical property values such as Young's
modulus and Poisson's ratio of the film portion 120 can be controlled to values preferable for the
pressure sensor 110A. Note that the thickness of each of the first film 131 and the second film
133 can be 10 μm to 300 μm, and more preferably 20 nm to 200 nm. In this case, preferably,
it can be 30 nm or more and 150 nm or less.
[0122]
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40
The intermediate film 132 can be formed of at least one material selected from the group
consisting of oxides containing silicon and oxides containing silicon and nitrides containing
silicon. Besides, as a material of the intermediate film 132, an organic material such as a polymer
material may be used. Examples of the polymer material include the following. For example,
acrylonitrile bradiene styrene, cycloolefin polymer, ethylene propylene having elasticity,
polyamide, polyamide-imide, polybenzyl imidazole, polybutylene terephthalate, polycarbonate,
polyethylene, polyethylene ether ketone, polyethylimide, polyethylene imine, polyethylene
naphthalene, polyester , Polysulfone, polyethylene terephthalate, phenol formaldehyde,
polyimide, polymethyl methacrylate, polymethyl pentene, polyoxymethylene, polypropylene, mphenyl ether, poly p-phenyl sulfide, p-amide, polystyrene, polysulfone, polyvinyl chloride,
polytetrafluoroethylene Ethene, perfluoroalkoxy, fluorinated ethylene Lenpropylene,
polytetrafluoroethylene, polyethylenetetrafluoroethylene, polyethylenechlorotrifluoroethylene,
polyvinylidene fluoride, melamine formaldehyde, a liquid crystalline polymer, or urine
formaldehyde can be used. The film thickness of the intermediate film 132 can be 100 nm or
more and 1 μm or less. In this case, preferably, it can be 150 nm or more and 800 nm or less.
[0123]
A buffer film or the like (not shown) may be interposed between the intermediate film 132 and
the first film 1231 or the second film 133. Further, the intermediate film 132 may be a single
layer film or a film having a laminated structure.
[0124]
The entire thickness t1 of the film portion 120 can be, for example, 50 nanometers (nm) or more
and 3 micrometers (μm) or less. In this case, preferably, the thickness can be 300 nm or more
and 1.5 μm or less.
[0125]
FIG. 19 shows the thicknesses h1, h2 and h3 of the first film 131, the intermediate film 132 and
the second film 133 constituting the film unit 120, and the residual stress .sigma.1 of the first
film 131, the intermediate film 132 and the second film 133. , Σ 2 and σ 3 are schematic views.
04-05-2019
41
Although FIG. 19 shows the state after the cavity portion 111 is formed for the sake of simplicity,
the residual stresses σ 1, σ 2 and σ 3 respectively indicate the first film 131, the intermediate
film 132 and the second film before the cavity portion 111 is formed. Film 133 is a residual
stress occurring in the film. In order to apply a large strain to the strain sensing element 200
with respect to the pressure from the outside to increase the sensitivity of the pressure sensor
110A, it is desirable that the value of the residual stress σ of the film portion 120 be close to 0
MPa. The average residual stress σ ave of the film portion 120 having a laminated structure is
calculated by the following equation using the film thicknesses h1 to h3 and residual stresses
σ1 to σ3 of the first film 131, the intermediate film 132, and the second film 133.
[0126]
[Equation 1] σave = (h1 * σ1 + h2 * σ2 + h3 * σ3) / (h1 + h2 + h3)
[0127]
In the case of depositing the first film 131 and the second film 133 by depositing an oxide
containing aluminum by sputtering, the residual stresses σ1 and σ3 of the first film 131 and
the second film 133 are controlled by adjusting the pressure of the sputtering gas. Can be
controlled by
At this time, the first film 131 and the second film 133 are deposited as an amorphous aluminum
oxide. The first film 131 is etched by milling for processing the strain sensing element 200
located above it, while the second film 133 is etched by the deep RIE method when the hollow
portion 111 is processed. . If the film thickness h1 of the first film 131 and the film thickness h3
of the second film 133 change due to etching, the average residual stress of the film portion 120
can be understood from the equation [Equation 1]. The value σ ave changes.
