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DESCRIPTION JP2016015434

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DESCRIPTION JP2016015434
The present invention provides an ultrasonic probe provided with a piezoelectric element having
good adhesion between a diaphragm and platinum and high withstand voltage. An element chip
(17) and a casing for supporting the element chip (17). The element chip (17) includes a
vibrating film (43), a lower electrode (24), and a piezoelectric film (26) formed on the lower
electrode. The lower electrode 24 is stacked on the vibrating film 43 via the adhesion film 24b,
the lower electrode 24 is platinum or an alloy containing platinum, and the adhesion film 24b is
titanium having a film thickness of 80 Å or less. [Selected figure] Figure 4
Ultrasound probe
[0001]
The present invention relates to an ultrasound probe.
[0002]
An ultrasonic diagnostic apparatus for irradiating a living body with ultrasonic waves from an
ultrasonic transducer element chip installed in an ultrasonic probe and analyzing a reflected
wave is widely used.
Piezoelectric elements are often used for ultrasonic transducer element chips. The piezoelectric
element generally has a structure including a piezoelectric thin film made of a polycrystalline
body, and an upper electrode and a lower electrode which are disposed with the piezoelectric
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thin film interposed therebetween.
[0003]
A platinum film is formed directly on SiO 2 as the lower electrode of the piezoelectric thin film.
However, it is a well-known fact that there is a problem in the adhesion between SiO 2 and
platinum in such a configuration. Peeling occurs between silicon oxide and platinum at the time
of heat treatment at the time of formation of the PZT film or thereafter, or at the time of
operation after completion. Patent Document 1 discloses a method for solving the above
problems. According to it, titanium is inserted between platinum and the insulating material in
order to improve the adhesion between the insulating material such as SiO 2 and the platinum.
[0004]
Japanese Examined Patent Publication No. 4-43435
[0005]
In the method described in Patent Document 1, protrusions are formed on the surface of
platinum during the formation of the piezoelectric thin film and the heat treatment thereafter.
The protrusions reduce the withstand voltage of the piezoelectric element. Therefore, there has
been a demand for an ultrasonic probe provided with a piezoelectric element having good
adhesion between a diaphragm and platinum and high withstand voltage.
[0006]
The present invention has been made to solve the above-described problems, and can be realized
as the following modes or application examples.
[0007]
Application Example 1 An ultrasonic probe according to this application example, comprising: an
ultrasonic transducer element chip; and a case for supporting the ultrasonic transducer element
chip, wherein the ultrasonic transducer element chip is A metal film formed on a vibrating film,
and a piezoelectric thin film formed on the metal film, wherein the metal film is laminated on the
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vibrating film via an adhesive film, and the metal film is platinum Or an alloy containing
platinum, and the adhesion film is titanium having a film thickness of 80 Å or less.
[0008]
According to this application example, the housing supports the ultrasonic transducer element
chip in the ultrasonic probe.
The ultrasonic transducer element chip includes a vibrating membrane, and a metal film is
formed on the vibrating membrane.
A piezoelectric thin film is formed on the metal film. The metal film is platinum or an alloy
containing platinum, and the adhesion film is titanium having a film thickness of 80 Å or less.
Thereby, the metal film can improve the adhesion to the vibrating film, and the withstand voltage
of the PZT film can be improved.
[0009]
FIG. 1 is a schematic perspective view of a configuration of an ultrasonic diagnostic apparatus
according to a first embodiment. The tissue side view which shows the structure of an ultrasound
probe. FIG. 2 is a schematic plan view showing the configuration of an element chip. FIG. 2 is a
schematic side sectional view showing the configuration of an element chip. The model top view
which shows a reinforcement board. The principal part model enlarged view which shows a
reinforcement board. The circuit diagram of an apparatus terminal and an ultrasonic probe. The
schematic diagram for demonstrating the manufacturing method of an ultrasonic transducer
element chip | tip. (A) is a model exploded view which shows the structure of a protection jig, (b)
is a model sectional side view which shows the structure of a protection jig. FIG. 2 is a schematic
side sectional view showing the configuration of an element chip having a laminated structure of
a diaphragm. FIG. 2 is a schematic side sectional view showing the configuration of an element
chip having a laminated structure of a diaphragm. FIG. 7 is a schematic view for explaining the
method of manufacturing an ultrasonic transducer element chip according to the second
embodiment. The schematic diagram for demonstrating the manufacturing method of an
ultrasonic transducer element chip | tip. FIG. 10 is a schematic plan view showing the structure
of an element chip according to a third embodiment. (A) is a model top view which shows the
structure of an ultrasonic transducer element, (b) is a principal part model sectional side view
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which shows the structure of an ultrasonic transducer element. FIG. 3 is a schematic plan view
showing the structure of an ultrasonic transducer element. FIG. 7 is a schematic view for
explaining the method of manufacturing a piezoelectric element. FIG. 7 is a schematic view for
explaining the method of manufacturing a piezoelectric element. FIG. 7 is a schematic view for
explaining the method of manufacturing a piezoelectric element. The principal part schematic
cross section which shows the structure of the piezoelectric element in connection with a
modification. The principal part schematic cross section which shows the structure of a
piezoelectric element. FIG. 2 is a main part schematic plan view showing a structure of a
piezoelectric element. FIG. 2 is a main part schematic plan view showing a structure of a
piezoelectric element. FIG. 2 is a main part schematic plan view showing a structure of a
piezoelectric element. FIG. 2 is a main part schematic plan view showing a structure of a
piezoelectric element. (A) is a principal part model top view which shows the structure of a
piezoelectric element, (b) is a principal part model sectional side view which shows the structure
of a piezoelectric element. (A) is a principal part model top view which shows the structure of a
piezoelectric element, (b) is a principal part model sectional side view which shows the structure
of a piezoelectric element. FIG. 7 is a schematic view for explaining the method of manufacturing
a piezoelectric element. FIG. 2 is a main part schematic plan view showing a structure of a
piezoelectric element. FIG. 2 is a main part schematic plan view showing a structure of a
piezoelectric element. (A) is a principal part model top view which shows the structure of a
piezoelectric element, (b) is a principal part model sectional side view which shows the structure
of a piezoelectric element. (A) is a principal part schematic plan view which shows the structure
of a piezoelectric element, (b) and (c) is a principal part schematic cross section which shows the
structure of a piezoelectric element. FIG. 2 is a main part schematic plan view showing a
structure of a piezoelectric element. (A) is a principal part model top view which shows the
structure of a piezoelectric element, (b) is a principal part model sectional side view which shows
the structure of a piezoelectric element. FIG. 2 is a main part schematic plan view showing a
structure of a piezoelectric element.
(A) And (b) is a principal part schematic plan view which shows the structure of a piezoelectric
element. FIG. 2 is a main part schematic plan view showing a structure of a piezoelectric element.
FIG. 2 is a main part schematic plan view showing a structure of a piezoelectric element. (A) is a
principal part schematic plan view which shows the structure of a piezoelectric element, (b) and
(c) is a principal part schematic cross section which shows the structure of a piezoelectric
element. FIG. 2 is a main part schematic plan view showing a structure of a piezoelectric element.
(A) is a principal part model top view which shows the structure of a piezoelectric element, (b) is
a principal part model sectional side view which shows the structure of a piezoelectric element.
(A) And (b) is a principal part schematic sectional side view which shows the structure of a
piezoelectric element. (A) is a principal part model top view which shows the structure of a
piezoelectric element, (b) is a principal part model sectional side view which shows the structure
of a piezoelectric element. (A) is a principal part model top view which shows the structure of a
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piezoelectric element, (b) is a principal part model sectional side view which shows the structure
of a piezoelectric element. (A) is a principal part model top view which shows the structure of a
piezoelectric element, (b) is a principal part model sectional side view which shows the structure
of a piezoelectric element.
[0010]
Hereinafter, an embodiment of the present invention will be described with reference to the
attached drawings. Note that the present embodiment described below does not unduly limit the
contents of the present invention described in the claims, and all of the configurations described
in the present embodiment are used as the means for solving the present invention. It is not
necessarily mandatory. First Embodiment In the present embodiment, a characteristic example of
an ultrasonic diagnostic apparatus will be described according to FIGS.
[0011]
(1) Overall Configuration of Ultrasonic Diagnostic Apparatus FIG. 1 is a schematic perspective
view showing the configuration of the ultrasonic diagnostic apparatus. As shown in FIG. 1, the
ultrasonic diagnostic apparatus 11 includes an apparatus terminal 12 and an ultrasonic probe 13
(probe). The device terminal 12 and the ultrasonic probe 13 are connected to each other by a
cable 14. The device terminal 12 and the ultrasonic probe 13 exchange electrical signals through
the cable 14. A display panel 15 (display device) is incorporated in the device terminal 12. The
screen of the display panel 15 is exposed on the surface of the device terminal 12. At the device
terminal 12, an image is generated based on the ultrasonic waves detected by the ultrasonic
probe 13, as described later. The imaged detection result is displayed on the screen of the display
panel 15.
[0012]
FIG. 2 is a tissue side view showing the configuration of the ultrasonic probe. As shown in FIG. 2,
the ultrasonic probe 13 has a housing 16. An element chip 17 as an ultrasonic transducer
element chip is accommodated in the housing 16. The surface of the element chip 17 can be
exposed on the surface of the housing 16. The element chip 17 outputs an ultrasonic wave from
the surface and receives a reflected wave of the ultrasonic wave. In addition, the ultrasonic probe
13 can include a probe head 13 b that is detachably coupled to the probe body 13 a. At this time,
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the element chip 17 can be incorporated into the housing 16 of the probe head 13b.
[0013]
FIG. 3 is a schematic plan view showing the configuration of the element chip. As shown in FIG.
3, the element chip 17 includes a substrate 21. An element array 22 is formed on the substrate
21. The element array 22 is composed of an array of piezoelectric elements 23 as ultrasonic
transducer elements. The array is formed of a matrix of rows and columns. Each piezoelectric
element 23 includes a piezoelectric element portion. The piezoelectric element portion is
composed of a lower electrode 24 as a metal film, an upper electrode 25 and a piezoelectric film
26 as a piezoelectric thin film. The piezoelectric film 26 is sandwiched between the lower
electrode 24 and the upper electrode 25 for each piezoelectric element 23.
[0014]
The lower electrode 24 has a plurality of first conductors 24a. The first conductors 24a extend
parallel to each other in the row direction of the array. One first conductor 24 a is allocated to
each row of piezoelectric elements 23. One first conductor 24 a is commonly disposed in the
piezoelectric films 26 of the piezoelectric elements 23 arranged in the row direction of the array.
Both ends of the first conductor 24 a are connected to the pair of lead wirings 27 respectively.
The lead wires 27 extend parallel to each other in the column direction of the array. Therefore,
all the first conductors 24a have the same length. Thus, the lower electrode 24 is commonly
connected to the piezoelectric elements 23 of the entire matrix.
[0015]
The upper electrode 25 has a plurality of second conductors 25a. The second conductors 25a
extend parallel to each other in the column direction of the array. One second conductor 25 a is
allocated to each row of piezoelectric elements 23. One second conductor 25a is commonly
disposed in the piezoelectric films 26 of the piezoelectric elements 23 arranged in the column
direction of the array. The energization of the piezoelectric element 23 is switched for each row.
Line scan and sector scan are realized according to such switching of energization. Since the
piezoelectric elements 23 in one row simultaneously output ultrasonic waves, the number of one
columns, that is, the number of rows in the array can be determined according to the output level
of the ultrasonic waves. The number of rows may be set to, for example, about 10 to 15 rows.
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Five lines are drawn, omitted in the figure. The number of columns of the array can be
determined according to the spread of the scan range. The number of columns may be set to 128
or 256, for example. It is omitted in the figure and eight columns are drawn. Alternatively, a
staggered arrangement may be established in the arrangement. In the staggered arrangement,
the piezoelectric elements 23 in the even numbered columns may be shifted by half the row
pitch with respect to the piezoelectric elements 23 in the odd numbered columns. The number of
elements in one of the odd and even columns may be smaller by one than the number of
elements in the other. Furthermore, the roles of the lower electrode 24 and the upper electrode
25 may be switched. That is, while the upper electrode is commonly connected to the
piezoelectric elements 23 of the entire matrix, the lower electrode may be commonly connected
to the piezoelectric elements 23 in each array row.
[0016]
The outline of the substrate 21 has a first side 21 a and a second side 21 b which are separated
by a pair of straight lines 29 which are parallel to each other. A first terminal array 32a of one
line is disposed between the first side 21a and the outline of the element array 22 in the
peripheral area 31 extending between the outline of the element array 22 and the outer edge of
the substrate 21. The second terminal array 32 b of one line is disposed between 21 b and the
contour of the element array 22. The first terminal array 32a can form one line parallel to the
first side 21a. The second terminal array 32b can form one line parallel to the second side 21b.
The first terminal array 32 a includes a pair of lower electrode terminals 33 and a plurality of
upper electrode terminals 34. Similarly, the second terminal array 32 b includes a pair of lower
electrode terminals 35 and a plurality of upper electrode terminals 36. Lower electrode terminals
33 and 35 are connected to both ends of one lead wire 27 respectively. The lead wire 27 and the
lower electrode terminals 33 and 35 may be formed plane-symmetrically in a vertical plane that
bisects the element array 22. The upper electrode terminals 34 and 36 are connected to both
ends of one second conductor 25a. The second conductor 25 a and the upper electrode terminals
34 and 36 may be formed plane-symmetrically in a vertical plane that bisects the element array
22. Here, the outline of the substrate 21 is formed in a rectangular shape. The contour of the
substrate 21 may be square or trapezoidal.
