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JP2012029290

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DESCRIPTION JP2012029290
The present invention relates to a MEMS and / or NEMS type or cMUT type device, for example
for generating acoustic energy. The invention relates to a device for generating or restoring
acoustic energy, comprising at least one wall comprising at least one movable or deformable wall
(25) and a cavity from the outside air. At least one first deformable cavity (20) formed in the first
substrate, defined by means for communicating with it, for receiving external air,-displacement in
the plane of said sensor or Means (24, 24 ', 24, 24') for causing deformation or for recovering
energy resulting from displacement or deformation of the movable or deformable wall in the
plane of the sensor And [Selected figure] Figure 2B
MEMS type pressure pulse generator
[0001]
The present invention relates to a pressure pulse generator of MEMS type and / or NEMS type.
[0002]
This makes it possible to produce MEMS loudspeakers, digital MEMS loudspeakers, and cMUTs
("capacitive micromachined ultrasonic transducers").
In fact, the generation of pressure pulses is mainly concerned with two applications: loudspeaker
and cMUT.
04-05-2019
1
[0003]
There are two approaches to producing MEMS loudspeakers, one is the traditional approach of
the analog loudspeaker type and the other is the digital loudspeaker type approach.
[0004]
Analog loudspeakers are formed by a membrane which operates by electromagnetic, electrostatic
or piezoelectric means at the frequency of the sound to be restored.
The volume restored is proportional to the displacement amplitude of the membrane.
[0005]
Some are made in MEMS form, for example, see the article by Neumann J J et al., 2001, "CMOSMEMS membrane for audio frequency actuation" IEEE Int. Proc. MEMS 2001-, pages 236-9
as described.
[0006]
FIG. 1A shows the structure of the generator, for which J. Rehder et al., "Balance membrane
micromachined loudspeakers for hearing instrument application" -J. Micromech.
Microeng. 11, 2001, pages 334-338. The generator comprises means for forming a
substrate 1 made of soft magnetic material, an electrodeposition core, means 3 for forming
electrical contacts, a coil 4 and a permanent magnet 5. The generated sound exits through the
outlet 6. Reference 7 indicates a film made of non-soft magnetic material and reference 8
indicates a means for forming a spacer.
[0007]
However, the actuation amplitude of these MEMS films is very limited. As a result, the volume is
also very low as a whole.
04-05-2019
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[0008]
Furthermore, given the dimensions of these MEMS components, the bass recovery (the sound
level is directly proportional to the frequency, thus requiring a larger displacement amplitude to
compensate for the decrease in sound level caused by the frequency decrease) Is virtually
impossible at acceptable levels.
[0009]
Finally, the large response non-linearity of the MEMS film (embedded around) becomes quite
large once it exceeds the amplitude around the film thickness.
This results in significant distortion even at low acoustic levels.
[0010]
The second approach, traditionally referred to as "digital loudspeaker", is far from the traditional
and individually addressed and generates sound pressure pulses, respectively, as shown in FIG.
1B, membrane 101 , 102, 103,. . . The approach is to use a 10 n array 10. The sound is then
reconstructed by applying these pressure "bits". The amplitude of the oscillation is then
determined by the number of simultaneously addressed membranes, and the frequency to be
recovered is determined by varying the amplitude as a function of time.
[0011]
Only a few papers deal with this type of loudspeaker. The only exemplary embodiment of MEMS
is described by Brett M. et al. Diamond et al., "Digital Sound Reconstruction Using Arrays of
Cmos-Mems Microspeakers", TRANSDUCTERS '03-The 12th International Conference on Solid
State Sensors, Actuators and Microsystems. Boston, June 8-12, 2003. It uses electrostatic
actuation.
[0012]
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In the case of digital loudspeakers, generate pressure and vacuum pulses with sufficient
amplitude and possibly the same strength and shape (rise and fall times of the membrane) to
restore good quality sound; It should be possible to control the rising and falling edges of the
membrane for both pulsed and vacuum pulses.
[0013]
However, in the case of the device proposed in the above-cited document, the suspended
membrane is activated by the empty electrostatic means.
[0014]
This film can only generate pressure (or depression or partial vacuum) pulses with
electrostatically actuated in a single direction.
In addition, simple mechanical relaxation of the membrane is used to generate reverse
depression or partial vacuum (or pressure) pulses.
With this arrangement it is virtually impossible to generate the same pressure or negative
pressure or incomplete vacuum pulse.
[0015]
Another problem is that the use of electrostatic actuation due to air gap changes involves the
non-linear deformation amplitude of the film changing as a function of the applied voltage. This
makes it very difficult to control rising and falling edges. In the case of pulses generated by
mechanical relaxation of the membrane, the return of the membrane to equilibrium depends only
on its mechanical properties. Thus, the deformation as a function of time can not be controlled
electrically. This also makes it impossible to dampen vibration bounces which substantially affect
the acoustic properties of the device.