[0128]
However, since the first film 131 and the second film 133 formed of an oxide containing
aluminum (Al) have high resistance to milling and RIE, the film thickness does not change before
and after the manufacturing process. As a result, by adopting a structure in which the
intermediate film 132 is sandwiched between the first film 131 and the second film 133 as
shown in FIG. 13, the average residual stress value σave of the film portion 120 can be easily
controlled.
04-05-2019
42
[0129]
Hereinafter, the reason why the deflection of the film portion 120 can be suppressed in the initial
state by the three-layer structure as described above will be described with reference to FIG. In
the following description with reference to FIG. 20, the value of residual stress σ is 0 MPa, and
the residual stress σ when the residual stress in tension is generated in the film portion 120 is a
positive value. The residual stress σ when the compressive residual stress occurs is expressed as
a negative value. FIG. 20 shows the shape of the film portion 120 in the initial state when no
pressure is applied to the film portion 120 from the outside.
[0130]
If there is a distribution of residual stress along the Z-axis direction (the normal direction of the
film portion 120) in the film portion 120 before the processing / formation of the hollow portion
111, the film portion 120 A moment is generated which acts in the direction of increasing the
residual stress σ.
[0131]
First, as shown in FIG. 20A, the difference between the thickness h1 of the first film 131 and the
thickness h3 of the second film 133 is large, and the Z-axis direction (from the cavity 111 side to
the strain sensing element 200 side) Consider the case where a distribution occurs such that the
residual stress of the film portion 120 increases along the direction
In this case, as shown in FIG. 20A, an upward moment M1 is generated in the film portion 120 in
the Z-axis direction.
[0132]
FIG. 20A shows, as an example, the case where h1 >> h3 and σ1> σ2. Further, since h1 >> h3,
there is no contribution from the residual stress σ3. Since the film portion 120 has the moment
M1, the film portion 120 has a large convex shape of the deflection 65a in the initial state. As a
result, a large compression force Ps is applied to the strain sensing element 200.
04-05-2019
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[0133]
Next, as shown in FIG. 20B, the difference in thickness between the film thickness h1 of the first
film 131 and the film thickness h3 of the second film 133 is large, and the Z-axis direction (from
the cavity 111 side to the strain sensing element 200 A case is considered where a distribution is
generated such that the residual stress of the film portion 120 is reduced along the direction
(side direction). In this case, as shown in FIG. 15B, a downward moment M2 is generated in the
film portion 120 in the Z-axis direction. FIG. 15B shows the case where h1 >> h3 and σ1 <σ2 as
an example. Further, since h1 >> h3, there is no contribution from the residual stress σ3. Since
the film portion 120 has a downward moment M2, the film portion 120 has a large concave
shape with a deflection 65b in the initial state. Therefore, a large tensile force Pl is applied to the
strain sensing element 200.
[0134]
When large stress Ps and Pl are applied to the strain sensing element 200 from the initial state,
the magnetostrictive effect is obtained even when the value of the residual stress σ of the film
portion 120 is small and the sensitivity of the film portion 120 to external pressure is good. In
some cases, the change in the magnetization of the magnetic layer does not occur sufficiently,
and the sensitivity of the pressure sensor 110A does not increase.
[0135]
Next, referring to FIG. 20C, the difference between the film thickness h1 of the first film 131 and
the film thickness h3 of the second film 133 is small, and proceeds from the central film 132 of
the film unit 120 toward the cavity 111 side. A case is considered where the residual stress σ
increases and the residual stress σ increases from the center film 132 of the film portion 120
toward the strain sensing element 200.
In this case, the moment M 3 and the moment M 4 resulting from the residual stress σ 1 of the
first film 131 and the residual stress σ 2 of the central film 132 and the residual stress σ 3 of
the second film 133 and the residual stress σ 2 of the central film 132 are Occurs on FIG. 20C
shows, as an example, the case where σ1> σ2 and σ3> σ2. When σ 1 <σ 2 and σ 3 <σ 2,
the directions of the moment M 3 and the moment M 4 are opposite to each other. Since the
moments M3 and M4 are generated in the direction in which the moments M3 and M4 cancel
04-05-2019
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each other, deflection of the film portion 120 is suppressed in the initial state. Therefore, the
force applied to the strain sensing element 200 in the initial state is small.