[0017]
The first flexible printed circuit board 37 is connected to the substrate 21 as a first flexible
printed circuit board. The first flexible member 37 covers the first terminal array 32a. At one end
of the first flexible member 37, conductive lines, ie, first signal lines 38 are formed
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corresponding to the lower electrode terminal 33 and the upper electrode terminal 34
respectively. The first signal lines 38 individually face the individual lower electrode terminals 33
and the upper electrode terminals 34 and are joined separately. Similarly, the substrate 21 is
covered with a second flexible printed circuit 41 as a second flexible printed circuit. The second
flexible cable 41 covers the second terminal array 32b. A conductive line, that is, a second signal
line 42 is formed corresponding to the lower electrode terminal 35 and the upper electrode
terminal 36 individually at one end of the second flexible member 41. The second signal lines 42
individually face the individual lower electrode terminals 35 and the upper electrode terminals
36 and are joined separately.
[0018]
FIG. 4 is a schematic side sectional view showing the structure of the element chip. As shown in
FIG. 4, each piezoelectric element 23 has a vibrating film 43. In order to construct the vibrating
film 43, an opening 45 is formed in the base 44 of the substrate 21 for each of the individual
piezoelectric elements 23. The openings 45 are arranged in an array relative to the substrate 44.
A flexible film 46 is formed on one surface of the substrate 44. The flexible film 46 is composed
of a silicon oxide layer 47 (SiO 2) laminated on the surface of the base 44 and an upper surface
layer 48 laminated on the surface of the silicon oxide layer 47. The upper surface layer 48 can
be made of a silicon nitride film or zirconium oxide (ZrO 2). In the present embodiment, silicon
nitride is used for the upper surface layer 48, for example. Even if the upper surface layer 48 is
not provided, the upper surface layer 48 may be omitted when elasticity is obtained in the
vibrating film 43. The flexible membrane 46 is in contact with the opening 45. In this way, a part
of the flexible film 46 functions as the vibrating film 43 corresponding to the contour of the
opening 45. The film thickness of the silicon oxide layer 47 is determined based on the resonant
frequency.
[0019]
The lower electrode 24, the piezoelectric film 26 and the upper electrode 25 are sequentially
stacked on the surface of the vibrating film 43. For the lower electrode 24, for example, a
laminated film of titanium (Ti), iridium (Ir), platinum (Pt) and titanium (Ti), or a film of platinum
can be used. In the present embodiment, for example, a platinum film is used for the lower
electrode 24, and the adhesion film 24 b is provided between the lower electrode 24 and the
upper surface layer 48. A titanium film is used for the adhesion film 24b. Therefore, a stacked
film of the adhesion film 24 b and the lower electrode 24 is disposed on the upper surface layer
48. The lower electrode 24 is platinum or an alloy containing platinum, and the adhesion film 24
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b is titanium having a film thickness of 80 Å or less. Titanium is a metal having good adhesion to
various metals including platinum. Thereby, the lower electrode 24 can improve the adhesion
with the flexible film 46.
[0020]
The piezoelectric film 26 can be formed of, for example, lead zirconate titanate (PZT). The upper
electrode 25 can be made of, for example, iridium (Ir), platinum (Pt), titanium, gold or a film in
which these are combined. In the present embodiment, for example, a laminated film of titanium
and gold is used for the upper electrode 25. Other conductive materials may be used for the
lower electrode 24 and the upper electrode 25, and other piezoelectric materials may be used for
the piezoelectric film 26. Here, the piezoelectric film 26 completely covers the lower electrode 24
under the upper electrode 25. A short circuit can be avoided between the upper electrode 25 and
the lower electrode 24 by the action of the piezoelectric film 26.
[0021]
A protective film 49 is stacked on the surface of the substrate 21. The protective film 49 covers
the entire surface, for example, on the surface of the substrate 21. As a result, the element array
22, the first terminal array 32 a and the second terminal array 32 b, the first flex 37 and the
second flex 41 are covered with the protective film 49. For example, a silicone resin film can be
used for the protective film 49. The protective film 49 protects the structure of the element array
22, the junction of the first terminal array 32 a and the first flex 37, and the junction of the
second terminal array 32 b and the second flex 41.
[0022]
A partition wall 51 is partitioned between the adjacent openings 45. The openings 45 are
separated by the partition wall 51. The wall thickness t of the partition wall 51 corresponds to
the space between the openings 45. The partition wall 51 defines two wall surfaces in a plane
extending parallel to one another. The wall thickness t corresponds to the distance between the
wall surfaces. That is, the wall thickness t can be defined by the length of a perpendicular line
perpendicular to the wall surface and sandwiched between the wall surfaces. The wall height H
of the partition wall 51 corresponds to the depth of the opening 45. The depth of the opening 45
corresponds to the thickness of the substrate 44. Therefore, the wall height H of the partition
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wall 51 can be defined by the length of the wall surface defined in the thickness direction of the
base 44. Since the substrate 44 has a uniform thickness, the partition wall 51 can have a
constant wall height H over the entire length. If the wall thickness t of the partition wall 51 is
reduced, the arrangement density of the vibrating film 43 can be increased, which can contribute
to the miniaturization of the element chip 17. If the wall height H of the partition wall 51 is
larger than the wall thickness t, the bending rigidity of the element chip 17 can be enhanced.
Thus, the distance between the openings 45 is set smaller than the depth of the openings 45.
[0023]
The reinforcing plate 52 (reinforcement member) is fixed to the back surface of the base 44. The
back surface of the base 44 is superimposed on the front surface of the reinforcing plate 52. The
reinforcing plate 52 closes the opening 45 at the back surface of the element chip 17. The
reinforcing plate 52 can comprise a rigid substrate. The reinforcing plate 52 can be formed of,
for example, a silicon substrate. The thickness of the base 44 is set to, for example, about 100
μm, and the thickness of the reinforcing plate 52 is set to, for example, about 100 to 150 μm.
Here, the partition wall 51 is coupled to the reinforcing plate 52. The reinforcing plate 52 is
joined to the individual partition walls 51 in at least one joint area. An adhesive may be used for
bonding.
[0024]
A linear groove 53 (linear groove) is formed on the surface of the reinforcing plate 52. The
grooves 53 divide the surface of the reinforcing plate 52 into a plurality of flat surfaces 54. The
plurality of planes 54 extend in one virtual plane HP. The back surface of the base 44 spreads in
the virtual plane HP. The partition wall 51 is joined to the flat surface 54. The groove 53 is
recessed from the virtual plane HP. The cross-sectional shape of the groove 53 may be
rectangular, triangular, semicircular or the like.
[0025]
FIG. 5 is a schematic plan view showing a reinforcing plate. As shown in FIG. 5, the openings 45
form a row in the first direction D1. The centroids 45b of the contour shape of the openings 45
are arranged at an equal pitch on one straight line 56 in the first direction D1. Since the contour
45a of the openings 45 is represented by copying of one shape, the openings 45 of the same
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shape are repeatedly arranged at a constant pitch. The contour 45a of the opening 45 is defined,
for example, as a square. Specifically, it is formed in a rectangular shape. The long side of the
rectangle is aligned with the first direction D1. Thus, since the opening 45 has a rectangular
outline 45a, the partition wall 51 can have a constant wall thickness t over the entire length. At
this time, the bonding area of the partition wall 51 may be an area including the central position
of the long side. In particular, the bonding area of the partition wall 51 may be an area including
the entire length of the long side. The partition wall 51 can be surface-joined to the reinforcing
plate 52 on the entire surface between the openings 45 over the entire length of the long side.
Furthermore, the bonding area of the partition wall 51 can be disposed at least one place on each
side of the square. The junction area of the partition wall 51 can surround the square without
interruption. The partition wall 51 can be surface-bonded to the reinforcing plate 52 on the
entire surface between the openings 45 over the entire circumference of the square.
[0026]
The grooves 53 are arranged in the first direction D1 parallel to each other at a constant distance
L. The groove 53 extends in a second direction D2 intersecting the first direction D1. Both ends
of the groove 53 open at the end face 57 a and the end face 57 b of the reinforcing plate 52. One
groove 53 sequentially crosses the contour 45 a of the opening 45 in one row (here, one row). At
least one groove 53 is connected to each opening 45. Here, the second direction D2 is orthogonal
to the first direction D1. Therefore, the groove 53 crosses the contour 45 a of the opening 45 in
the direction of the short side of the rectangle.
[0027]
FIG. 6 is a main part schematic enlarged view showing a reinforcing plate. As shown in FIG. 6,
between the flats 54, the groove 53 forms a passage 58a and a passage 58b between the base 44
and the reinforcing plate 52. Thus, the space in the groove 53 communicates with the internal
space of the opening 45. The passages 58 a and 58 b ensure ventilation between the internal
space of the opening 45 and the external space of the substrate 21. In a plan view seen from the
direction orthogonal to the surface of the substrate 21, ie, the thickness direction of the substrate
21, one groove 53 sequentially traverses the contour 45a of the openings 45 in one row (here,
one row). The openings 45 are connected by a passage 58a. Both ends of the groove 53 open at
the end face 57 a and the end face 57 b of the reinforcing plate 52. Thus, the passage 58b is
opened from the opening 45 of the row end to the outside of the outline of the substrate 21.
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[0028]
The distance L between the grooves 53 is set smaller than the opening width S of the opening
45. The opening width S is defined by the largest length of the line segments crossing the
opening 45 in the alignment direction of the grooves 53, ie, the first direction D1. In other words,
the opening width S corresponds to the distance between the parallel lines 59 circumscribing the
contour 45 a of the opening 45. Parallel lines 59 circumscribing the contour 45 a of the opening
45 are identified for each opening 45. The parallel lines 59 extend in the second direction D2. If
the opening widths S are different from each other for each opening 45, the grooves 53 may be
arranged at an interval L smaller than the minimum value of the opening width S. Here, the
distance L between the grooves 53 is set to one-third or more of the opening width S of the
opening 45 and smaller than one-half.
[0029]
(2) Circuit Configuration of Ultrasonic Diagnostic Apparatus FIG. 7 is a circuit diagram of an
apparatus terminal and an ultrasonic probe. As shown in FIG. 7, the ultrasonic probe 13 is
provided with an integrated circuit chip 55 connected to the element chip 17. The integrated
circuit chip 55 comprises a multiplexer 61 and a transceiver circuit 62. The multiplexer 61
includes a port group 61 a on the element chip 17 side and a port group 61 b on the
transmitting and receiving circuit 62 side. The first signal line 38 and the second signal line 42
are connected to the port group 61 a on the element chip 17 side via the first wiring 60. Thus,
the port group 61a is connected to the element array 22. Here, a specified number of signal lines
63 in the integrated circuit chip 55 are connected to the port group 61b on the transmission /
reception circuit 62 side. The specified number corresponds to the number of rows of
piezoelectric elements 23 simultaneously output in scanning. The multiplexer 61 manages the
interconnection between the port on the cable 14 side and the port on the element chip 17 side.
[0030]
The transmission / reception circuit 62 is provided with a specified number of changeover
switches 64. Each changeover switch 64 is connected to the signal line 63, respectively. The
transmission / reception circuit 62 includes a transmission path 65 and a reception path 66 for
each of the changeover switches 64. The transmission path 65 and the reception path 66 are
connected in parallel to the changeover switch 64. The changeover switch 64 selectively
connects the transmission path 65 or the reception path 66 to the multiplexer 61. A pulser 67 is
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incorporated in the transmission path 65. The pulser 67 outputs a pulse signal at a frequency
corresponding to the resonant frequency of the vibrating membrane 43. In the reception path
66, an amplifier 68, a low pass filter 69 (LPF) and an analog-to-digital converter 71 (ADC) are
incorporated. The detection signals of the individual piezoelectric elements 23 are amplified and
converted into digital signals.
[0031]
The transmission / reception circuit 62 includes a drive / reception circuit 72. The transmission
path 65 and the reception path 66 are connected to the drive / reception circuit 72. The drive /
reception circuit 72 simultaneously controls the pulser 67 in accordance with the form of scan.
The drive / reception circuit 72 receives the digital signal of the detection signal according to the
form of scan. The drive / reception circuit 72 is connected to the multiplexer 61 by a control line
73. The multiplexer 61 carries out the management of interconnection based on the control
signal supplied from the drive / reception circuit 72.
[0032]
A processing circuit 74 is incorporated in the device terminal 12. The processing circuit 74 can
include, for example, a central processing unit (CPU) and a memory. The entire operation of the
ultrasonic diagnostic apparatus 11 is controlled in accordance with the processing of the
processing circuit 74. The processing circuit 74 controls the drive / reception circuit 72 in
accordance with an instruction input from the user. The processing circuit 74 generates an image
in accordance with the detection signal of the piezoelectric element 23. The image is identified by
the drawing data.
[0033]
A drawing circuit 75 is incorporated in the device terminal 12. The drawing circuit 75 is
connected to the processing circuit 74. The display panel 15 is connected to the drawing circuit
75. The drawing circuit 75 generates a drive signal in accordance with the drawing data
generated by the processing circuit 74. The drive signal is sent to the display panel 15. As a
result, an image is displayed on the display panel 15.