[0016]
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Finally, in the use of electrostatic actuation with air gap change, it is assumed that the
deformation amplitude greater than 1/3 of the air gap is not exceeded in order to avoid "pull-in".
The "pull-in" voltage is the voltage above which the electrostatic force is large enough to cause
the system to become unstable. There is then the risk of adhesion of the two armatures of the
electrostatic actuator capacitance. This results in a large limitation of the accessible deformation
amplitude for a given maximum voltage (amplitude / air gap and air gap / high voltage
compromise).
[0017]
cMUT is described, for example, in the article by Yongli Huanga et al., "Capacitive micromachined
ultrasonic transducers (CMUTs) with isolation posts", Ultrasonics, Vol. 48, No. 1, March 2008,
pages 74-81. .
[0018]
cMUTs in particular have very limited pressure levels.
This limitation arises because the accessible amplitude for each of the cMUT membranes is low.
This maximum amplitude is a compromise between the value of the air gap between the
membrane and the excitation electrode (thus 'pull-in'), the highest permissible voltage (less than
100 V for safety reasons), and the breakdown voltage of the insulating oxide It is derived from.
[0019]
The reliability problem of this type of device is due to dielectric charging, as already mentioned
in the above cited paper. It can also be said that it is difficult to generate different frequency
pressures on the same component when using these cMUTs in conjunction with imaging (> 10
MHz) and therapy (<5 MHz). In this case it is in fact assumed that having two very different air
gap thicknesses can maintain a comparable supply voltage for the two frequencies. In this aspect,
current technology is very complicated.
[0020]
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5
Neumann J J et al., 2001, "CMOS-MEMS membrane for audio frequency actuation" IEEE Int.
Proc. MEMS 2001-, pages 236-9 J. Rehder et al., "Balance membrane micromachined
loudspeakers for hearing instrument application" -J. Micromech. Microeng. 11, 2001,
pages 334-338. Diamond et al., "Digital Sound Reconstruction Using Arrays of Cmos-Mems
Microspeakers", TRANSDUCTERS '03-The 12th International Conference on Solid State Sensors,
Actuators and Microsystems. Boston, June 8-12, 2003 "Capacitive micromachined ultrasonic
transducers (CMUTs) with isolation posts", Ultrasonics, Vol. 48, No. 1, March 2008, pp. 74-81,
Yongli Huanga et al. The paper "Time and frequency response of two-arm micromachined
thermal actuators", R Hickey et al., 2003, J. Org. Micromech. Microeng. 13 to 40 pages
[0021]
The invention relates first of all to a MEMS and / or NEMS type or cMUT type device, for example
for generating acoustic energy, in a first substrate, referred to as the plane of the sensor At least
one first deformable cavity formed by at least one movable or deformable wall or membrane, and
at least one pressure or negative pressure or imperfection in ambient air A cavity defined by
means formed in the first cavity or by means for communicating the first cavity to the
atmosphere to transfer a vacuum pulse; said movable or deformable It comprises a wall or a
membrane, in the plane of the sensor, means for causing displacement or deformation.
[0022]
Thus, the invention relates to a generator structure of, for example, MEMS type and / or NEMS
type, the movable or deformable walls or membranes being as in the structures known from the
state of the art , Move in the plane of the substrate but do not move out of the plane.
[0023]
According to the invention, for example, capacitive or thermally activated actuation or excitation
moieties are uncorrelated from movable or deformable walls or membranes.
Thus, it is possible to optimize these two parts individually.
Thus, according to the invention, it is possible to implement two or more device structures each
having an actuator adapted to the stiffness of its movable or deformable wall.
04-05-2019
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[0024]
The actuation means can be used to actuate displacement or deformation of the movable or
deformable wall or membrane in both directions (pressure and vacuum).
[0025]
The device according to the invention may also comprise at least one secondary cavity, or buffer
cavity, in partial communication with the first cavity.
[0026]
Regardless of the pressure in the first cavity and the position of the movable or deformable wall,
the first cavity is not in "direct" communication with the second cavity, but "indirect"
communication is: For example, again via one or more spaces (“air gaps”), for example,
between the first substrate and the second substrate and / or between the first substrate and the
third substrate. Nevertheless, at some edges of the wall or of the deformable membrane.
This second cavity makes it possible to prevent excessive damping of the movement or
displacement of the pressure generating means in the plane of the sensor when the wall (or
membrane) is activated.
More specifically, the "air gap" may be a small space between the movable part and the
stationary part. This is, for example, arranged between the substrate and the movable or
deformable part, or between the movable or deformable part and the upper substrate. Apart from
its impedance loss function, this space allows the movable or alterable part to move in a plane.
[0027]
Again, this second cavity forms what is referred to as "back-volume" and can be optimized
separately from the part forming the actuation or excitation means. Because of this second cavity,
it is possible to move or deform the wall or deformable wall by limiting the gas compression
effect in this "back chamber volume," the compression that will limit the effectiveness of the
pressure generator. It is possible to limit the damping of the membrane. Its purpose is, in fact, to
generate excessive pressure (or negative pressure or partial vacuum) in the first cavity, but not
outside that cavity (in particular not in the "back chamber volume") It is.