[0136]
Some strain sensing elements 200 can obtain the highest sensitivity when no tensile or
compressive force is applied in the initial state where no external pressure is applied, but a slight
tensile or compressive force is applied. Some have the highest sensitivity when This depends on
the thickness and material of the film constituting the strain sensing element 200.
[0137]
As a method of applying a minute force to the strain sensing element 200 in the initial state,
there is a method of causing the film portion 120 to have a minute deflection in the initial state.
When the film portion 120 has a three-layer structure substantially symmetrical in the Z-axis
direction as shown in FIG. 18, the magnitudes of the moments M3 and M4 are finely adjusted by
adjusting the magnitudes of the film thicknesses h1, h2 and h3. As a result, it is possible to
control the magnitude of deflection in the initial state of the film portion 120 with high accuracy.
[0138]
The pressure sensor of the embodiment performs annealing to fix the magnetization of the
magnetic layer in the manufacturing process. When the thermal expansion coefficients are
different, thermal stress is generated at the interface between the first film 131 and the
intermediate film 132 and at the interface between the intermediate film 132 and the second
film 133. The influence of the moment generated from these thermal stresses on the initial shape
of the film portion 120 can also be alleviated by providing the film portion 120 with symmetry in
the Z-axis direction as shown in FIG.
[0139]
Further, as shown in FIG. 21A, at the interface between the first film 131 and the intermediate
04-05-2019
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film 132 and at the interface between the intermediate film 132 and the second film 133, the
composition of the film portion 120 is moved by the movement of the elements constituting the
film portion 120. The third film 134 and the fourth film 135 may be newly formed in the
deformed portion. The value of residual stress generated in the third film 134 or the fourth film
135 may be different from that of the first film 131 or the second film 133. The influence on the
initial shape of the film portion 120 due to the moment generated due to the residual stress of
the third film 134 and the fourth film 135 is also made to give symmetry to the film portion 120
in the Z-axis direction as shown in FIG. Can be relaxed.
[0140]
(Effects of the Second Embodiment) As described above, in the pressure sensor 110A of the
second embodiment, the upper surface and the lower surface of the film portion 120 are made of
an oxide containing aluminum. Therefore, as in the effect of the first embodiment described
above, the uniformity of the film thickness of the film unit 120 can be secured, and the sensitivity
of the pressure sensor 110A can be improved. That is, the second film 133 functions as a stopper
film in the etching for forming the hollow portion 111, and the first film 131 functions as a
stopper film in the etching for patterning the strain sensing element 200.
[0141]
In addition, the pressure sensor 110A of the second embodiment can control physical property
values such as residual stress of the film unit 120 by adopting the above-described three-layer
structure for the film unit 120, and in an initial state The deflection of the membrane portion
120 can be suppressed or adjusted, whereby the sensitivity of the pressure sensor can be
improved.
[0142]
In addition, it is described with reference to FIGS. 21B to 21E that the film unit 120 including the
first film 131, the intermediate film 132, and the second film 133 as in the second embodiment
is effective for the pressure sensor 110A.
The evaluation device and evaluation method shown in FIG. 16B are used to evaluate the film
unit 120.
04-05-2019
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[0143]
FIG. 21B is from the outside in the case of using AlOx sputtered as the material of the first film
131 and the second film 133, and using a SiNx film deposited by CVD (Chemical Vapor
Deposition) as the material of the intermediate film 132. It is actual image data which shows the
measurement result by the laser microscope M3 in the initial state to which the pressure
application pressure is not added. The residual stress of the film before processing of the hollow
portion 111 is adjusted to an appropriate value, and the shape of the vibrating portion 121 is
circular. The diameter of the vibrating portion 121 is 530 μm, the thickness of the first film 131
is 100 nm, the thickness 133 of the second film is 50 nm, and the thickness of the intermediate
film 132 is 550 nm. Further, the strain sensing element 200 and an electrode connected to the
strain sensing element 200 are not disposed. In FIG. 21B, the inside of the circular portion
corresponds to the vibrating portion 121, and the outside of the circular portion corresponds to
the supported portion 122.