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[0034]
(3) Operation of Ultrasonic Diagnostic Apparatus Next, the operation of the ultrasonic diagnostic
apparatus 11 will be briefly described. The processing circuit 74 instructs the drive / reception
circuit 72 to transmit and receive ultrasonic waves. The drive / reception circuit 72 supplies a
control signal to the multiplexer 61 and supplies a drive signal to each pulser 67. The pulser 67
outputs a pulse signal in response to the supply of the drive signal. The multiplexer 61 connects
the ports of the port group 61a to the ports of the port group 61b according to the instruction of
the control signal. A pulse signal is supplied to the piezoelectric element 23 for each column
through the lower electrode terminal 33, the lower electrode terminal 35, the upper electrode
terminal 34, and the upper electrode terminal 36 in accordance with the selection of the port.
The vibrating film 43 vibrates in response to the supply of the pulse signal. As a result, desired
ultrasonic waves are emitted toward the object (for example, the inside of the human body).
[0035]
After transmission of the ultrasonic waves, the changeover switch 64 is switched. The
multiplexer 61 maintains the connection of the ports. The changeover switch 64 establishes the
connection of the reception path 66 and the signal line 63 instead of the connection of the
transmission path 65 and the signal line 63. The reflected wave of the ultrasonic wave vibrates
the vibrating film 43. As a result, a detection signal is output from the piezoelectric element 23.
The detection signal is converted into a digital signal and sent to the drive / reception circuit 72.
[0036]
Transmission and reception of ultrasonic waves are repeated. At the time of repetition, the
multiplexer 61 changes the connection of ports. As a result, line scan and sector scan are
realized. When the scan is complete, the processing circuit 74 forms an image based on the
digital signal of the detection signal. The formed image is displayed on the screen of the display
panel 15.
[0037]
(4) Method of Manufacturing Ultrasonic Transducer Element Chip FIG. 8 is a schematic view for
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explaining a method of manufacturing an ultrasonic transducer element chip. As shown in FIG.
8A, the substrate 44 is thermally oxidized at 1200 ° C. with single crystal silicon of plane
orientation (110) to form a silicon oxide layer 47 with a thickness of 5000 Å on both surfaces of
the substrate 44. Then, the upper surface layer 48 is formed on one side of the base 44. The
upper surface layer 48 is formed, for example, by forming silicon nitride to a thickness of 1 μm
by PECVD (plasma chemical vapor deposition), and performing heat treatment at 800 ° C. in a
nitrogen atmosphere. Further, a photoresist is formed on both sides of the base 44, an opening is
provided on the surface opposite to the side on which the upper surface layer 48 is provided, and
the silicon oxide layer 47 is patterned with an aqueous solution of hydrofluoric acid and
ammonium fluoride Form 77. At this time, the depth direction of the opening 77, that is, the
direction perpendicular to the paper surface is set to the <1-12> or <-112> direction.
[0038]
As shown in FIG. 8B, the adhesion film 24 b and the lower electrode 24 are formed on the upper
surface layer 48. Titanium is formed to a thickness of 50 Å and platinum to a thickness of 2000
Å by sputtering, and patterning is performed with an aqueous solution of aqua regia. Next, PZT is
sputtered to a thickness of 3 μm as the piezoelectric film 26 and patterned with an aqueous
solution of hydrochloric acid. Next, the piezoelectric film 26 is formed. Using a sintered target in
which lead oxide was added in excess to modified PZT mixed with niobium, high frequency
sputtering was performed in an argon atmosphere without heating the substrate to form a PZT
film. Next, after patterning a PZT film, heat treatment is performed at 700 ° C. in an oxygen
atmosphere to form a piezoelectric film 26. Subsequently, titanium is formed in a thickness of 50
Å and gold in a thickness of 2000 Å in this order by sputtering, and the upper electrode 25 is
patterned with an aqueous solution of iodine and potassium iodide.
[0039]
Thereafter, a protective film 49 is formed of photosensitive polyimide to a thickness of 2 .mu.m,
the protective film of the electrode lead-out portion (not shown) is removed by development, and
heat treatment is performed at 400.degree. Next, the surface on the piezoelectric element side on
which the protective film 49 is formed is protected by a jig. Subsequently, the substrate 44 is
immersed in an aqueous solution of potassium hydroxide, and a part of the substrate 44 which is
a single crystal silicon substrate is removed from the opening 77 of the silicon oxide layer 47 to
perform anisotropic etching.
14-04-2019
15
[0040]
As a result, as shown in FIG. 8C, an opening 45 is formed. At this time, the plane orientation of
the substrate 44 which is a single crystal silicon substrate is (110). The direction perpendicular
to the paper is the depth direction of the opening 45. Since the depth direction of the opening 45
is the <1-12> or <-112> direction, the surface of the side wall forming the side of the opening 45
in the depth direction can be set to the (111) plane. When a potassium hydroxide aqueous
solution is used, the ratio of the etching rate of (110) plane to (111) plane of single crystal silicon
is about 300: 1. Therefore, the groove with a depth of 300 μm can be formed with the side
etching suppressed to about 1 μm, and the opening 45 is formed.
[0041]
Note that after forming the opening 45 without the protective film 49, heat treatment may be
performed again at 700 ° C. in an oxygen atmosphere, and a protective film may be further
formed. This is because the piezoelectric characteristics can be further improved by performing
the heat treatment twice on the piezoelectric film 26 (PZT film). Although the detailed reason of
this effect is not clear, it is presumed that the crystal grain size of the PZT constituting the
piezoelectric film is increased and the piezoelectric strain constant is increased as a result.
[0042]
FIG. 9A is a schematic exploded view showing the configuration of the protective jig, and FIG. 9B
is a schematic side sectional view showing the configuration of the protective jig. The protective
jig 78 is a jig for protecting the surface on the piezoelectric element 23 side when the base 44 is
anisotropically etched.
[0043]
As shown in FIG. 9, the protective jig 78 has an opening on one side, and an O-ring 80, a base
body 44, and an O-ring 80 are mounted on a bottomed cylindrical fixing frame 79 having an
opening on its inner wall. The fixing ring 81 is screwed into the inner wall of the fixing frame 79
so as to be fixed. At this time, the surface of the base 44 on which the etching is performed is set
to the opening of the fixing frame 79. It is immersed in etching liquid, such as potassium
14-04-2019
16
hydroxide aqueous solution, in the state shown by FIG.9 (b). At this time, since the sealing ring
81, the O-ring 80, and the surface on which the base 44 is to be etched is sealed, the etching
solution can be prevented from coming into the piezoelectric element side of the base 44. As a
material of the jig, for example, polypropylene can be used.
[0044]
After the piezoelectric element is formed, means for protecting the surface on this side is
provided, and the opening 45 is formed from the surface on the opposite side. Thus, even if a
thin diaphragm and PZT are used, the element chip is well accumulated. 17 can be formed. In the
present embodiment, the means for protecting the surface on the piezoelectric element side is by
means of a jig, but the means is not limited to this, and other means such as thick application of a
photoresist may be used. good.
[0045]
Example 1 Next, the relationship among the dimensions of the aperture and the electrode, the
thickness and dimension of the piezoelectric film, the thickness of the diaphragm and the like will
be described. The inventors first set the planar positional relationship between the opening 45,
the lower electrode 24, the piezoelectric film 26 made of PZT, and the upper electrode 25.
[0046]
First, the lower electrode 24, the piezoelectric film 26, and the upper electrode 25 were
evaluated according to the above manufacturing process up to the upper electrode forming
process.
[0047]
When comparing the case where the upper electrode 25 is larger than the lower electrode 24
and the case where the lower electrode 24 is larger than the upper electrode 25 in reverse, the
leak current between the upper and lower electrodes in the former is about two digits larger than
the latter. I understood it.
14-04-2019
17
This is considered to be due to the large leak current of the PZT film at the lower electrode end.
[0048]
Furthermore, in the case where the lower electrode 24 is larger than the upper electrode 25, the
end of the piezoelectric film 26 in the former case is the case where the piezoelectric film 26 is
larger than the lower electrode 24 and the piezoelectric film 26 is smaller than the lower
electrode 24. The latter could be formed without film peeling or the like while it was curled up
from the vibration film 43 of the base. It is considered that this is because the adhesion between
the piezoelectric film 26 and the vibrating film 43 is insufficient. Therefore, based on the above
results, the magnitude relation of upper electrode 25 ≦ piezoelectric film 26 <lower electrode 24
is established.
[0049]
That is, assuming that the length of the upper electrode 25 in the first direction D1 is Lu, the
length of the piezoelectric film 26 is Lp, and the length of the lower electrode 24 is L1, the
relation of Lu ≦ Lp <L1 is obtained. Assuming that the length of the upper electrode 25 in the
second direction D2 is Wu, the length of the piezoelectric film 26 is Wp, and the length of the
lower electrode 24 is W1, the magnitude relationship is Wu ≦ Wp <W1. As a result, it was
possible to configure the piezoelectric element 23 which has no problem in the manufacturing
process and in which the leak current is suppressed.
[0050]
Next, under the condition of Lu ≦ Lp <L1, the relationship with the length L of the opening 45 in
the first direction D1 is optimized by examining the amount of deformation of the diaphragm 43
at the central portion of the opening 45. I did an experiment. The materials and thicknesses of
the vibrating film 43, the lower electrode 24, the piezoelectric film 26, and the upper electrode
25 are the same as described above. Then, the center of the piezoelectric element 23 is disposed
at the center of the side in the first direction D1 so as to be symmetrical in the left-right direction.
The applied voltage between the lower electrode 24 and the upper electrode 25 was 30V. The
results are shown in Table 1 below when L = 100 μm is fixed and Lu, Lp, and L1 are changed.
14-04-2019
18
[0051]
[0052]
As shown in Table 1 above, the magnitude relationship between the opening 45 and the
piezoelectric film 26 and the lower electrode 24 in the arrangement direction has little influence
on the amount of deformation of the vibrating film 43.
However, the magnitude relationship between the opening 45 and the upper electrode 25 affects
the amount of deformation of the vibrating membrane 43.
[0053]
As shown in the upper part of Table 1, when the length Lu of the upper electrode 25 is larger
than the length L of the opening 45, the amount of deformation of the vibrating film 43 is small.
As shown in steps 2 to 4 of Table 1, when the length Lu of the upper electrode 25 is smaller than
the length L of the opening 45, the amount of deformation of the vibrating film 43 becomes
large. From this result, it is considered that the vibrating film 43 can be efficiently deformed if
the deformed portion of the piezoelectric element 23 is contained in the opening 45. The planar
positional relationship to make such a state is that the length L of the opening 45> the length Lu
of the upper electrode 25 in the first direction D1.
[0054]
Example 2 In order to obtain information on the material of the vibrating membrane 43, the
material of the vibrating membrane 43 was changed in the structure of FIG. 8C, and the amount
of deformation of the vibrating membrane 43 at the central portion of the opening 45 was
examined. The lower electrode 24 was not patterned at all, and was present on the entire surface
of the base 44. As conditions, the length L of the opening 45 in the first direction D1 = 100 μm,
the length of the piezoelectric film 26 is Lp = 94 μm, the length of the upper electrode 25 is Lu
= 88 μm, and the length of the opening 45 in the second direction D2 The thickness is W = 15
mm, the thickness of the piezoelectric film 26 is tp = 3 μm, the thickness tv of the vibrating film
43 is 1 μm, and the applied voltage between the upper and lower electrodes is 30 V.
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[0055]
As the material of the vibration film 43, silicon oxide formed by thermal oxidation, silicon in
which boron is diffused by 10 <21> cm <-3> thermal diffusion, in addition to silicon silicon used
in the above-mentioned Example 1 Five types of zirconium oxide and aluminum oxide formed
were used. The results are shown in Table 2 below.
[0056]
[0057]
According to the following results, as the Young's modulus of the vibrating membrane 43 is
larger, the amount of deformation of the vibrating membrane 43 is larger.
This indicates that when the Young's modulus of the vibrating membrane 43 is small, when the
vibrating membrane 43 is deformed in the lateral direction, it is simultaneously greatly stretched
in the lateral direction, and the deformation in the longitudinal direction is not so large. . In order
to efficiently deform the vibrating film 43 and transmit ultrasonic waves, it is necessary to use
the vibrating film 43 having a large Young's modulus.
[0058]
According to the above results, it is understood that zirconium oxide, silicon nitride silicon, and
aluminum oxide having a large Young's modulus are desirable as the diaphragm material. In
addition, titanium nitride, aluminum nitride, boron nitride, tantalum nitride, tungsten nitride,
zirconium nitride, silicon carbide, titanium carbide, tungsten carbide, and tantalum carbide have
Young's modulus of 2 × 10 <11> N / m <2>. It is the above and it can be said that it is the
material of the desirable diaphragm 43.
[0059]
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20
Furthermore, other components may be added to the material as a main component, or a
material containing two or more of the materials may be used. For example, tungsten carbide is
the main component, titanium carbide, tantalum carbide, a cemented carbide to which a small
amount of cobalt is added, or titanium carbide or titanium carbonitride as the main component,
and a small amount of impurities is used and cermet is used for the vibrating film 43 good.
[0060]
(Example 3) FIG. 10 is a schematic side sectional view showing the structure of an element chip
having a laminated structure of diaphragms. As shown in FIG. 10, a silicon oxide layer 47, a
silicon nitride layer 82, and a silicon oxide layer 83 are stacked on a base 44. The silicon nitride
layer 82 is a material layer having a Young's modulus of 1 × 10 <11> N / m <2> or more,
preferably 2 × 10 <11> N / m <2> or more, and is similar to that of the first embodiment. It is a
layer of silicon nitride. The silicon oxide layer 83 was continuously formed after forming the
silicon nitride layer 82 in the PECVD apparatus in which the silicon nitride layer 82 was formed.