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[0028]
The at least one secondary cavity can be formed in the plane of the second substrate different
from the first substrate or can be formed in the plane of the first substrate.
[0029]
Where the secondary cavity is formed in the plane of the second substrate different from the first
substrate, the second substrate means for transmitting at least one pressure or vacuum pulse,
and / or the first Means may also be provided for communicating one of the cavities with the
outside air, in other words for transmitting the second cavity and at least one pressure or
vacuum pulse to the outside air, or for connecting the first cavity to the outside air. Can be
formed in the same second substrate, which can be assembled with the first substrate, in which
case this is preferably closed and the closing operation can be performed by a membrane, -Or the
second substrate can be arranged on one side of the first substrate, the third substrate being
arranged on the opposite side of the first substrate, this third substrate being the first one
Comprising means for transmitting the means and / or at least one pressure or negative pressure
or partial vacuum pulse induced in the first cavity for communicating the cavity to the outside air
to the outside air.
In other words, the second substrate is disposed on one side of the first substrate and the third
substrate is disposed on the opposite side of the first substrate, the third substrate being at least
one pressure or Means are provided for transmitting a negative pressure or partial vacuum pulse
or for connecting the first cavity to the ambient air. The first substrate can then be disposed
between the second substrate and the third substrate.
[0030]
At least the second cavity may be open or closed, and it may be formed on the upper or lower
side of the device, but not on the same side as the first cavity, Or not in communication with the
outside air. If closed, the closing operation can be performed by the flexible membrane. When
this second cavity is closed, its volume is preferably sufficiently large to fully play the role of
"back chamber volume" (typically the volume is that of the volume of the first cavity 10 times
larger). In this case, the second (closed) cavity may be disposed on one side or the other side of a
first cavity or a first substrate on which the first cavity is formed.
04-05-2019
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[0031]
The invention makes it possible to monitor the rising and falling edges of movable or deformable
walls or membranes for both pressure and vacuum pulses.
[0032]
The actuation means may comprise capacitive or thermally activated means, for example by
means of bimorph or asymmetric effects.
[0033]
The present invention solves the problem of deformation amplitudes of non-linear membranes,
which vary as a function of applied voltage, when actuation is performed electrostatically by
surface changes or, in the case of actuation, by thermal effects.
This also contributes to the effective monitoring of the rising and falling edges of the respective
pressure or negative pressure or incomplete vacuum pulse.
[0034]
Capacitive means being the actuating means makes it possible to have good response linearity
(e.g. measured by the ratio of the voltage applied to the actuating means to the displacement
amplitude of the membrane) and thus the cavity The shape of the pressure pulse induced in can
be easily monitored.
[0035]
The capacitive means comprises a first comb which itself is movable in the plane of the sensor
and a second comb which is stationary, the teeth of the first comb alternating with the teeth of
the second comb At least one first set of electrostatic combs aligned and means for applying an
activation voltage to move the moveable comb relative to the stationary comb may be provided.
[0036]
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9
The device according to the invention may comprise a first activation means and a second
activation means arranged on either side of the first deformable cavity in the plane of the first
substrate. .
With these two sets of means it is possible to actuate the movable or deformable wall in two
opposite directions.
[0037]
In another embodiment of the invention, the means for causing displacement or deformation of
the movable or deformable wall generate: at least a first force in a first direction substantially
perpendicular to said wall Means for generating at least a second force in a second direction
substantially perpendicular to the first direction,-along said first direction with said second force.
And means for converting into force.
[0038]
In other words, the device according to the invention can comprise a plurality of actuation
assemblies arranged in the plane of the device around the deformable cavity.
Thus, according to a more complicated scheme, for example, movable or deformed by the
actuating assembly operating in compression of the deformable cavity while the other actuating
assembly operates under negative pressure or partial vacuum of the deformable cavity It is
possible to achieve possible wall activation.
[0039]
Thus, for capacitive operation, the device according to the invention is a second set of capacitive
combs, the first set of capacitive combs and the second set of capacitive combs being the first A
second set of capacitive combs comprising combs disposed on either side of the first deformable
cavity in the plane of the substrate (100) of the respective type, each of which can move in the
first direction And-at least a third set of capacitive combs, also movable in one of the planes of
the first substrate, capable of moving in a direction perpendicular to the first direction. Can.
[0040]
The device according to the invention may comprise a plurality of first deformable cavities, at
04-05-2019
10
least two of the cavities having shared actuation means.
[0041]
In ambient air, the means for transmitting at least one pressure or negative pressure or
incomplete vacuum pulse generated in the first cavity, or for causing the first cavity to
communicate with the ambient air, can for example be each deformable A single opening for
each deformable cavity located on the opposite side of the cavity, or a membrane located on or
opposite to the deformable cavity.