[0144]
FIG. 21C is a diagram showing the height distribution in the vertical direction (Z-axis direction) of
the film portion 120 shown in the image data of FIG. 21B by color contrast. The uniform color in
FIG. 21C indicates that the film portion 120 is flat in the initial state. As described above, when
the film portion 120 is largely bent in the initial state, the strain sensing element 200 may not be
able to sufficiently exhibit its performance.
[0145]
FIG. 21D is a diagram in the case where an application pressure of −10 kPa, −5 kPa, −1 kPa,
−0.5 kPa, −0.2 kPa, 0 kPa, 0.2 kPa, 0.5 kPa, 1 kPa, 5 kPa, and 10 kPa is applied to the
membrane part 120. The result of having measured the change of the shape of the BB 'section of
21B with laser microscope M3 is shown. It can be seen that the shapes of the left and right films
are equal at the boundary of the center of gravity 120P1 of the film portion 120, and the force
applied to the strain sensing element 200 disposed at the end of the vibrating portion 121 is
equal when the vibrating portion 120 is deformed.
[0146]
04-05-2019
47
FIG. 21E is a graph in which in the case of FIG. 21D, the horizontal axis represents the applied
pressure 80, and the vertical axis represents the displacement amount D of the center of gravity
120P1 of the film portion 120. From this graph, the displacement amount D of the center of
gravity 120P1 of the vibrating portion 121 shows a sharp change in a region where the external
applied pressure 80 is small. That is, it can be seen that the film portion 120 responds to
changes in applied pressure with high sensitivity. The film part 120 shown to FIG. 21B has a
displacement inclination of 3.6 micrometers / kPa in the range of applied pressure -0.2 kPa-0.2
kPa.
[0147]
According to the measurement results shown in FIGS. 21D and 21E, a SiNx film formed by CVD
as the material of the intermediate film 132 is used as the film portion 120 by using AlOx
sputtered as the material of the first film 131 and the second film 133. When used, it can be seen
that the pressure sensor 110A having a thin film portion which has a small deflection in the
initial state, a symmetrical shape of the film when the deflection occurs, and a sensitive response
to the applied pressure can be made. .
[0148]
Third Embodiment Next, a pressure sensor according to a third embodiment will be described
with reference to FIG.
The pressure sensor according to the third embodiment is different from the first embodiment in
the configuration of the membrane unit 120. The other configuration is the same as that of the
first embodiment. In FIG. 22, the same components as those of the first embodiment are denoted
by the same reference numerals, and the detailed description thereof will be omitted below.
[0149]
FIG. 22 is a schematic cross-sectional view of the A-A ′ cross section of FIG. As shown in FIG.
22, the film unit 120 is formed by a two-layer structure of a film 133 disposed on the side of the
substrate 110 and a film 132 disposed above the film 133. The film 133 is made of an oxide
containing aluminum as in the film 133 of the second embodiment, and the film 132 is made of
04-05-2019
48
the same material as the intermediate film 132 of the second embodiment. That is, the film unit
120 of the third embodiment has a configuration in which the first film 131 is removed from the
film unit 120 of the second embodiment. In other words, in the film unit 120 of the third
embodiment, only the first surface on the side of the substrate 110 as the support unit is made of
an oxide containing aluminum. Furthermore, in other words, the film unit 120 of the third
embodiment includes a first film containing an oxide containing aluminum and a third film, and
the third film is between the first film and the strain sensing element. To position. Note that the
film thickness of the film 133 can be 10 μm to 300 μm, more preferably 20 nm to 200 nm.
[0150]
(Effects of the Third Embodiment) As described above, in the pressure sensor 110A of the third
embodiment, the lower surface (film 133) of the film portion 120 is made of an oxide containing
aluminum. There is no oxide film containing aluminum on the upper surface of the film portion
120, so the flatness is slightly lost on the upper surface of the film portion 120, but on the lower
surface of the film portion 120, the film 133 forms a cavity 111. Can function as a stopper film
in etching. For this reason, the uniformity of the film thickness of the film part 120 can be
ensured, and the same effect as that of the first embodiment can be obtained.