The other elements are the same as in the first embodiment. A vibrating film 84 is formed by the
silicon oxide layer 47, the silicon nitride layer 82 and the silicon oxide layer 83.
[0061]
By providing the silicon oxide layer 83, the adhesion between the lower electrode 24 and the
vibrating film 84 is enhanced. Further, since the stress applied to the piezoelectric film 26 which
occurs at the time of heat treatment in the manufacturing process can be relaxed, the
manufacturing yield can be improved. The vibration characteristics of the vibrating film 84 when
the silicon nitride layer 82 is 1 μm and the silicon oxide layer 83 is 1000 Å are the same as in
Example 1, and the vibration characteristics of the vibrating film 84 are not deteriorated by
providing the silicon oxide layer 83. The
[0062]
In the present embodiment, it is desirable to apply processing temperatures of 710 ° C. or less
when forming the piezoelectric film 26 or thereafter. This is because lead in the piezoelectric film
26 diffuses through the lower electrode 24 to the silicon oxide layer 83 of the vibrating film 84.
Normally, silicon oxide is in a solid state in this temperature range, but silicon oxide in which lead
is diffused becomes a liquid at 714 ° C. or more, and this is ejected to the outside to destroy the
14-04-2019
21
element chip 17. is there.
[0063]
(Example 4) FIG. 11 is a schematic side sectional view showing the structure of an element chip
having a laminated structure of diaphragms. The present embodiment is different from the third
embodiment in that an aluminum oxide layer 85 is inserted between the silicon oxide layer 83
and the lower electrode 24.
[0064]
As shown in FIG. 11, an aluminum oxide layer 85 is formed on the silicon nitride layer 82 and
the silicon oxide layer 83 by sputtering to a thickness of 1000 Å, and the lower electrode 24 is
formed from the top. The other respects are the same as in the third embodiment. A vibrating
film 86 is formed by the silicon oxide layer 47, the silicon nitride layer 82, the silicon oxide layer
83, and the aluminum oxide layer 85.
[0065]
By forming the aluminum oxide layer 85, the diffusion of the lead in the PZT described in the
third embodiment to the diaphragm can be suppressed. As a result, even when the heat
treatment at a high temperature of 710 ° C. or higher is performed, the destruction of the
element chip 17 due to the external ejection of the silicon oxide layer 83 can be prevented, and
the manufacturing yield of the element chip 17 can be improved. Furthermore, since high
temperature and efficient heat treatment at 710 ° C. or higher is possible, the piezoelectric
characteristics of the piezoelectric film 26 can be further improved, and the vibration
characteristics of the piezoelectric element 23 can be improved.
[0066]
It has been found that the effect of providing the aluminum oxide layer 85 can also be obtained
using other materials. As a result of the experiment, the effects were similarly confirmed using
zirconium oxide, tin oxide, zinc oxide and titanium oxide other than the above aluminum oxide. In
14-04-2019
22
addition, a material containing these as the main component and to which an additive is added,
or a material containing as a main component a material containing two or more of these
materials is also applicable. Furthermore, this effect was confirmed not only in the configuration
of the vibrating film having a silicon oxide layer on the surface but also in a single crystal silicon
vibrating film mixed with boron.
[0067]
Example 5 The present inventors conducted the following experiment to determine the
configuration of the lower electrode 24.
[0068]
On the single crystal silicon substrate provided with the silicon oxide layer, titanium and
platinum were continuously formed in this order by the sputtering method as the lower electrode
24.
The thickness of platinum was 2000 Å, and the thickness of titanium was varied from 50 Å to
1000 Å. Titanium is necessary to enhance the adhesion between platinum of the electrode
material and the silicon oxide layer of the diaphragm material.
[0069]
Then, PZT was formed to a film thickness of 1 μm by the method shown in Example 1, heat
treated at 600 ° C. in an oxygen atmosphere for 4 hours, and aluminum was mask-deposited to
a size of 3 mm square as an upper electrode. It formed.
[0070]
In this sample, a voltage was applied between the upper and lower electrodes, and the withstand
voltage characteristics of the piezoelectric film 26 were evaluated.
Here, the withstand voltage of the piezoelectric film 26 is defined as an applied voltage when a
leak current of 100 nA flows. The results are shown in Table 3.
14-04-2019
23
[0071]
[0072]
From the above results, it can be understood that there is a correlation between the titanium film
thickness and the withstand voltage of the piezoelectric film 26, and the withstand voltage
increases as the titanium film becomes thinner.
Also, according to the inventors' observation, subtle protrusions were formed on the platinum
surface, and the density of the protrusions increased with increasing the titanium film thickness.
For example, it was observed that although the number of particles was about 20000 / mm <2>
for 50 Å of titanium, it was about 210,000 / mm <2> for 200 Å of titanium. From this, it is
considered that the minute projections on the platinum surface formed by the heat treatment
reduce the withstand voltage of the piezoelectric film 26.
[0073]
By reducing the thickness of the titanium film from 100 Å to 80 Å, the withstand voltage of the
PZT film was greatly improved from 18 V to 30 V. If the withstand voltage of the piezoelectric
film 26 is improved, the applied voltage can be increased, and the vibration characteristic of the
piezoelectric element 23 can be improved. In addition, even in the state where the piezoelectric
film 26 is thinned, the vibration film 43 can be vibrated, and the productivity in manufacturing
can also be improved.
[0074]
As this withstand voltage value, 10V or less can not stand practical use, and about 20V is still
insufficient, but it can be regarded as a practical area when it greatly exceeds 20V. According to
the above experimental results, it can be seen that the withstand voltage of the PZT film is
significantly improved when the titanium film thickness is 80 Å or less. Therefore, it is desirable
to set the titanium film thickness to 80 Å or less, and the present inventors set the titanium film
thickness to 50 Å also in the above-described embodiment.
14-04-2019
24
[0075]
In the above embodiment, the material of the lower electrode 24 provided on titanium having a
thickness of 80 Å or less is platinum, but it may be an alloy containing platinum. The present
inventors continuously form an alloy of 50 Å of titanium and 70 at% of platinum and 30 at% of
iridium continuously by sputtering on a single crystal silicon substrate provided with a silicon
oxide layer, and heat treat at 600 ° C. for 4 hours in an oxygen atmosphere. As a result of
microscopic observation of the surface of this alloy after heat treatment at 800 ×, no
microprotrusions on the surface were observed. When a PZT film was formed and the withstand
voltage was measured in the same manner as in the above example, a result of 70 V was
obtained, and further improvement of the characteristics was observed.
[0076]
Further, the material of the vibrating film 43 is not limited to single crystal silicon provided with
a silicon oxide layer, and any material described in the above-described embodiment can be
applied.
[0077]
(Effects of the Invention) As described above, in the element chip 17, titanium having a film
thickness of 80 Å or less is used as the adhesion film.
Thereby, the lower electrode 24 can improve the adhesion with the vibrating film 43, and the
withstand voltage of the piezoelectric film 26 can be improved. Therefore, the element chip 17 is
suitably used for the ultrasonic probe 13 that emits ultrasonic waves.
[0078]
Second Embodiment Next, an embodiment of a piezoelectric element will be described with
reference to FIG. The present embodiment is different from the first embodiment in that a
titanium layer is provided between the lower electrode 24 and the piezoelectric film 26.
Description of the same points as the first embodiment will be omitted. Hereinafter, the
piezoelectric element will be described in detail according to the manufacturing process.
14-04-2019
25
[0079]
FIG. 12 is a schematic view for explaining a method of manufacturing an ultrasonic transducer
element chip. In this schematic view, the direction perpendicular to the paper surface is the
depth direction of the opening.
[0080]
As shown in FIG. 12A, a base 44 of monocrystalline silicon having a plane orientation of (110) is
thermally oxidized at 1200 ° C. to form a silicon oxide layer 47 on both sides of the base 44
with a thickness of 5000 Å. Then, boron is diffused from one surface of the base 44 at 1000 °
C. to the base 44 located under the silicon oxide layer 47. As a result, a vibrating film 89 in which
boron is diffused is formed in the base 44 which is single crystal silicon. The thickness of the
vibrating film 89 was 1 μm, and the concentration of boron was 10 <20> cm <-3> (the number
of boron atoms was 10 <20> per 1 cm <3>). Further, a photoresist is formed on both sides of the
substrate 44, and the photoresist on the side opposite to the side on which the vibrating film 89
is provided is patterned to form a mask. Then, the silicon oxide layer 47 is patterned with an
aqueous solution of hydrofluoric acid and ammonium fluoride to form an opening 77. Next, the
photoresist is peeled off. The depth direction of the opening 77, that is, the direction
perpendicular to the paper surface, is taken as a <1 -12> or <-112> direction. Subsequently, a
tantalum layer 93 containing oxygen, a lower electrode 90, a titanium layer 94 containing
oxygen, and a piezoelectric film 91 are laminated in this order on the vibrating film 89 side of
the base body 44. Metal tantalum is stacked 600 Å on the silicon oxide layer 47 on the vibrating
film 89 side to form a tantalum layer 93. Next, 50 Å of titanium and 2000 Å of platinum are
laminated on the adhesion layer as the lower electrode 90. Subsequently, a titanium layer 94
with a thickness of 50 Å is formed by sputtering.
[0081]
Next, as shown in FIG. 12B, the lower electrode 90 and the titanium layer 94 are patterned into a
predetermined shape using a photolithographic method and an etching method. Furthermore, the
substrate heating in an argon atmosphere is performed using a sintered body target having a
thickness of 3 μm and a composition Pb 0.95 Sr 0.05 Zr 0.28 Ti 0.35 Mg 0.123 Nb 0.247 O 3
(90 mol%) + PbO (10 mol%). The high frequency sputtering film formation is performed without.
14-04-2019
26
Next, annealing is performed in an oxygen atmosphere at 650 ° C. for one hour and 900 ° C.
for one hour. By the above steps, the tantalum layer 93 containing oxygen, the lower electrode
90, the titanium layer 94 containing oxygen, and the piezoelectric film 91 were formed. In fact,
after performing annealing at 650 ° C. for 1 hour and 900 ° C. for 1 hour in an oxygen
atmosphere, a portion where the piezoelectric film 91 is not present above the lower electrode
90 is analyzed by X-ray diffraction. Diffraction lines were observed, and it was confirmed that a
titanium layer 94 containing titanium dioxide was present.
[0082]
Then, the piezoelectric film 91 is patterned with a borofluoric acid aqueous solution and the
lower electrode 90 with aqua regia aqueous solution. Next, the upper electrode 92 is placed on
the piezoelectric film 91. Titanium is formed to a thickness of 50 Å and gold to a thickness of
2000 Å by sputtering, and is patterned with an aqueous solution of iodine and potassium iodide.
Subsequently, a protective film 49 is formed of photosensitive polyimide to a thickness of 2
.mu.m, the protective film of the electrode lead-out portion (not shown) is removed by
development, and heat treatment is performed at 400.degree.
[0083]
As shown in FIG. 12C, the surface on the side of the piezoelectric element on which the
protective film 49 is formed is protected by a jig and immersed in a potassium hydroxide
aqueous solution. Anisotropic etching of the substrate 44 of single crystal silicon is performed
from the opening 77 of the silicon oxide layer 47 to form an opening 45. At this time, the plane
orientation of the substrate 44 of single crystal silicon is (110), and the depth direction of the
opening 77 is <1 −1 2> or <−1 12 2> direction. The surface of the side wall that forms the side
in the depth direction can be a (111) surface. When a potassium hydroxide aqueous solution is
used, the ratio of the etching rate of (110) plane to (111) plane of single crystal silicon is about
300: 1, and a groove of 300 μm depth is formed with side etching of about 1 μm. And an
opening 45 is formed. The piezoelectric element 95 is formed by the above steps.
[0084]
In the element chip of the above embodiment, the thickness of titanium metal to be sputterdeposited on the lower electrode 90 was changed. In the above manufacturing process, annealing
14-04-2019
27
up to 650 ° C. for 1 hour and 900 ° C. for 1 hour in an oxygen atmosphere was performed,
and observation was performed visually, with a metallographic microscope, and a scanning
electron microscope (SEM). The results are shown in Table 4.
[0085]
[0086]
From the above results, it can be seen that by forming the titanium layer 94 containing titanium
dioxide on the lower electrode 90, the adhesion between the piezoelectric film 91 and the lower
electrode 90 is improved, and the peeling phenomenon is eliminated.
In addition, when the thickness of titanium metal is 200 Å, a cavity is generated in the lower part
of the PZT, which is caused by the reaction between the lead oxide in the piezoelectric film 91
and the titanium layer 94 containing oxygen to liquefy. It is considered to be attributable.
Therefore, it is desirable that the thickness of the titanium layer 94 containing titanium dioxide is
not so thick. When the metal titanium is annealed in an oxygen atmosphere at 650 ° C. for 1
hour and at 900 ° C. for 1 hour, the thickness of the film is about twice that before annealing,
which is confirmed by SEM observation of the inventor. The thickness of the contained titanium
layer 94 is preferably 200 Å or less.
[0087]
The oxygen-containing titanium layer 94 may be an oxygen-containing titanium alloy, such as a
titanium-tantalum alloy, a titanium-nickel alloy, or a titanium-platinum alloy.
[0088]
Further, the constituent elements and materials of the piezoelectric element 95 are not limited to
those in the above embodiments.