[0042]
According to a preferred embodiment, the at least one movable or deformable wall comprises
two side ends and is embedded or fixed at the two side ends.
Alternatively, it is rigid and is held by the deformable elements at its two side ends.
[0043]
The device according to the invention may also comprise means for forming an electrical contact
on the first side (referred to as the front side) or on the second side (referred to as the back side).
[0044]
The invention also relates to a method for fabricating a MEMS and / or NEMS type device, for
example for generating acoustic energy, which is defined by: at least one movable or deformable
wall Forming at least one first deformable cavity for receiving external air in a first substrate
defining a plane, referred to as a plane of the device, and-in the plane of the device Producing
means for causing displacement or deformation of said movable or deformable wall,-at least one
pressure or negative pressure or incomplete vacuum pulse generated in the first cavity in the
open air And D. making means for transmitting or for communicating the first cavity with the
outside air.
[0045]
The method according to the invention comprises, in partial communication with the first cavity,
at least one secondary cavity, referred to as "back chamber volume", or a buffer cavity, at least
04-05-2019
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partly in the second substrate, It may also include forming.
[0046]
At least one secondary cavity may be formed in the plane of the second substrate, which is
different from the first substrate, as already described above.
[0047]
The first substrate and the second substrate can be assembled through the dielectric layer to
form an SOI substrate.
[0048]
The method according to the invention can include assembling a first substrate with a third
substrate.
At least one pressure or negative pressure or partial vacuum pulse generated in the first cavity
may be transmitted to the atmosphere or means may be built therein for communicating the first
cavity with the atmosphere. .
[0049]
Preferably, the excitation means (or detection means) are at least partially formed in the first
substrate.
[0050]
The invention makes it possible to produce an original loudspeaker structure, or a digital
loudspeaker, or a cMUT structure, in this case an actuator means for generating pressure pulses
(or "speaklets") No longer move outside the plane of the substrate, but move in the plane.
There are many advantages to this configuration, the most important of which is the ability to
generate both pressure and negative pressure or incomplete vacuum pulses (for loudspeakers),
pressure or negative pressure or no pressure. Similar means to generate a full vacuum can be
04-05-2019
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used, which can have the same pressure or negative pressure or partial vacuum level, or can
generate high pressure levels (for cMUT) .
[0051]
The invention has several other advantages, for example: The pressure generated in the cavity
can displace the entire structure (not true for embedded membranes).
In fact, in the state of the art, pressure is generated by a membrane which is embedded all
around.
In the vicinity of this embodiment, the membrane does not in fact deform, and thus it is not
practically involved in the generation of pressure.
In the present invention, the beam or wall is only embedded at its ends.
The larger part of this deformable element consequently contributes to the generation of
pressure.
Therefore, the effect can be obtained while having the same film surface.
Thus, with the present invention it is possible to increase the pressure pulse generation effect,the present invention obviates the risk of "pull-in".
In the case of electrostatic excitation due to surface changes, the amount of displacement of the
wall is proportional to the voltage between the armatures of the capacitive comb.
Non-linear effects that can destabilize the system and cause structural adhesion and / or shorting
of the electrostatic actuator are prevented by the present invention.
04-05-2019
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[0052]
FIG. 1 illustrates aspects of prior art devices. FIG. 1 illustrates aspects of prior art devices. FIG. 6
shows various embodiments of the device according to the invention using a capacitive actuation
means. FIG. 6 shows various embodiments of the device according to the invention using a
capacitive actuation means. FIG. 6 shows various embodiments of the device according to the
invention using a capacitive actuation means. FIG. 6 shows various embodiments of the device
according to the invention using a capacitive actuation means. FIG. 6 shows various
embodiments of the device according to the invention using a capacitive actuation means. FIG. 6
shows various embodiments of the device according to the invention using a capacitive actuation
means. FIG. 7 is a top view of another example of a device according to the invention, with
several actuation means placed around a deformable cavity. FIG. 7 is a top view of another
example of a device according to the invention using a thermally activated actuation means. FIG.
7 is a side cross sectional view of another example of a device according to the invention with
several parallel cavities. FIG. 7 is a top view of another example of a device according to the
invention with several parallel cavities. Fig. 1 shows an example of an embodiment of a device
according to the invention. Fig. 1 shows an example of an embodiment of a device according to
the invention. Fig. 1 shows an example of an embodiment of a device according to the invention.
Fig. 1 shows an example of an embodiment of a device according to the invention. Fig. 1 shows
an example of an embodiment of a device according to the invention. Fig. 1 shows an example of
an embodiment of a device according to the invention. Fig. 1 shows an example of an
embodiment of a device according to the invention. FIG. 7 shows the steps of an alternative form
of another method for fabricating a device according to the invention. FIG. 7 shows the steps of
an alternative form of another method for fabricating a device according to the invention. FIG. 7
shows the steps of an alternative form of another method for fabricating a device according to
the invention. FIG. 7 is a top view of another embodiment of a device according to the present
invention. FIG. 7 is a top view of another embodiment of a device according to the present
invention. FIG. 6 shows an alternative form of the secondary cavity (or “back chamber
volume”) of the device according to the invention. FIG. 6 shows an alternative form of the
secondary cavity (or “back chamber volume”) of the device according to the invention.