[0151]
Fourth Embodiment A pressure sensor according to a fourth embodiment will now be described
with reference to FIG. The pressure sensor according to the fourth embodiment is different from
the above-described embodiment in the configuration of the membrane unit 120. The other
configuration is the same as that of the above-described embodiment. In FIG. 22, since the same
reference numerals are given to the above-described embodiment and the above-described
embodiment, the detailed description thereof will be omitted below.
[0152]
FIG. 23 is a schematic cross-sectional view of the A-A ′ cross section of FIG. As shown in FIG.
23, the film unit 120 is formed by a two-layer structure of a film 131 in which the strain sensing
element 200 is disposed, and a film 132 disposed below the film 131. The film 131 is made of an
oxide containing aluminum as in the film 131 of the second embodiment, and the film 132 is
made of the same material as the intermediate film 132 of the second embodiment. That is, the
04-05-2019
49
film unit 120 of the fourth embodiment has a configuration in which the second film 133 is
removed from the film unit 120 of the second embodiment. In other words, the film portion 120
of the fourth embodiment is made of an oxide containing only the second surface on the strain
sensing element 200 side. Furthermore, in other words, the film unit 120 of the fourth
embodiment includes a second film containing an oxide containing aluminum and a third film,
and the second film is a combination of the third film and the strain sensing element. Located in
between. Note that the film thickness of the film 131 can be 10 μm to 300 μm, and more
preferably 20 nm to 200 nm.
[0153]
(Effects of the Fourth Embodiment) As described above, in the pressure sensor 110A of the
fourth embodiment, the top surface (film 131) of the film portion 120 is made of an oxide
containing aluminum. Since there is no film of an oxide containing aluminum on the lower
surface of the film portion 120, the flatness is slightly lost on the lower surface of the film
portion 120, but the film 131 is used for forming the strain sensing element 200 on the upper
surface of the film portion 120. It can function as a stopper film in the etching for the purpose.
For this reason, the uniformity of the film thickness of the film part 120 can be ensured, and the
same effect as that of the first embodiment can be obtained.
[0154]
FIG. 24A shows an example of the design of the pressure sensor 110A according to the first to
fourth embodiments. FIG. 24A is an example in which a circular shape is adopted for the shape of
the vibrating portion 121, and the diameter is designed to be 530 μm. The length of one side of
the strain sensing element 200 is 10 μm, and a total of 20 or more strain sensing elements are
disposed in a total of 20 or more in total, 30 strain sensing elements in the illustrated example,
on one vibrating portion 121. The electrode 124 connected to the strain sensing element 200 is
routed as much as possible over the supported portion 122 so as not to impede the movement of
the vibrating portion 121. The shape of the beam 123 on the vibrating portion 121 can be
changed in shape in accordance with the arrangement method of the strain sensing element 200,
and may be removed.
[0155]
04-05-2019
50
FIG. 24B is an example in which a rectangular shape is adopted as the shape of the vibrating
portion 121, and the long side of the vibrating portion 121 is designed to be 578 μm and the
short side is designed to be 376 μm. The length of one side of the strain sensing element 200 is
10 μm, and 30 pieces in total are arranged in parallel in the vicinity of the two long sides on the
vibrating portion 121. The electrode 124 connected to the strain sensing element 200 is routed
as much as possible over the supported portion 122 so as not to impede the movement of the
vibrating portion 121. The shape of the beam 123 on the vibrating portion 121 can be changed
in shape in accordance with the arrangement method of the strain sensing element 200, and may
be removed. In FIG. 24A and FIG. 24B, the beams 123 are provided on the film portion 120
which is bent by pressure, but the beams 123 may be omitted. The beam 123 is formed on the
film portion 120 with a material different from that of the film portion 120.