For example, it is also possible to further increase the thickness of the piezoelectric film 91, and
the material is not limited to PZT of a specific composition, and the composition ratio and the
type of additive may be changed. In addition to PZT, a lead-containing material such as lead
14-04-2019
28
titanate may be used. Moreover, the manufacturing method may use other methods, such as a sol
gel method. The lower electrode 90 may also use chromium, nickel, tungsten or the like for the
adhesion layer, and the platinum layer may use a platinum-rhodium alloy, a platinum-iridium
alloy, a platinum-titanium alloy or the like. Alternatively, the tantalum layer 93 containing oxygen
may be suddenly formed by a chemical vapor deposition (CVD) method or a sputtering method
using an oxide target. Furthermore, a low valence oxide such as a tantalum dioxide layer may be
contained in the layer.
[0089]
Further, the piezoelectric strain constant d31 contains titanium dioxide on the lower electrode 90
while the piezoelectric film 91 in the case where there is no titanium layer 94 containing
titanium dioxide on the lower electrode 90 is 150 pC / N. The piezoelectric film 91 when the
titanium layer 94 is provided is as large as 170 pC / N, and the vibration characteristic of the
vibrating film 89 when the latter is used is also improved. The piezoelectric film 91 is made of
PZT having the above composition after annealing at 650 ° C. for 1 hour and 900 ° C. for 1
hour in an oxygen atmosphere. Therefore, by providing the titanium layer 94 containing titanium
dioxide, the piezoelectric strain constant d31 is increased, and the vibration characteristic of the
vibrating film 89 is also improved, which is an effect that was not originally conceived.
[0090]
(Modification 1) Next, a modification of the piezoelectric element will be described with reference
to FIG. The present modification is different from the second embodiment in that zirconium oxide
is used for the vibrating film 89. Description of the same points as the second embodiment will
be omitted. Hereinafter, the piezoelectric element will be described in detail according to the
manufacturing process.
[0091]
FIG. 13 is a schematic view for explaining a method of manufacturing an ultrasonic transducer
element chip. As shown in FIG. 13A, a silicon oxide layer 47 is formed on both sides of a
substrate 44 of single crystal silicon of plane orientation (110). Thereafter, the silicon oxide layer
47 on one side is patterned to form an opening 77 for forming the opening 45. At the same time
as this step, the silicon oxide layer 47 on the surface opposite to the opening 77 is removed.
14-04-2019
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[0092]
As shown in FIG. 13B, a metal zirconium film is formed on the entire surface from which the
silicon oxide layer 47 has been removed, and thermal oxidation is performed. Thus, a vibrating
film 96 made of zirconium oxide is formed. The vibrating film 96 made of zirconium oxide has a
larger Young's modulus than the vibrating film 89 made of silicon. Therefore, when the same
voltage is applied to the piezoelectric film 91, the deformation amount and the generated
pressure of the vibrating film 96 on the opening 45 are larger than those of the vibrating film 89
in the case of using zirconium oxide. Therefore, the vibration characteristics of the vibrating film
96 are also good.
[0093]
As the material of the vibration film 96, not only ordinary zirconium oxide (zirconia) but
stabilized zirconia to which yttrium etc. is added, alumina, aluminum nitride, zirconium nitride
etc. may be used, and a laminated structure of them The vibrating film 96 may be formed by
[0094]
As shown in FIG. 13C, the lower electrode 90, the titanium layer 94, the piezoelectric film 91, the
upper electrode 92, and the protective film 49 are disposed on the vibrating film 96 to form the
piezoelectric element 97.
[0095]
(Effects of the Invention) As described above, the element chip according to the present invention
is provided with the titanium layer 94 which is titanium containing titanium dioxide or an alloy
layer containing titanium on the lower electrode 90.
Desirably, by setting the thickness of the titanium layer 94 to 200 Å or less, the adhesion
between the lower electrode 90 and the piezoelectric film 91 can be improved.
[0096]
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30
Third Embodiment Next, an embodiment of an element chip will be described with reference to
FIGS.
The present embodiment is different from the first embodiment in that the piezoelectric film 26
of the piezoelectric element 23 has a piezoelectric active portion in which distortion occurs and a
piezoelectric inactive portion in which no distortion occurs. Description of the same points as the
first embodiment will be omitted. Hereinafter, the piezoelectric element will be described in detail
according to the manufacturing process.
[0097]
FIG. 14 is a schematic plan view showing the structure of the element chip. As shown in FIG. 14,
the element chip 100 is provided with a square base 101. One side of the outer periphery of the
base 101 extends in the first direction D1, and the other side extends in the second direction D2.
The lower electrode 102 and the lower electrode film 103 for wiring that extend in the second
direction D2 are provided on the base 101. Then, the piezoelectric element 104 is disposed
across the lower electrode 102 and the lower electrode film 103 for wiring. Seven piezoelectric
elements 104 are arranged in the second direction D2 along the lower electrode 102. And, the
array of the piezoelectric elements 104 is arranged in three rows in the first direction D1.
Therefore, 21 piezoelectric elements 104 are provided on the element chip 100. The number of
piezoelectric elements 104 installed in one element chip 100 is not particularly limited.
[0098]
Fig.15 (a) is a model top view which shows the structure of an ultrasonic transducer element,
FIG.15 (b) is a principal part model sectional side view which shows the structure of an ultrasonic
transducer element. FIG. 16 is a schematic plan view showing the structure of the ultrasonic
transducer element.
[0099]
As shown in FIG. 15, an opening 105 is formed in the base 101 for each piezoelectric element
104. An elastic film 108 is disposed on the base 101. The elastic film 108 is a 1 to 2 μm thick
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film made of silicon dioxide formed by thermal oxidation. The lower electrode 102 and the lower
electrode film 103 for wiring are disposed on the elastic film 108. The thickness of the lower
electrode 102 is, for example, about 0.5 μm. The lower electrode 102 constituting the
piezoelectric element 104 is continuously provided in a region facing the plurality of openings
105 arranged in parallel. The lower electrode 102 is patterned near one longitudinal end of the
opening 105. An end of the lower electrode 102 is an end of the piezoelectric active portion 106.
A lower electrode film 103 for wiring is provided in each of the openings 105 in a region
opposed to the vicinity of the end of the other end of the opening 105 in the longitudinal
direction. The lower wiring electrode film 103 is disposed from the region facing the opening
105 to the peripheral wall, and is discontinuous with the lower electrode 102. The lower
electrode film 103 for wiring is used as a wiring of the piezoelectric element 104.
[0100]
It is preferable that the distance between the lower electrode 102 and the lower electrode film
103 for wiring and the distance between the lower electrode films 103 for wiring be formed at
such a narrow width that at least the respective insulation strength can be maintained.
[0101]
The piezoelectric film 107 is provided on the lower electrode 102 and the lower electrode film
103 for wiring, and the upper electrode 109 is provided on the piezoelectric film 107.
The thickness of the piezoelectric film 107 is, for example, about 1 μm. The thickness of the
upper electrode 109 is, for example, about 0.1 μm.
[0102]
The piezoelectric element 104 refers to a portion including the lower electrode 102, the
piezoelectric film 107, and the upper electrode 109. In general, one of the electrodes of the
piezoelectric element 104 is used as a common electrode, and the other electrode and the
piezoelectric film 107 are patterned for each opening 105. Here, a portion which is formed of
one of the patterned electrodes and the piezoelectric film 107 and a piezoelectric strain is
generated by application of a voltage to both electrodes is referred to as a piezoelectric active
portion 106. In the present embodiment, the lower electrode 102 is used as a common electrode
of the piezoelectric element 104 and the upper electrode 109 is used as an individual electrode
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of the piezoelectric element 104. However, there is no problem even if this is reversed due to the
drive circuit and wiring. In any case, the piezoelectric active portion is formed for each of the
openings 105. Further, here, the piezoelectric element 104 and the vibrating plate which is
displaced by the drive of the piezoelectric element 104 are collectively referred to as a
piezoelectric actuator.
[0103]
The piezoelectric film 107 and the upper electrode 109 are provided in a region facing the
opening 105. One end of the upper electrode 109 is extended onto the lower electrode film 103
for wiring. The upper electrode 109 and the lower electrode film 103 for wiring are connected
by the lead electrode 110. Further, the shape of the lower electrode film 103 for wiring is not
particularly limited, but as shown in FIG. 16, it is preferable to cover at least the edge of the
opening 105. As a result, the rigidity of the elastic film 108 is held high, and the occurrence of
cracks and the like in the elastic film 108 can be prevented.
[0104]
Returning to FIG. 15, in such a configuration, the lower electrode 102 and the piezoelectric film
107 and the upper electrode 109 present on the lower electrode 102 constitute a piezoelectric
active portion 106. The piezoelectric element 104 at a place where the lower electrode 102 is
not provided is a piezoelectric non-active portion 111 which is not substantially driven.
Therefore, the piezoelectric non-active portion 111 is continuously provided from the
longitudinal end of the opening 105 and includes a location facing the lower electrode film 103
for wiring.
[0105]
Therefore, the piezoelectric element 104 in a portion located at a part of the boundary between
the opening 105 and the peripheral wall is the piezoelectric inactive portion 111 which is not
driven by voltage application to the piezoelectric active portion 106. . For this reason, there is no
possibility of peeling of the piezoelectric film 107 or the like at the longitudinal direction end of
the opening 105 or generation of a crack due to repeated displacement. Further, since the
piezoelectric film 107 and the upper electrode 109 are extended onto the lower electrode film
103 for wiring, it is not necessary to form a contact hole. That is, it is not necessary to form an
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insulator film for providing a contact hole on the upper electrode 109. Therefore, the decrease in
displacement due to the thickness of the insulator film of the piezoelectric active portion 106 is
eliminated. In addition, the number of manufacturing processes can be reduced, and the cost can
be reduced.
[0106]
Next, a process of forming a piezoelectric film or the like on a substrate 101 made of a silicon
single crystal substrate will be described with reference to FIGS. 17 to 19 are schematic views for
explaining a method of manufacturing a piezoelectric element. 17 and 19 are schematic crosssectional views in the second direction D2, and FIG. 18 is a schematic cross-sectional view in the
first direction D1.
[0107]
First, as shown in FIG. 17A, a wafer of a silicon single crystal substrate to be a base 101 is
thermally oxidized in a diffusion furnace at about 1100 ° C. to form an elastic film 108 made of
silicon dioxide.
[0108]
Next, as shown in FIG. 17B, the lower electrode 102 is formed by sputtering.
As a material of the lower electrode 102, platinum or the like is preferable. This is because the
piezoelectric film 107 formed by sputtering or sol-gel method needs to be crystallized by firing at
a temperature of about 600 to 1000 ° C. in the air or oxygen atmosphere after film formation. It
is. That is, the material of the lower electrode 102 should be able to maintain conductivity under
such high temperature and oxidizing atmosphere. In particular, when lead zirconate titanate
(PZT) is used as the piezoelectric film 107, it is desirable that the change in conductivity due to
the diffusion of lead oxide is small, and for these reasons, platinum is preferable.
[0109]
Next, as shown in FIG. 17C and FIG. 18, the lower electrode 102 is patterned to form an entire
pattern, and in the region corresponding to one end in the longitudinal direction of each opening
105, the openings 105 are respectively formed. A lower electrode film 103 for wiring is formed
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extending from the opposing region to the upper side of the peripheral wall.
[0110]
Next, as shown in FIG. 17D, the piezoelectric film 107 is formed.
It is preferable that crystals of this piezoelectric film 107 be oriented. For example, in the present
embodiment, a so-called sol-gel method in which a so-called sol obtained by dissolving and
dispersing a metal organic substance in a catalyst is coated, dried and gelled and calcined at a
high temperature to obtain a piezoelectric film 107 made of metal oxide To form a piezoelectric
film 107 in which crystals are oriented.
[0111]
In the process of forming the piezoelectric film 107, the amorphous thin film is heated to be
crystallized or in any process of the heat treatment process provided after this process, under an
atmosphere of 100% water, at 700.degree. It is preferred to include a process step of treating
under temperature and under a pressure of 200 atmospheres or less.
[0112]
In the PZT thin film formed by the sol-gel method, by containing water in the degreasing
atmosphere, it is possible to control the amount of oxygen in the PZT thin film.
Then, it is possible to form an oxide PZT thin film with less oxygen deficiency. In addition, it is
thought that the stress applied to the PZT thin film at the time of degreasing and thereafter can
be relaxed by containing water in the atmosphere at the degreasing time. Therefore, the
occurrence of cracks can be suppressed. In addition, since the crystallization of the oxide ceramic
thin film is performed by hydrothermal treatment in water, the thin film and other materials are
not affected. Therefore, it is possible to select a wide range of materials, and to provide a low cost
and environmentally friendly manufacturing method.
[0113]
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35
As a material of the piezoelectric film 107, a lead zirconate titanate based material is preferable.
The method of forming the piezoelectric film 107 is not particularly limited, and may be formed
by sputtering, for example.
[0114]
Furthermore, a precursor film of lead zirconate titanate may be formed by a sol-gel method or
sputtering method, and then crystal growth may be performed at a low temperature by a high
pressure treatment method in an alkaline aqueous solution.
[0115]
In any case, in the piezoelectric film 107 thus formed, crystals are preferentially oriented unlike
the bulk piezoelectric material, and in the present embodiment, the piezoelectric film 107 has
crystals formed in a columnar shape. It is done.