[0053]
A first example of a structure according to the invention is shown in FIG. 2A, which is a crosssectional view along a plane and its outline AA 'is shown in FIG. 2B (top view). With this structure
it is possible to generate pressure or negative pressure or an incomplete vacuum pulse.
04-05-2019
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[0054]
Hereinafter, when referring to "substrate" 100, 101, 102, this may be understood as a "layer". As
a result, for these three elements, both of these terms can be used interchangeably.
[0055]
The structure according to the invention can be formed in two or three substrates 100, 101, 102
(in the case of FIG. 2A using three substrates) stacked and assembled together, the substrate 100
being the substrate 101 And the substrate 102. Each of the substrates 100, 102 has a thickness,
for example, in the range of a few μm to a few tens of μm, for example 1 μm or 5 μm to 10
μm or 50 μm. The substrate 101 has a thickness substantially close to, for example, several
tens of μm to several hundreds of μm, for example, in the range of 100 μm or 500 to 1000
μm, for example 750 μm. These dimensions can be used for all of the devices described below.
[0056]
Each of these substrates extends in a plane xy, the z-axis being perpendicular to each of the x, yaxes. Is the thickness of each substrate measured along this z-axis small in some cases before the
lateral extensions of the device, ie before the dimensions p and l of the device measured in the
plane xy Or very small, where p (measured along the x-axis) is, for example, in the range of 100
μm to 1 mm, and l (measured along the y-axis) is, for example, several hundred micro In the
order of meters, for example, in the range of 100 μm to 500 μm or 1 mm. The substrates can
each be made of semiconductor material (e.g. made of silicon or SiGe). These are attached to the
interface of the two substrates, except within the zone of mobility as described below, via the
adhesion zone, for example via one or more layers which are favorable to adhesion, such as a
layer of silicon oxide. Connected to each other. Hereinafter, the plane xy is referred to as the
plane of the device. This structure is found in the other embodiments described below. These
aspects of the invention may be used for all of the devices described below.
[0057]
From now on, the lower part or lower part of the device is the part facing the substrate 101 and
the upper part or upper part of the device is the opposite part facing the substrate 102.
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[0058]
The device initially comprises a cavity 20 formed in the substrate 100 with an opening in the
upper part.
[0059]
The opening 21 communicates with the opening of the substrate 100 and is also formed in the
substrate 102.
This makes it possible to transfer the pressure or the negative pressure or the partial vacuum
pulse generated in the cavity 20 to the ambient air.
Alternatively (an example of which will be shown below), this opening comprises a plurality of
orifices forming a grid, for example to limit the entry of foreign substances such as dust into the
cavity 20. Thus, it can also act as a filter. Alternatively, the cavity is closed by a flexible
membrane, such as the membrane 281 shown in FIG. 7A.
[0060]
In the plane of the substrate 100, the cavity 20 is defined by the sidewalls 23, 231, 232, 25 of
which some (the walls 23, 231, 232) are stationary and at least one of the rest (the Here the wall
or membrane 25) is movable or deformable in the plane xy of the device. In the example shown
in FIGS. 2A and 2B, the cavity 20 is rectangular in the plane of the device, but can be other
shapes as well. A structure without the wall 23 'of FIG. 2B through which the arm 40 passes can
also be formed in the context of the present invention. The movable wall or membrane 25 is
displaced or deformed in the plane xy under the influence of the actuation means 24 whose
embodiments are described below. In the example shown, the end of the movable wall 25 is fixed
to the two stationary walls 231, 232 and thus the arm 40 through one of the stationary walls 23
'. Via the influence of the actuating means, it is the deformation here of the movable wall.
[0061]
Thus, the wall here is of the “embedded-embedded” type, ie both of its side ends are embedded
04-05-2019
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in the stationary part of the device. This wall may have approximately the following geometrical
properties: -Height (measured along the z-axis): substantially equal to the thickness of the
substrate 100, and thus in the range of tens of microns to hundreds of microns, but in some
embodiments a few microns To several tens of μm (for example, in the range of 5 μm to 50
μm). Width (measured along the y-axis): for example in the range 0.5 μm to 10 μm, this width
being small enough for the wall 25 to have the desired sensitivity to actuation under the
influence of the actuation means 24 . Length (measured along the x-axis): for example in the
range from 100 μm to 1 mm.
[0062]
Alternatively, the movable wall may be of the type shown below with respect to FIGS. 4A and 4B.
There, it comprises a rigid main part that moves under the influence of pressure, at least one or
two side parts 253, 255 each forming a "spring", which can be deformed with the stationary part
Connect the parts.