[0156]
FIG. 24C is a schematic view of a cross-sectional structure of the pressure sensor 110A in the
case where a single film formed of an oxide containing aluminum as shown in the first
embodiment is used for the film portion 120. The lower electrode 204 and the upper electrode
212 are arranged such that current flows in the Z-axis direction (direction perpendicular to the
film portion 120) to the strain sensing element 200. The lower electrode 204 and a part of the
upper electrode 212 exist on the vibrating portion 121. Therefore, a material capable of reducing
residual stress is used for the lower electrode 204 and the upper electrode 212 so as not to
prevent the movement of the vibrating portion 121.
[0157]
On the other hand, on the supported portion 122, the gold pad 300 is attached to the lower
electrode 204 and the upper electrode 212. The portions around lower electrode 204, upper
electrode 212 and strain sensing element 200 other than lower electrode embedded insulating
film 303, strain sensing element embedded insulating film 302 and upper electrode 212 in
contact with strain sensing element 200 in order to prevent current leakage. It is protected by
the insulating film 301 which surrounds and the insulating film 304. In the case where the oxide
containing aluminum which forms the film portion 120 exhibits an insulating property, the same
material as the film portion 120 can be used for the insulating films 301, 302, 303, and 304.
That is, low residual stress can be achieved also in the insulating films 301, 302, 303, and 304.
In addition, it is also possible to avoid problems such as film peeling that occur due to differences
in materials at the interface between the film portion 120 and the lower electrode embedded
insulating film 303.
04-05-2019
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[0158]
Further, in order to improve the adhesion between the substrate 110 and the film portion 120,
the adhesion film 305 may be provided between the film portion 120 and the substrate 110.
Since the adhesion film 305 is a thin film, it is scraped off in the region of the vibrating portion
121 when the hollow portion 111 is processed. Therefore, the adhesion film 305 does not affect
the mechanical characteristics of the vibrating portion 121. The magnetic body 306 may be
disposed around the strain sensing element 200. As the magnetic body 306, a hard magnetic
body such as CoPt, CoCrPt, FePt or the like is used as a bias layer for applying to the strain
sensing element. This makes it possible to exhibit stable characteristics as a strain sensing
element and to reduce noise. In the preferred embodiment, the initial magnetization direction of
the strain sensing element is set to be approximately 45 degrees with respect to the direction in
which stress is applied. In consideration of the angle deviation and the like, setting to 30 to 60
degrees is an example of a realistic design.
[0159]
FIG. 24D is a schematic view of a cross-sectional structure of the pressure sensor 110A in the
case where the configuration of the film unit 120 as shown in the second embodiment is
adopted. The lower electrode 204 and the upper electrode 212 are arranged such that current
flows in the Z-axis direction (direction perpendicular to the film portion 120) to the strain
sensing element 200. The lower electrode 204 and a part of the upper electrode 212 exist on the
vibrating portion 121. Therefore, a material capable of reducing residual stress is used for the
lower electrode 204 and the upper electrode 212 so as not to prevent the movement of the
vibrating portion 121. On the supported portion 122, the gold pad 300 is attached to the lower
electrode 204 and the upper electrode 212. In order to prevent current leakage, the lower
electrode 204, the upper electrode 212, and the strain sensing element 200 are surrounded by
portions other than the lower electrode embedded insulating film 303, the strain sensing element
embedded insulating film 302, and the upper electrode 212 in contact with the strain sensing
element 200. It is protected by the surrounding insulating film 301 and the insulating film 304.
[0160]
In the case where the oxide containing aluminum which forms the first film 131 exhibits
04-05-2019
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insulating properties, the same materials as the first film 131 can be used for the insulating films
301, 302, 303, and 304. As a result, at the interface between the first film 131 and the lower
electrode embedded insulating film 303, it is also possible to avoid problems such as film peeling
that occur due to differences in materials. In order to improve the adhesion between the
substrate 110 and the film portion 120, the adhesion film 305 may be provided between the film
portion 120 and the substrate 110. Since the adhesion film 305 is a thin film, it is scraped off in
the region of the vibrating portion 121 when the hollow portion 111 is processed. Therefore, the
adhesion film 305 does not affect the mechanical characteristics of the vibrating portion 121.