The preferred orientation means that the orientation direction of the crystal is not disordered,
and a specific crystal face is oriented in a substantially constant direction. Further, a thin film in
which crystals are columnar refers to a state in which crystals of a substantially cylindrical body
are gathered together in the plane direction to form a thin film in a state in which the central axis
is substantially aligned with the thickness direction. Of course, it may be a thin film formed of
preferentially oriented granular crystals. The thickness of the piezoelectric film thus
manufactured in the thin film process is generally 0.5 to 5 μm.
[0116]
Next, as shown in FIG. 17E, the upper electrode 109 is deposited. The upper electrode 109 may
be made of a highly conductive material, and many metals such as aluminum, gold, nickel, and
platinum, a conductive oxide, and the like can be used. In the present embodiment, platinum is
deposited by sputtering.
[0117]
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Thereafter, as shown in FIG. 19A, only the piezoelectric film 107 and the upper electrode 109 are
etched to pattern the piezoelectric active portion. The above is the film formation process. After
film formation is performed as described above, as shown in FIG. 19B, the silicon single crystal
substrate is anisotropically etched with an alkaline solution to form the openings 105 and the
like. The piezoelectric element 104 shown in FIG. 15 is formed by the above steps.
[0118]
In the present embodiment, the piezoelectric film 107 and the upper electrode 109 are formed in
the area facing the opening 105, but the invention is not limited to this. For example, the
piezoelectric film 107 and the upper electrode 109 extend to the area facing the peripheral wall.
May be In the example described above, the piezoelectric non-active portion 111 is formed by
removing the lower electrode 102. However, the present invention is not limited thereto. For
example, a low dielectric insulating layer may be formed between the piezoelectric film 107 and
the upper electrode 109. The piezoelectric film 107 may be partially formed by doping or the
like to make it inactive.
[0119]
As described above, according to the present embodiment, the contact hole is formed
continuously from the piezoelectric active portion 106 by providing the piezoelectric inactive
portion 111 having the piezoelectric film 107 but not substantially driven. Therefore, voltage can
be applied to the piezoelectric active portion 106, and the piezoelectric active portion 106 can be
provided in the region facing the opening 105, so that displacement characteristics and reliability
can be improved.
[0120]
(Modification 1) FIGS. 20 and 21 are main part schematic cross-sectional views showing the
structure of the piezoelectric element, and FIG. 22 is a main part schematic plan view showing
the structure of the piezoelectric element.
This modification is another example of the wiring method of the piezoelectric active portion
106, and as shown in FIG. 20, the wiring lower electrode film 103 is provided on the peripheral
wall without being provided in the region facing the opening 105. Except for this, the third
embodiment is the same as the third embodiment. Of course, even in such a configuration, the
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same effect as that of the third embodiment can be obtained.
[0121]
In the third embodiment, the lower electrode film 103 for wiring is provided on the outer side of
the lower electrode 102. However, the present invention is not limited to this. For example, as
shown in FIG. A lead electrode 112 connected to the upper electrode 109 of the piezoelectric
non-active portion 111 and extending to the end of the substrate may be separately provided.
That is, the lead electrode 112 may be an electrode having the functions of the lead electrode
110 and the lower electrode film 103 for wiring.
[0122]
The piezoelectric film 107 and the upper electrode 109 constituting the piezoelectric non-active
portion 111 extending from the end of the opening 105 onto the peripheral wall are not
particularly limited. For example, as shown in FIG. It is preferable that a wide portion 113 wider
than the opening 105 be formed in the vicinity of the end of the opening 105 so as to cover the
end of the opening 105. Thereby, the rigidity of the diaphragm in the vicinity of the end portion
of the opening 105 is held high, and the occurrence of a crack or the like of the diaphragm can
be prevented.
[0123]
(Modification 2) FIGS. 23 and 24 are main part schematic plan views showing the structure of a
piezoelectric element. In this modification, as shown in FIG. 23, the lower electrode discontinuous
with the lower electrode 102 is provided under the piezoelectric inactive portion 111 in a region
facing the boundary between the end of the opening 105 and the peripheral wall. This is an
example in which the film 114 is provided. That is, in the vicinity of the end on the side where
the piezoelectric film 107 of the opening 105 and the upper electrode 109 are extended, the
lower electrode film removed portion 115 from which the lower electrode 102 is removed is
arranged along the shape of the opening 105. It is provided in the shape of a narrow groove in
the direction. The third embodiment is the same as the third embodiment except that a
discontinuous lower electrode film 114 is discontinuous with the lower electrode 102 of the
piezoelectric active portion 106 at the boundary between the end of the opening 105 and the
peripheral wall.
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[0124]
Here, the width of the lower electrode film removing portion 115 for separating the lower
electrode 102 and the discontinuous lower electrode film 114 needs to be at least a width
capable of maintaining the insulation strength between the lower electrode 102 and the
discontinuous lower electrode film 114. However, it is preferable to maintain the rigidity of the
elastic membrane 108 as narrow as possible.
[0125]
Moreover, in such a configuration, the discontinuous lower electrode film 114 is a floating
electrode which is not electrically connected to any other.
The piezoelectric film 107 and the upper electrode 109 present on the lower electrode 102
constitute the piezoelectric active portion 106 which becomes a substantial driving part, and the
piezoelectric film 107 and the upper electrode 109 on the discontinuous lower electrode film
114 are strong It is not driven.
[0126]
Therefore, the boundary portion between the opening 105 and the peripheral wall is not strongly
driven even by voltage application to the piezoelectric active portion 106. Therefore, the rigidity
of the elastic film 108 at the longitudinal end of the opening 105 is high, and the destruction of
the elastic film 108 or the destruction of the piezoelectric film 107 can be prevented at this part.
[0127]
In this modification, the discontinuous lower electrode film 114 is formed along the direction in
which the plurality of openings 105 are arranged, but the present invention is not limited to this.
For example, as shown in FIG. 24, each piezoelectric active portion 106 may be separated. As a
result, the piezoelectric film 107 and the upper electrode 109 on the discontinuous lower
electrode film 114 become the piezoelectric inactive portion 111 which is not completely driven,
and the breakage of the elastic film 108 or the piezoelectric film 107 is more assured. Can be
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prevented.
[0128]
Moreover, in this modification, although the discontinuous lower electrode film 114 is a floating
electrode which is not electrically connected to other portions, the present invention is not
limited to this, for example, the time constant of charging is piezoelectric The electrode layer may
be connected through a resistor having a predetermined resistance value so as to be larger than
the drive pulse of the body active unit 106.
[0129]
(Modification 3) FIG. 25 is a schematic plan view of the main part showing the structure of the
piezoelectric element.
FIG. 26 (a) is a schematic plan view of the main part showing the structure of the piezoelectric
element, and FIG. 26 (b) is a schematic cross-sectional side view of the main part showing the
structure of the piezoelectric element.
[0130]
In this modification, as shown in FIG. 25, an intermediate electrode film 116 separated by the
lower electrode film removing portion 115 and not connected to any other is provided between
the lower electrode films 103 for wiring. The configuration is the same as that of the third
embodiment.
[0131]
With such a configuration, the width of the lower electrode film removing portion 115 for
separating the lower electrode films 103 for wiring can be narrowed.
That is, the intermediate electrode film 116 is provided between the lower electrode films 103
for wiring. Therefore, even if the width of the lower electrode film removing portion 115 is
narrowed, these insulation strengths can be reliably maintained. As a result, the rigidity of the
elastic film 108 is further enhanced, and the destruction of the elastic film 108 or the destruction
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of the piezoelectric film 107 can be prevented at the boundary between the opening 105 and the
peripheral wall, as in the above embodiment.
[0132]
In the above-described modification, the lower electrode film removing portion 115 between the
lower electrode 102 and the lower electrode film 103 for wiring can maintain the insulation
strength between each lower electrode 102 and the lower electrode film 103 for wiring. It has a
width of Not limited to this, for example, as shown in FIG. 26, the upper electrode 109 in a
portion where dielectric breakdown is likely to occur, such as both sides in the width direction of
the piezoelectric active portion 106, may be removed. Then, an inactive portion 117 may be
provided in which the piezoelectric film 107 not substantially driven is left. Thereby, the
insulation strength can be more reliably maintained. Of course, it goes without saying that the
upper electrode 109 may not be removed if the piezoelectric film 107 is not driven.
[0133]
(Modification 4) FIG. 27 (a) is a schematic plan view of the main part showing the structure of
the piezoelectric element. FIG. 27 (b) is a schematic side sectional view of the main part showing
the structure of the piezoelectric element. FIG. 28 is a schematic view for explaining a method of
manufacturing a piezoelectric element.
[0134]
In this modification, as shown in FIG. 27, instead of providing the lower electrode film 103 for
wiring, the piezoelectric film 107 and the upper electrode 109 to be the piezoelectric non-active
portion 111 extend from the region facing the opening 105 to above the peripheral wall. It is
extended. Although not shown, in the vicinity of the end, for example, an external wiring such as
a flexible cable and the upper electrode 109 are directly connected. In addition, the lower
electrode 102 is basically provided in a region facing the opening 105. The lower electrode 102
is extended from the end opposite to the piezoelectric non-active portion 111 to the peripheral
wall of the opening 105 to be a common electrode of each piezoelectric element 104. Other than
this, the third embodiment is the same as the third embodiment.
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[0135]
Of course, the same effect as that of the third embodiment can be obtained by such a
configuration. Further, the lower electrode 102 and the upper electrode 109 are extended from
the longitudinal direction end of the opening 105 in the opposite direction to the peripheral wall.
With this structure, the wiring can be easily drawn out without shorting the lower electrode 102
and the upper electrode 109.
[0136]
When the piezoelectric film 107 is continuously formed from the opening 105 to the peripheral
wall as in the present modification, the crystal structure of the piezoelectric film 107 is the same
on the lower electrode 102 and the elastic film 108. Is preferred. Therefore, it is preferable to
form the piezoelectric film 107 as follows.
[0137]
That is, as shown in FIG. 28A, before forming the piezoelectric film 107, a crystal seed 118 made
of titanium or titanium oxide is formed into an island shape by sputtering on the lower electrode
102 and the elastic film 108. . Thereafter, as shown in FIG. 28B, the piezoelectric precursor layer
121 is not formed and is deposited. Thereafter, as shown in FIG. 28C, the piezoelectric precursor
layer 121 is crystallized by firing to form a piezoelectric film 107.
[0138]
Further, in the case of using the method of forming the crystal seed 118 in this manner, the
elastic film 108 is at least one kind of material selected from materials having good adhesion
with the piezoelectric film 107, for example, constituent elements of the piezoelectric film 107. It
is preferable to be formed of an oxide or nitride of an element such as zirconium oxide.
[0139]
Here, in the case where the piezoelectric film 107 is formed on the lower electrode 102 such as
platinum, a technology for forming crystal seeds and orienting crystals in substantially one
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direction has already been filed.
However, in the special structure in which the piezoelectric film 107 is formed after the lower
electrode 102 is patterned as in the present modification, the elastic film 108 is formed even if
the crystal seed is formed on the lower electrode 102 in advance. Above, there is a problem that
the crystal structure is different and a crack is easily generated. Therefore, in the present
modification, the crystal seed 118 is also formed on the elastic film 108, thereby making the
crystal structure of the piezoelectric film 107 substantially the same on the lower electrode 102
and the elastic film 108, thereby generating cracks and abnormalities. Prevent the generation of
stress. The crystal seeds on the elastic film 108 may be formed simultaneously after patterning
the lower electrode 102, or after forming the crystal seeds on the lower electrode 102 and
further patterning, only the elastic film 108 is separately formed. You may go. In addition, in the
case of performing separately, the crystal seed may be formed in a film shape instead of an island
shape.
[0140]
(Modification 5) FIG. 29 is a main part schematic plan view showing the structure of a
piezoelectric element. In this modification, as shown in FIG. 29, the present embodiment is
carried out except that the piezoelectric inactive portion 111 is provided in a region opposed to
the peripheral wall in the width direction of the opening 105 from the substantially central
portion of the piezoelectric active portion 106. It is the same as the form.
[0141]
With such a configuration, concentration of current to the piezoelectric film 107 in the vicinity of
the connection portion between the piezoelectric active portion 106 and the piezoelectric nonactive portion 111 is suppressed, in addition to the same effect as that of the present
embodiment. It is possible to prevent the breakage of the piezoelectric film 107 and the like.
[0142]
(Modification 6) FIG. 30 is a main part schematic plan view showing the structure of the
piezoelectric element.
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This modification is the same as modification 4 except that the narrow portion 122 is formed on
the side of the piezoelectric active portion 106 of the piezoelectric inactive portion 111 as shown
in FIG. The width of the narrow portion 122 is narrower than the width of the piezoelectric active
portion 106 located in a region opposed to the longitudinal end of the opening 105. In the
narrow portion 122, the upper electrode 109 and the piezoelectric film 107 are narrow.
[0143]
In such a configuration, since the upper electrode 109 and the piezoelectric film 107 do not exist
around the narrow portion 122 at the end of the opening 105, the elastic film 108 is easily
displaced. Therefore, it is possible to improve the displacement amount of the elastic film 108 by
driving the piezoelectric active portion 106 at this end.
[0144]
In the present modification, the upper electrode 109 and the piezoelectric film 107, which are
the piezoelectric non-active portion 111, are formed to be narrow. However, the present
invention is not limited thereto. For example, only the upper electrode 109 is formed to be
narrow. You may do it.
[0145]
(Modification 7) FIG. 31 (a) is a schematic plan view of the main part showing the structure of
the piezoelectric element.