[0063]
In this embodiment, as in the following embodiments, using one or the other of the different
types of deformable walls or membranes just presented or presented in the continuation of this
text It is possible.
[0064]
Alternatively, several cavities can be formed in the structure 100, an example of which will be
shown later.
[0065]
Thus, the actuation means 24 are stationary or connected or, more generally, associated with
these movable walls, this means here in the form of electrostatic excitation means, more
particularly It takes the form of a capacitive comb.
[0066]
These capacitive combs are arranged according to a specific configuration, which will be
described below, the movable part of the comb being displaced along the y-axis and the direction
04-05-2019
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of extension of the teeth of the comb.
However, other configurations are possible, such as the configuration of FIG. 10, where the comb
teeth extension direction is along the x-axis (and the portion of the comb moves along the y-axis).
[0067]
Here, electrostatic excitation by surface change is taken up, but alternatively, electrostatic
excitation by air gap change can also be performed.
An example of this alternative form is shown in FIG. 11, in which the distribution of the air gap
takes place, for example, in 1/3 to 2/3, and the air gap between the two teeth of a stationary
comb Is d, and if idle, the movable comb teeth are between the two teeth of the stationary comb,
and the two teeth of the movable comb and the stationary comb The distance between one of the
two is d1 (equal to about 1/3 of the distance d) and the same tooth of the movable comb and the
other of these two teeth of the stationary comb The distance between is d2 (equal to about 2/3 of
the distance d).
The comb teeth in this case are perpendicular to the direction of displacement of the deformable
membrane or piston. Alternatively, this means may also include means operated by thermal
effects, an example of which is further described below.
[0068]
Regardless of the nature of the actuation means, it can be actuated by at least two sets of
actuation means arranged on either side of the cavity, as will be explained later. This is in
particular when the cavity 20 comprises two movable or deformable walls, or activating the
movable wall in either direction (ie generating pressure or negative pressure or imperfect
vacuum waves If you want to be able to The means 24 can be activated by changing physical
parameters, thereby causing a change in the volume of the cavity 20. Thus, this may be
associated with means 26 which make it possible to cause a change in this physical parameter,
here a voltage change resulting in a change in capacity, and thus the relative movement of the
two combs. This results in a corresponding displacement or deformation of the wall 25 or a
04-05-2019
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corresponding change of the volume 20.
[0069]
In this example, cavities 20 and means 24 are formed in the intermediate substrate 100, as in the
following example.
[0070]
The device according to the invention comprises a stationary part, ie a part whose position does
not develop under the influence of the actuating means, and a movable part, ie a part whose
position develops or is modified under the influence of the actuating means. Prepare.
The movable part is connected to the stationary part. The elasticity of the means (e.g. one or
more arms such as the arms 56, 58) or the movable or deformable wall 25 itself or the end 253,
255 of the wall (in the case of FIG. 4B) It is possible to allow the means to be returned to the
initial position relative to the wall when it returns to its initial state (or is no longer supplied with
power).
[0071]
The cavity 20 is subject to the displacement provided by the actuation means. One side of the
membrane or wall 25 is in contact with the "average" ambient pressure, eg atmospheric pressure.
To that end, the device may comprise at least one lower secondary cavity 28, 28 'formed in the
lower substrate 101. This cavity is open under the device. Alternatively, as will be described in
more detail later, a closed secondary cavity is formed above or below the device, preferably then
having a sufficient volume (the volume being at least several times the volume of cavity 20, For
example, at least five times its volume, for example ten times the volume of its cavity 20),
movable or deformable wall or membrane under the influence of the actuation means without
causing excessive damping. It is possible to move with
[0072]
According to yet another alternative form, the one or more secondary cavities 28, 28 'may be
04-05-2019
19
open (or closed) at the sides, eg at least one of this type A cavity is formed in the intermediate
substrate 100. Examples of side cavities are shown in FIGS. 2C, 12A-12B.
[0073]
Regardless of the shape and position within the device, this secondary cavity is also indicated by
the expression "back chamber volume". This is located in a different plane or substrate 101 (or
102) than the cavities 20 and means 24 in FIGS. 2A and 2B and in most of the other illustrated
embodiments. However, in the case of FIGS. 2C, 16A-16B, this is formed in the same substrate as
the main cavity 20.
[0074]
In the present example, this secondary cavity is offset in its own plane with respect to the cavity
20. In other words, there is no intersection between the projection and the contour of the
secondary cavity 28 in the plane of the substrate 101 of the main cavity 20.
[0075]
However, since a relatively small space is maintained between the upper portion 250 and / or the
lower portion 25'0 of the wall 25 and the upper surface 101 'of the substrate 101 and the lower
surface 102' of the substrate 102, these two cavities There is also communication between, or
more generally, between the main cavity and at least one of several secondary cavities.