The magnetic body 306 may be disposed around the strain sensing element 200. As the
magnetic body 306, a hard magnetic body such as CoPt, CoCrPt, FePt or the like is used as a bias
layer for applying to the strain sensing element. This makes it possible to exhibit stable
characteristics as a strain sensing element and to reduce noise. In the preferred embodiment, the
initial magnetization direction of the strain sensing element is set to be approximately 45
degrees with respect to the direction in which stress is applied. In consideration of the angle
deviation and the like, setting to 30 to 60 degrees is an example of a realistic design. An additive
element may be added to the above hard magnetic material.
[0161]
[Fifth Embodiment] Next, the fifth embodiment will be described with reference to FIG. FIG. 25 is
a schematic cross-sectional view showing the configuration of the microphone 150 according to
the present embodiment. The pressure sensor 110A on which the strain sensing element 200
according to the first to fourth embodiments is mounted can be mounted on, for example, a
microphone.
[0162]
The microphone 150 according to the present embodiment includes a printed circuit board 151
on which the pressure sensor 110A is mounted, an electronic circuit 152 on which the printed
circuit board 151 is mounted, and a cover 153 covering the pressure sensor 110A and the
electronic circuit 152 together with the printed circuit board 151. Prepare. The pressure sensor
110A is a pressure sensor mounted with the strain sensing element 200 according to the first to
third embodiments.
[0163]
04-05-2019
53
The cover 153 is provided with an acoustic hole 154 from which a sound wave 155 is incident.
When the sound wave 155 enters into the cover 153, the sound wave 155 is detected by the
pressure sensor 110A. The electronic circuit 152 applies a current to, for example, a strain
sensing element mounted on the pressure sensor 110A, and detects a change in resistance value
of the pressure sensor 110A. The electronic circuit 152 may amplify this current value by an
amplifier circuit or the like.
[0164]
Since the pressure sensors equipped with the strain sensing element 200 according to the first to
fourth embodiments have high sensitivity, the microphone 150 equipped with this can detect the
sound wave 155 with high sensitivity.
[0165]
Sixth Embodiment Next, the sixth embodiment will be described with reference to FIGS. 26 and
27. FIG.
FIG. 26 is a schematic view showing a configuration of a blood pressure sensor 160 according to
a sixth embodiment. FIG. 27 is a schematic cross-sectional view of the blood pressure sensor 160
as viewed from H1-H2. The pressure sensor 110A equipped with the strain sensing element 200
according to the first to fourth embodiments can be mounted on, for example, the blood pressure
sensor 160.
[0166]
As shown in FIG. 26, the blood pressure sensor 160 is attached, for example, on the artery 166
of the human arm 165. Further, as shown in FIG. 27, the blood pressure sensor 160 is equipped
with a pressure sensor 110A equipped with the strain sensing element 200 according to the first
to fourth embodiments, whereby it is possible to measure the blood pressure. .
[0167]
Since the pressure sensor 110A equipped with the strain sensing element 200 according to the
first to fourth embodiments has high sensitivity, the blood pressure sensor 160 equipped with
04-05-2019
54
this can detect blood pressure continuously with high sensitivity. is there.
[0168]
Seventh Embodiment Next, the seventh embodiment will be described with reference to FIG.
FIG. 28 is a schematic circuit diagram showing the configuration of the touch panel 170
according to the seventh embodiment. The touch panel 170 is mounted on at least one of the
inside of a display (not shown) and the outside of the display.
[0169]
The touch panel 170 includes a plurality of pressure sensors 110A arranged in a matrix and a
plurality of first wirings 171 arranged in the Y direction and connected to one end of the
plurality of pressure sensors 110A arranged in the X direction. , And a plurality of second wires
172 connected to the other ends of the plurality of pressure sensors 110A arranged in the Y
direction, a plurality of first wires 171, and a plurality of second wires. And a control unit 173
which controls 172. The pressure sensor 110A is a pressure sensor according to the first to
fourth embodiments.
[0170]
The control unit 173 also controls the first control circuit 174 that controls the first wiring 171,
the second control circuit 175 that controls the second wiring 172, the first control circuit 174,
and the second control. And a third control circuit 176 that controls the circuit 175.