FIG. 31 (b) is a schematic side sectional view of the main part showing the structure of the
piezoelectric element. In the present modification, as shown in FIG. 31, a narrow portion 123 in
which a part of the lower electrode 102 protrudes is formed in the vicinity of the end of the
opening 105. The lower electrode 102 at the boundary between the piezoelectric active portion
106 and the piezoelectric inactive portion 111 has both sides in the width direction of the
opening 105 removed. Thus, a part of the lower electrode 102 is a narrow part 123 narrower
than the other parts. Further, the narrow portion 123 is formed to be narrower than the width of
the piezoelectric film 107 in the region facing the opening 105, and the third embodiment is the
same as the third embodiment except that both widthwise end surfaces are covered by the
piezoelectric film 107. Is the same as the embodiment of FIG.
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[0146]
With such a configuration, the upper electrode 109 and the side surface of the lower electrode
102 are reliably insulated in the vicinity of the end of the lower electrode 102 of the opening
105, that is, at the end of the piezoelectric active portion 106. There is no discharge between
them. Therefore, dielectric breakdown or the like of the piezoelectric film 107 can be prevented.
[0147]
(Modification 8) FIG. 32 (a) is a schematic plan view of the main part showing the structure of
the piezoelectric element. 32 (b) and (c) are schematic side sectional views of the main part
showing the structure of the piezoelectric element. In this modification, as shown in FIGS. 32A
and 32B, the narrow portion 123 of the lower electrode 102 is formed in the region facing the
opening 105, and the narrow portion 123 is piezoelectric. The width is wider than the width of
the body film 107. Then, it is the same as the modification 7 except that the piezoelectric film
107 and the upper electrode 109 are extended to the peripheral wall above the narrow portion
123 to form the piezoelectric non-active portion 111.
[0148]
Here, in general, as shown by a graph called a Paschen curve, it is known that when the distance
between the electrodes is equal to or less than a fixed value, no discharge occurs between them.
For example, in the present modification, the distance between the end surface in the width
direction of the narrow portion 123 and the end surface in the width direction of the upper
electrode 109 may be about 10 μm or less. In the present modification, the distance between
them may be about 7 μm. I made it.
[0149]
Therefore, even with such a configuration, as in the seventh modification, the discharge between
the upper electrode 109 and the lower electrode 102 at the longitudinal end of the opening 105
is prevented, and the dielectric breakdown of the piezoelectric film 107 is suppressed. Be
[0150]
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Although the narrow portion 123 is provided in the region facing the opening 105 in this
modification, the present invention is not limited to this.
The distance between the end face in the width direction of the narrow portion 123 and the end
face in the width direction of the upper electrode 109 may be a distance at which no discharge
occurs between the upper electrode 109 and the lower electrode 102. For example, as shown in
FIG. 32C, the narrow portion 123 may be extended to the width direction peripheral wall of the
opening 105.
[0151]
(Modification 9) FIG. 33 is a schematic plan view of the main part showing the structure of the
piezoelectric element. In this modification, as shown in FIG. 33, the narrow portion 123 of the
lower electrode 102 has a substantially trapezoidal shape whose width gradually decreases
toward the tip end. The third embodiment is the same as the eighth modification except that at
least the tip of the narrow portion 123 is covered with the piezoelectric film 107 in the region
facing the opening 105.
[0152]
As a result, the piezoelectric film 107 tends to be thin at the end of the lower electrode 102. As a
result, since concentration of the electric field is likely to occur, dielectric breakdown or the like
of the piezoelectric film 107 is particularly likely to occur. Then, the tip portion of the narrow
portion 123 is covered by the piezoelectric film 107, and the lower electrode 102 and the upper
electrode 109 are insulated. Therefore, no discharge occurs between them, and dielectric
breakdown or the like of the piezoelectric film 107 can be prevented.
[0153]
(Modification 10) FIG. 34 (a) is a schematic plan view of the main part showing the structure of
the piezoelectric element. FIG. 34 (b) is a schematic side sectional view of the main part showing
the structure of the piezoelectric element. In this modification, as shown in FIG. 34, the
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piezoelectric film 107 and the upper electrode 109 have a width narrower than that of the
piezoelectric active portion 106 and extend continuously from one end in the longitudinal
direction of the opening 105 to the region facing the peripheral wall. The piezoelectric body nonactive portion 111 is provided. The upper electrode 109 and the external wiring are connected
near the end of the opening 105. On the other hand, the lower electrode 102 is basically formed
so as to cover a region facing each opening 105. However, in the region where the piezoelectric
film 107 and the upper electrode 109 are extended, that is, the region where the piezoelectric
inactive portion 111 is extended, the lower electrode 102 is removed with a width narrower than
the width of the opening 105. The film removing unit 115 is provided. Other than this is the
same as the third embodiment.
[0154]
Here, in the portion where the piezoelectric film 107 and the upper electrode 109 extend on the
peripheral wall from the end of the opening 105 and the lower electrode film removed portion
115, the edge of the upper electrode 109 is the lower electrode film from above the lower
electrode 102. It is preferable that the first direction 109a intersecting on the removing portion
115 does not coincide with the second direction 109b in which the upper electrode 109 is
extended on the peripheral wall. That is, it is preferable that the angle between the direction of
the current flowing to the portion where the upper electrode 109 crosses the lower electrode
102 and the direction of the current flowing to the extended upper electrode 109 be large, for
example, in this modification. The angle of the direction of the current flowing in these parts is
about 90 °.
[0155]
As described above, in this modification, the lower electrode 102 in a portion where the
piezoelectric film 107 of the piezoelectric active portion 106 and the upper electrode 109 are
extended to the peripheral wall is removed to form the lower electrode film removed portion
115. Furthermore, the region facing the other openings 105 was covered with the lower
electrode 102. As a result, there is no end portion of the lower electrode 102 around the upper
electrode 109 constituting the piezoelectric active portion 106, and discharge is less likely to
occur. In the extended portion of the piezoelectric film 107 and the upper electrode 109, the
direction of the current flowing in the portion where the upper electrode 109 crosses the lower
electrode 102 and the direction of the current flowing in the extended upper electrode 109 do
not match. Therefore, the current flowing from the extended upper electrode 109 to the
piezoelectric active portion 106 is spread and dispersed at the intersection with the lower
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electrode 102. Therefore, dielectric breakdown of the piezoelectric film 107 due to electric field
concentration and the like can be prevented, and the durability and reliability of the element chip
can be improved.
[0156]
FIG. 35 is a schematic plan view of relevant parts showing the structure of the piezoelectric
element. Further, as shown in FIG. 35, a displacement suppression layer 124 for suppressing the
displacement of the piezoelectric active portion 106 is provided on the upper electrode 109 at
the boundary between the piezoelectric active portion 106 and the piezoelectric nonactive
portion 111. May be Thereby, the vibration at the end of the piezoelectric active portion 106 can
be suppressed. Furthermore, the occurrence of a crack or the like of the elastic film 108 due to
the driving of the piezoelectric active portion 106 can be prevented. Further, the displacement
suppressing layer 124 can be easily formed of, for example, the same material as the abovedescribed lead electrode 110.
[0157]
In this modification, the lower electrode 102 in the region corresponding to the piezoelectric film
107 and the upper electrode 109 is removed in a substantially rectangular shape to form the
lower electrode film removed portion 115, but the present invention is not limited to this. 36 (a)
and 36 (b) are principal part schematic plan views showing the structure of the piezoelectric
element. For example, as shown in FIG. 36A, the lower electrode film removing portion 115 may
be provided in a substantially circular or elliptical shape in a region facing the opening 105.
Further, in this case, the base end portions of the piezoelectric film 107 and the upper electrode
109 which are extended with a width smaller than that of the piezoelectric active portion 106
may be further removed to the inside of the piezoelectric active portion 106. As a result, the
angle between the direction of the current flowing to the portion where the upper electrode 109
crosses the lower electrode 102 and the direction of the current flowing to the extended upper
electrode 109 is increased, that is, the piezoelectric from the extended upper electrode 109 The
spreading direction of the current flowing into the body active portion 106 is increased, and the
electric field applied between the upper electrode 109 and the lower electrode 102 is further
dispersed.
[0158]
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Further, for example, as shown in FIG. 36B, the shape of the lower electrode film removing
portion 115 is made approximately semicircular, and the width of the longitudinal end of the
piezoelectric active portion 106 is gradually reduced. Furthermore, the lower electrode 102 and
the upper electrode 109 may cross each other at the arc portion of the lower electrode film
removing portion 115. Also with this configuration, the angle between the direction of the
current flowing to the portion where the upper electrode 109 crosses the lower electrode 102
and the direction of the current flowing to the extended upper electrode 109 becomes large.
Therefore, the electric field applied between the lower electrode 102 and the upper electrode
109 is dispersed as described above.
[0159]
As described above, the shapes of the lower electrode film removing portion 115 and the
extended portions of the piezoelectric film 107 and the upper electrode 109 are not particularly
limited, but the direction of the current flowing in the extended portion of the upper electrode
109 and the lower portion Preferably, the angle with the direction of the current flowing in the
portion crossing the electrode 102 is 5 ° to 180 °.
[0160]
(Modification 11) FIG. 37 is a schematic plan view of relevant parts showing the structure of the
piezoelectric element.
In this modification, as shown in FIG. 37, the lower electrode 102 is removed at substantially the
center in the longitudinal direction on the peripheral wall on both sides in the width direction of
the opening 105 to form a lower electrode film removed portion 115. The piezoelectric film 107
and the upper electrode 109 are extended from the substantially central portion in the
longitudinal direction of the piezoelectric active portion 106 to the peripheral wall above the
lower electrode film removing portion 115 to form a piezoelectric inactive portion 111. Further,
the upper electrode 109 extended on the peripheral wall is connected to the external wiring
through the lead electrode 110. Except this, it is the same as that of modification 10.
[0161]
As described above, by extending the piezoelectric film 107 and the upper electrode 109 from
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the central portion in the width direction of the opening 105, the driving loss of the piezoelectric
active portion 106 is suppressed and the rise of the vibration of the elastic film 108 is
accelerated. Can. Also, of course, the same effect as that of the modification 10 can be obtained.
[0162]
(Modification 12) FIG. 38 is a schematic plan view of relevant parts showing the structure of a
piezoelectric element. In this modification, as shown in FIG. 38, the piezoelectric non-active
portion 111 in which the piezoelectric film 107 and the upper electrode 109 of the piezoelectric
active portion 106 extend from both sides in the width direction of the opening 105 to the
peripheral wall is provided. Except for the above, the modification 11 is the same as the
modification 11.
[0163]
Even with such a configuration, the same effect as that of the eleventh modification can be
obtained. Further, since the piezoelectric film 107 and the upper electrode 109 are extended on
the peripheral wall from both sides of the opening 105, the drive loss of the piezoelectric active
portion 106 can be further suppressed, and the vibration characteristic of the elastic film 108 is
improved. It can be done.
[0164]
(Modification 13) FIG. 39 (a) is a schematic plan view of the main part showing the structure of
the piezoelectric element. 39 (b) and (c) are schematic side sectional views of the relevant part
showing the structure of the piezoelectric element. In this modification, as shown in FIG. 39, a
residual portion 125 formed of the same layer as the lower electrode 102 is provided on the
partition wall of the opening 105. In the present modification, the remaining portion 125 is
provided continuously in the longitudinal direction of the opening 105 with the lower electrode
102 of the piezoelectric active portion 106. That is, the lower electrode film removing portion
115 from which the lower electrode 102 is removed is provided in a region facing the boundary
between the opening 105 and the partition on both sides in the width direction. Thus, the
configuration is the same as that of the third embodiment except that the remaining portion 125
is formed in the region facing the partition wall.
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[0165]
Here, the distance h 1 between the end side surface of the lower electrode 102 in the width
direction and the end side surface of the remaining portion 125 in the width direction is
extended on the side surface and peripheral wall of the longitudinal end of the piezoelectric film
107 The distance h 2 until the lower electrode 102 becomes wider is preferably longer than the
film thickness of the piezoelectric film 107 and smaller than the width of the lower electrode
102.
[0166]
Further, the width of the residual portion 125 is preferably 50% or more of the width of the
partition wall, and more preferably 80% or more.
Furthermore, it is preferable that the lower electrode 102 or the remaining portion 125 be
formed in at least 50% or more of the plurality of openings 105 arranged in parallel and the
region facing the partition on both sides in the width direction.
[0167]
In this modification, the lower electrode 102 is removed in the form of narrow grooves along the
direction in which the openings 105 are arranged in the vicinity of the end of the opening 105
on the side where the piezoelectric film 107 and the upper electrode 109 extend. The lower
electrode film removing unit 115 is formed. The lower electrode film on the peripheral wall of
the opening 105 is a discontinuous lower electrode film 114 which is discontinuous with the
lower electrode 102 constituting the piezoelectric active portion 106. Then, the piezoelectric film
107 and the upper electrode 109 are extended on the discontinuous lower electrode film 114 to
form the piezoelectric non-active portion 111, and although not shown, the upper electrode 109
and the external wiring are near the end. And are connected.
[0168]
Also in such a configuration, the same effect as that of the third embodiment can be obtained.
Furthermore, in the present modification, the remaining portion 125 is provided in the region
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51
facing the partition walls on both sides in the width direction of the opening 105, preferably
under the above-described conditions. As a result, the area where the lower electrode 102 is
removed is extremely reduced. Therefore, even if the piezoelectric film 107 is formed on the
patterned lower electrode 102, the film thickness of the piezoelectric film 107 becomes
substantially uniform overall, and the film thickness of the piezoelectric film 107 becomes locally
small. Absent.