Therefore, there is a leak between the two cavities 20 and 28 reliably. In this way, and regardless
of the state or position of the activation means and the position of the movable wall, the cavity
20 communicating with the outside air through the opening 21 is a part of the secondary cavity
28, 28 '. It communicates with any one. One or more of these secondary cavities can reduce the
compression effect of the gas upon displacement of the membrane, since this tends to reduce the
sensitivity of the device Is advantageous. These cavities can also be referred to as damping
cavities.
[0076]
Thus, the deformable cavity 20 and the one or more secondary or damping cavities 28, 28 'are in
partial communication, at least partially separated by the wall or membrane 25, and are
04-05-2019
20
themselves under the influence of the actuating means Can be moved (or deformed) in the plane
of the substrate.
[0077]
The device also comprises contact zones 30, 30 ', 32.
These contact zones make it possible to connect the means 26, 26 'to activate the actuating
means and are thus adapted to cause a negative pressure or a partial vacuum or pressure in the
cavity 20, which is preferred. It becomes possible to apply a voltage change. Here, in the example
of the actuation means in the form of an electrostatic comb, the voltage change by the means 26,
26 'causes a displacement of the comb.
[0078]
In the example shown, the contacts are placed on the front of the device, ie it is possible to access
them through the openings formed in the substrate 102 or form the contacts in the openings can
do. However, it is also possible to form the contacts on the rear side, as shown in the following
example.
[0079]
We will now give a slightly more detailed description of the construction of the capacitive comb
24 used as actuation means for the above presented embodiments.
[0080]
The first comb is connected to the moveable wall 25 via an arm 40 extending substantially along
the y-axis.
When the movable comb 24 is moved in the direction shown in FIG. 2B (and indeed also along
the direction y) by the variation of the voltage V applied by the means 26, the wall 25 Pulled by
40, the arm 40 itself is pulled by the comb. It should be noted here that this component is used
04-05-2019
21
as an actuator and not as a sensor. Thus, the supply voltage of the actuator is adapted to prevent
excessive displacement of the wall or membrane 25. However, it is possible to provide a stop 43,
43 'to limit the displacement of this wall or membrane 25 or to absorb the impact on the device,
or alternatively to perform the same function. It is also possible to use 'as a stopper.
[0081]
The comb 24 has several teeth parallel to each other, each tooth extending in the plane zy. These
teeth are formed in the substrate 100. These are all fixed to the arm 42, arranged substantially
perpendicular to the plane zy, and thus rather along the x-axis and perpendicular to the arm 40.
Alternative forms of void change capacitive actuation will be described later. The stationary part
52 of the device, also made in the form of an arm substantially parallel to the arm 42, is also
fixed or connected to the comb 24 'and the comb itself also has a row of teeth parallel to each
other And each tooth is also located in the plane of the direction zy. These teeth of the stationary
part are also formed in the substrate 100.
[0082]
The two rows of teeth of the comb 24, 24 'are formed by a portion of each tooth of the comb 24
(except for the teeth potentially located at the end of one row of teeth) of two adjacent teeth of
the comb 24'. They are arranged alternately in the form of being placed between them. A portion
of each tooth of the comb 24 '(except for the teeth potentially located at the end of a row of
teeth) is then placed between two adjacent teeth of the comb 24'.
[0083]
Each tooth can have a thickness measured along the x-axis ranging from 2 μm or 5 μm to 10
μm or 100 μm. Two adjacent teeth of the same comb are separated by a distance ranging from
0.5 μm or 1 μm to 3 μm or 10 μm.
[0084]
The teeth of the two combs are electrically conductive.
04-05-2019
22
[0085]
When the device is idle, and a preferred potential difference is established between the two rows
of teeth, a set of parallel plate capacitors is formed.
Varying the voltage V causes the teeth of movable comb 24 to move relative to the teeth of
stationary comb 24 ', for example, in the direction indicated by the arrow in FIG. 2B, and thus the
arm The displacement 40 causes displacement or deformation of the wall 25.
[0086]
The embodiment of FIG. 2B is a side of the frame in which the arm 42 actually comprises three
other arms or sides 44, 46, 48 which surround the walls 23, 231, 232, 25 which define the
cavity 20. It is shown to constitute one of the sides. Therefore, it is the entire frame that is moved
when the movable comb 24 is displaced due to the change of the voltage V. The side or arm 48
on the opposite side of the arm 42 can also be connected to the movable comb 241 by means of
an arm 40 'which is oriented along the y axis, so this movable comb 241 is also When the voltage
V ′ applied to the movable comb 241 changes, it can be displaced, for example, in the direction
opposite to the direction of the arm 40. Combs 241 are also formed in the substrate 100. The
teeth are all fixed to the arm 42 ', which is disposed substantially perpendicular to the plane zy,
and thus rather along the x-axis and perpendicular to the arm 40'.