[0171]
For example, the control unit 173 causes the current to flow to the pressure sensor 110A
through the plurality of first wires 171 and the plurality of second wires 172.
Here, when a touch surface (not shown) is pressed, the pressure sensor 110A changes the
resistance value of the strain sensing element according to the pressure. The control unit 173
04-05-2019
55
detects the change in the resistance value to specify the position of the pressure sensor 110A
that has detected the pressure due to the pressure.
[0172]
Since the pressure sensor 110A equipped with the strain sensing element 200 according to the
first to fourth embodiments has high sensitivity, the touch panel 170 equipped with this can
detect pressure by pressing with high sensitivity. Moreover, the pressure sensor 100 is compact,
and it is possible to manufacture the touch panel 170 with high resolution.
[0173]
The touch panel 170 may include a detection element for detecting a touch in addition to the
pressure sensor 110A.
[0174]
[Other Applications] The application of the pressure sensor 110A equipped with the strain
sensing element 200 according to the first to fourth embodiments has been described with
reference to specific examples.
However, the pressure sensor 110A can be applied to various pressure sensor devices such as an
air pressure sensor and a tire air pressure sensor, in addition to the embodiments shown in the
fifth to seventh embodiments.
[0175]
In addition, specific examples of each element such as the strain sensing element 200, the
pressure sensor 110A, the microphone 150, the film portion included in the blood pressure
sensor 160, and the touch panel 170, the strain sensing element, the first magnetic layer, the
second magnetic layer, and the intermediate layer The same configuration can be similarly
implemented by those skilled in the art by appropriately selecting from the known range, and
included in the scope of the present invention as long as similar effects can be obtained.
[0176]
04-05-2019
56
Moreover, what combined any two or more elements of each specific example in the technically
possible range is also included in the scope of the present invention as long as the gist of the
present invention is included.
[0177]
In addition, all strain sensing elements that can be appropriately designed and implemented by
those skilled in the art based on the strain sensing element, the pressure sensor 110A, the
microphone 150, the blood pressure sensor 160, and the touch panel 170 described above as
the embodiment The pressure sensor 100, the microphone 150, the blood pressure sensor 160,
and the touch panel 170 are also included in the scope of the present invention as long as the
scope of the present invention is included.
[0178]
While certain embodiments of the invention have been described above, these embodiments have
been presented by way of example only, and are not intended to limit the scope of the invention.
These novel embodiments can be implemented in other various forms, and various omissions,
replacements and changes can be made without departing from the scope of the invention.
These embodiments and modifications thereof are included in the scope and the gist of the
invention, and are included in the invention described in the claims and the equivalent scope
thereof.
[0179]
110A: pressure sensor 110: substrate 111: hollow portion 120: membrane portion 121: vibration
portion 122: supported portion 131: first film 132: intermediate film 133 2 membranes, C1, C2
... wiring, P1, PP2 ... pad, 150 ... microphone, 151 ... printed circuit board, 152 ... electronic
circuit, 153 ... cover, 154 ... acoustic hole, 155 ... sound, 160 ... blood pressure sensor, 165 ... arm
, 166: artery, 170: touch panel, 171: first wiring, 172: second wiring, 173: control unit, 174: first
control circuit, 175: second control circuit, 176: third control Circuit 200 strain detection
element 201 first magnetic layer 202 second magnetic layer 203 intermediate layer 204 lower
electrode 205 underlying layer 206 pinning layer 207 Magnetization fixed layer 208 magnetic
coupling layer 209 first magnetization fixed layer 210 magnetization free layer 211 cap layer
212 upper electrode 213 insulating layer 214 hard bias layer 215 protective layer 221 lower
04-05-2019
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pinning layer 222 lower second magnetization fixed layer 223 lower magnetic coupling layer
224 lower first magnetization fixed layer 225 lower intermediate layer 226 magnetization free
layer 227 upper intermediate layer 228 Upper first magnetization fixed layer 229 Upper
magnetic coupling layer 230 Upper second magnetization fixed layer 231 Upper pinning layer
241 First magnetization free layer 242 Second magnetization free layer
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