[0169]
Further, since the distance h 2 between the side surface of the longitudinal end of the
piezoelectric film 107 and the lower electrode 102 extended on the peripheral wall is relatively
narrow, the longitudinal end of the opening 105 is Even in the vicinity, the film thickness of the
piezoelectric film 107 becomes uniform. Thus, even when the piezoelectric film 107 in the
vicinity of the end on the side where the lower electrode 102 of the opening 105 is drawn is
etched by a nonselective etching method such as ion milling, the lower electrode 102 under the
piezoelectric film 107 Is not removed together and the film thickness does not decrease.
Therefore, the rigidity of the lower electrode 102 in the vicinity of the end of the opening 105 is
not reduced, and the durability is improved. Further, such an effect is particularly remarkable
when the piezoelectric film 107 is formed by a spin coating method such as a sol-gel method, and
in addition, it is formed by, for example, a MOD method (organic metal thermal decomposition
method). You may do it.
[0170]
(Modification 14) FIG. 40 is a schematic plan view of the main part showing the structure of the
piezoelectric element. In this modification, as shown in FIG. 40, the remaining portion 125
provided on the partition in the width direction of the opening 105 is continuous with the
discontinuous lower electrode film 114 instead of the lower electrode 102 constituting the
piezoelectric active portion 106. Except that it is provided in the same manner as the
modification 13.
[0171]
Even with such a configuration, the film thickness of the piezoelectric film 107 is not reduced,
and the same effect as that of the modification 13 can be obtained.
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[0172]
(Modification 15) FIG. 41 (a) is a schematic plan view of the main part showing the structure of
the piezoelectric element.
FIG. 41 (b) is a schematic side sectional view of the main part showing the structure of the
piezoelectric element. As shown in FIG. 41, in the present modification, the end portion of the
lower electrode 102 which is the boundary between the piezoelectric active portion 106 and the
piezoelectric inactive portion 111 moves from the piezoelectric active portion 106 toward the
lower electrode film 103 for wiring. The third embodiment is the same as the third embodiment
except that the film thickness gradually decreasing portion 126 in which the film thickness of the
lower electrode 102 gradually decreases is provided. Further, the shape of the gradually
decreasing film thickness portion 126 is not particularly limited, but for example, in the present
modification, it is an inclined surface in which the film thickness of the lower electrode 102 is
gradually reduced.
[0173]
As described above, in this modification, the film thickness taper portion 126 whose film
thickness gradually decreases toward the outside of the piezoelectric active portion 106 is
provided at the end portion of the lower electrode 102 which is the end of the piezoelectric
active portion 106. It was set up. Thereby, the piezoelectric film 107 is formed along the shape
on the lower electrode 102 including the gradually decreasing film thickness portion 126, and
the entire film thickness becomes substantially uniform. That is, the film thickness of the
piezoelectric film 107 at the end of the lower electrode 102 is not reduced, and the dielectric
breakdown due to the electric field concentration or the like of the piezoelectric film 107 near
the end of the piezoelectric active portion 106 is suppressed. Can.
[0174]
In this modification, although the film thickness taper part 126 was made into the slope which a
film thickness reduces gradually continuously, it is not limited to this. FIGS. 42 (a) and 42 (b) are
principal part schematic side sectional views showing the structure of the piezoelectric element.
For example, as shown in FIG. 42 (a), the film thickness gradually decreasing portion 126a may
be configured so that the film thickness is reduced gradually and the cross section has a
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substantially stepped shape. The method for forming such a gradually decreasing film thickness
portion 126a is not particularly limited, and, for example, the film thickness is in a region where
the resist is applied a plurality of times on the lower electrode 102 to become the gradually
decreasing film thickness portion 126a of the lower electrode 102 After forming the step-like
resist film substantially the same as the gradually decreasing portion 126a, the lower electrode
102 can be formed by patterning.
[0175]
Also, for example, as shown in FIG. 42 (b), the film thickness taper portion 126b may be
configured such that the cross section is formed by an inclined curved surface. The method for
forming such a gradually decreasing film thickness portion 126b is also not particularly limited,
and for example, a region on the elastic film 108 where the lower electrode 102 is not formed
and a region to become the gradual film thickness reduction portion 126b are covered with a
mask The lower electrode 102 is formed by film deposition. That is, the lower electrode 102 is
also formed in a part of the region covered by the mask, coming around from the gap of the
mask, and the cross section becomes the gradually decreasing film thickness portion 126b of the
inclined curved surface. Also, as a matter of course, as described above, after forming a resist film
having substantially the same shape as the gradually decreasing portion 126 b on the lower
electrode 102, the lower electrode 102 can be formed by patterning.
[0176]
(Modification 16) FIG. 43 (a) is a schematic plan view of the main part showing the structure of
the piezoelectric element. FIG. 43 (b) is a schematic side sectional view of the main part showing
the structure of the piezoelectric element.
[0177]
The present modification is an example in which an insulating film 127 made of an insulating
material is provided outside the lower electrode 102 in the longitudinal direction. That is, in this
modification, as shown in FIG. 43, the piezoelectric active portion 106 including the lower
electrode 102, the piezoelectric film 107, and the upper electrode 109 is formed on the elastic
film 108 in the region facing the opening 105. . An insulating film 127 having a thickness
substantially the same as that of the lower electrode 102, for example, is formed outside the end
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of the lower electrode 102 at the boundary between the piezoelectric active portion 106 and the
piezoelectric inactive portion 111. did. The material of the insulating film 127 is not particularly
limited, and may be an insulating material different from that of the elastic film 108, for example.
[0178]
Further, in the present modification, after the lower electrode 102 is patterned, the insulating
film 127 is formed on the outside of one end in the longitudinal direction. The piezoelectric film
107 and the upper electrode 109 were formed thereon and patterned to form the piezoelectric
active portion 106 and the piezoelectric inactive portion 111. Thus, the film thickness of the
piezoelectric film 107 is not reduced at the end of the lower electrode 102, and dielectric
breakdown due to electric field concentration or the like of the piezoelectric film 107 can be
prevented at this portion. Also in this configuration, of course, the same effects as those of the
above-described embodiment can be obtained.
[0179]
(Modification 17) FIG. 44 (a) is a schematic plan view of the essential part showing the structure
of the piezoelectric element. FIG. 44 (b) is a schematic side sectional view of the main part
showing the structure of the piezoelectric element. In this modification, as shown in FIG. 44, a
thick film portion 108 a is provided instead of the insulating film 127 outside the end portion of
the lower electrode 102 which is a boundary portion between the piezoelectric active portion
106 and the piezoelectric inactive portion 111. The modification 16 is the same as the
modification 16 except for the provision. The thick film portion 108 a is formed so that the film
thickness of the elastic film 108 is thicker than that of other portions, and for example, in the
present modification, it is thicker than the film thickness of the lower electrode 102.
[0180]
Further, in the present modification, after the elastic film 108 is patterned to form the thick film
portion 108a at a predetermined position, the piezoelectric film 107 and the upper electrode
109 are formed and patterned to form the piezoelectric active portion 106 and the piezoelectric
nonactive. The portion 111 was formed. As a result, the film thickness of the piezoelectric film
107 in the region corresponding to the end of the lower electrode 102 does not become thinner
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55
than the other portion, and dielectric breakdown due to electric field concentration of the
piezoelectric film 107 is formed in this portion. be able to. Also in this configuration, the same
effect as the third embodiment can be obtained.
[0181]
(Modification 18) FIG. 45 (a) is a schematic plan view of the essential part showing the structure
of the piezoelectric element. FIG. 45 (b) is a schematic side sectional view of the main part
showing the structure of the piezoelectric element. This modification is an example in which the
end of the upper electrode 109 is formed inside the end of the lower electrode 102, as shown in
FIG. An end of the upper electrode 109 is an end of the piezoelectric active portion 106. Also, for
example, in the present modification, the end of the piezoelectric film 107 is substantially at the
same position as the end of the lower electrode 102, and the piezoelectric film is also formed on
the lower electrode 102 that protrudes outward beyond the end of the upper electrode 109.
Reference numeral 107 is formed, and this portion is a piezoelectric non-active portion 111
which is not substantially driven.
[0182]
In this modification, the piezoelectric film 107 is not removed in the lower electrode film
removing portion 115 from which the lower electrode 102 between the lower electrode 102 and
the lower electrode film 103 for wiring is removed. It is left behind. Since the piezoelectric film
107 of the lower electrode film removing portion 115 functions as an insulating film, the lower
electrode 102 and the lead electrode 110 are insulated.
[0183]
As described above, in the present modification, the piezoelectric non-active portion 111 is
continuously provided by removing the upper electrode 109, for example, on the outside of the
lead-out end side of the lead electrode 110 of the piezoelectric active portion 106. did. Thereby,
the distance between the end of the upper electrode 109 which is the end of the piezoelectric
active portion 106 and the end of the lower electrode 102 can be increased. Therefore, even
when a voltage is applied to the piezoelectric active portion 106, the electric field strength at the
end of the piezoelectric active portion 106 does not increase, and dielectric breakdown or the
like of the piezoelectric film 107 can be prevented. In addition, since the thickness of the
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piezoelectric film 107 of the piezoelectric active portion 106 becomes uniform, the piezoelectric
characteristics are improved. Even with such a configuration, the same effect as that of the third
embodiment can be obtained.
[0184]
(Modification 19) In the first embodiment, after patterning a PZT film, heat treatment is
performed at 700 ° C. in an oxygen atmosphere to form the piezoelectric film 26. Not only this
but you may carry out at the next process. Heat treatment is performed to form the piezoelectric
film 26. At this time, treatment is performed under an oxygen atmosphere and an atmosphere of
100% water at a temperature of 600 ° C. to 700 ° C. and a pressure of 200 atm or less. The
heating step may be performed by heating and crystallizing the amorphous thin film, or a heat
treatment step may be provided after the heating step to perform the heat treatment step. When
the heat treatment is performed under these conditions, the amount of oxygen in the PZT film
can be increased. When the heating temperature exceeds 700 ° C., Pb is lost from the PZT film.
Also, when the pressure exceeds 200 atm, the hysteresis curve peculiar to the ferroelectric is not
observed. This degrades the performance of the PZT film. Therefore, when heat treatment is
performed on the crystallized PZT or PZT-based ceramic thin film in an atmosphere containing
water, the atmosphere water is 100%, the pressure of the atmosphere is 200 atm or less, and the
temperature is 700 °. It is desirable that it is C or less.
[0185]
In this modification, heat treatment may be performed in an atmosphere containing water after
crystal growth in a PZT thin film formed by sol-gel method, and of course, heat treatment may be
performed in an atmosphere containing water when crystal growth is performed. Also, the thin
film material is not limited to lead zirconate titanate (Pb (Zr, Ti) O 3: PZT), and other ceramic
materials, for example, lead lanthanum titanate ((Pb, La) TiO 3), lead zirconate Lanthanum ((Pb,
La) ZrO 3), Lead lanthanum zirconate titanate ((Pb, La) (Zr, Ti) O 3: PLZT), Magnesium niobate
zirconate titanate (Pb (Mg, Nb) ( The present invention may be applied to Zr, Ti) O 3: PMN-PZT),
strontium titanate, lithium niobate, zirconia, Y-1, ITO and the like. In addition to the sol-gel
method, an amorphous thin film may be formed by a MOD (Metallo-Organic Decomposition)
method, a sputtering method, or a vapor deposition method.
[0186]
(Other Modifications) Although the embodiment and modifications have been described above,
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the basic configuration of the ultrasonic transducer element chip is not limited to the one
described above.
[0187]
For example, in the third embodiment, the end of the lower electrode 102 is used as the end of
the piezoelectric active portion 106, and the piezoelectric film 107 and the upper electrode 109
are extended to the outer side to make the piezoelectric inactive. Although the portion 111 is
provided to prevent destruction of the end of the piezoelectric active portion 106, patterning of
the piezoelectric active layer 106 and the upper electrode 109 in the opening 105 is performed
at the other end. It is an end.
Such an end portion may cause peeling or the like of the piezoelectric film 107 and the upper
electrode 109. For example, the end portion is fixed by an adhesive or the like, or the end portion
of the piezoelectric active portion 106 is protected by covering the end portion with the
piezoelectric film 107 of the piezoelectric element 104 with a discontinuous piezoelectric film or
the like. Durability may be improved.
[0188]
Of course, it is needless to say that the above-described embodiments and modifications can be
combined as appropriate to achieve further effects.
[0189]
Moreover, each embodiment and modification which were mentioned above made the thin film
type ultrasonic transducer element chip | tip which can be manufactured by applying a film
formation and a lithography process to an example.
Of course, it is not limited to this. For example, the openings 45 are formed by laminating
substrates. Or what forms a piezoelectric material film by sticking a green sheet or screen
printing etc. Alternatively, the structure of various manufacturing methods such as one in which
a piezoelectric film is formed by crystal growth such as a hydrothermal method can be adopted
for an ultrasonic transducer element chip.
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[0190]
Thus, the present embodiment can be applied to ultrasonic transducer element chips of various
structures, as long as the purpose of the embodiment is not violated.
[0191]
16: housing, 17: element chip as an ultrasonic transducer element chip, 24: lower electrode as a
metal film, 24b: adhesion film, 26: piezoelectric film as a piezoelectric thin film, 43: vibrating
film.
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