[0087]
Finally, the comb 241 is associated with a stationary comb 24'1 whose teeth are fixed to the
stationary part 52 'of the device and the movable comb 24 cooperates with the stationary comb
24'. Similarly, the comb 241 cooperates with the comb 42'1. The alternating relative
arrangement of the teeth of these two combs 241, 24'1 is similar or identical to that described
above for the two combs 24, 24 '. The stationary portion 52 'is also formed in the form of an arm
substantially parallel to the arm 42'. The teeth of the comb 24 ', which are arranged as a row of
teeth parallel to one another, are fixed or connected to this stationary part 52' and the respective
teeth are also arranged in the plane of the direction zy. The arms 52 'and the teeth of the
stationary comb 24'1 are also formed in the substrate 100.
04-05-2019
23
[0088]
Each tooth of each comb 241, 24 ′ 1 can have a thickness measured along the x-axis ranging
from 2 μm or 5 μm to 10 μm or 100 μm. Two adjacent teeth of the same comb are separated
by a distance ranging from 0.5 μm or 1 μm to 3 μm or 10 μm.
[0089]
The teeth of the two combs 241, 24'1 are electrically conductive.
[0090]
When the device is idle, and if a preferred non-zero difference in voltage V 'is established
between the two rows of teeth of two combs 241, 24'1, a pair of parallel plate capacitors are
formed, The two combs take an equilibrium position with respect to each other depending on the
value of the voltage V '.
[0091]
The change of the voltage V 'displaces the teeth of the movable comb 241 relative to the teeth of
the stationary comb 24'1, for example in the direction indicated by the arrow in FIG. 2B, and thus
The arm 40 'is displaced, and displacement or deformation of the wall 25 occurs through the
arms 40, 42, 44, 46, 48, 40'.
[0092]
The device may also comprise guide means 56, 58 in the plane xy in which the movable or
deformable wall membrane and also the detection means move.
[0093]
This means here takes the form of at least one arm 56, 58, for example two arms, arranged
substantially in the direction x, respectively, in the plane xz, but the width in the direction y (from
1 μm to Can be in the range of up to 10 .mu.m) sufficiently small to allow each of the arms
sufficient flexibility in movement resulting from the displacement of the wall 25 in that same
direction x.
[0094]
04-05-2019
24
The arm 56 may be disposed between the side 48 of the moveable frame formed around the
cavity 20 and the arm 42 'of the second moveable comb 241, as illustrated in FIG. 2A. .
Because it is mechanically connected to the stationary part of the device, inducing the
displacement of the movable part in the plane of the substrate 100, and its movable after the
activation means has returned to its initial state before being excited It is possible to return the
part to its starting position.
Using a second arm 58, which can be symmetrical with the arm 56 with respect to an axis
parallel to the y axis, and which is also connected to the stationary part 34 of the device, guides
the movable part It is also possible to perform this function.
Arm 58 may have the same geometrical and elastic properties as arm 56.
[0095]
Furthermore, it is also possible by means of applying an appropriate voltage to the movable parts
of the device, so that each of the electrostatic combs plays its role.
[0096]
This means for applying a voltage may use or combine at least one of the arms 56,58.
For example, the arm 56 is itself mechanically and electrically connected to one of the contact
studs 32 that can apply the desired voltage.
Studs 30, 30 'are also provided in other stationary parts of the device, e.g., parts 52, 52'.
[0097]
If the device comprises two systems of combs on each side of the device, as described above, one
04-05-2019
25
of the movable combs can be used to generate pressure pulses in the cavity 20 Other movable
combs can be used to generate a negative pressure or partial vacuum pulse in the same cavity
20.
Under the influence of one and / or the other of the supply voltages V, V ', one and / or the other
of the actuators generate a force in the plane of the substrate. The resulting force pushes or pulls
the membrane 25. The displacement of the membrane generates a pressure (or negative pressure
or partial vacuum) pulse in the upper cavity 20, which is released through the upper vent 21.
[0098]
Comb means, arms 42, 44, 46, 48 forming a frame around the walls of the cavity 20, arms 40,
40 'are formed in the same substrate 100.
[0099]
The above example may include only a single system of combs.
[0100]
Other examples of devices according to the invention are presented below.
[0101]
According to a second example shown in FIG. 3, the wall 25 is replaced by a wall 250 which is
not deformable but which can be translated along the y-axis.
This wall may also comprise a projection 251 forming a piston associated with the stationary
wall 23, 231, 232 to generate the desired pressure change.
More precisely, this projection 251 penetrates the volume 20, which may cause compression of
the atmosphere present therein.
[0102]
Again, there is a contact on or on or in the top of the substrate 102.
04-05-2019
26
[0103]
The actuation means are the same as in the previous example.
Thus, the device operates in the same manner as already described above.
The actuation of the second system of combs also acts on the movable frame via the side 48 and
the sides 44, 46 and thus also on the wall 250 and the piston 251. This embodiment can also
work in conjunction with a single system of combs.
[0104]
A third embodiment is shown in the side and top views of FIGS. 4A and 4B. FIG. 4A is a crosssectional view along a plane, the contour A1A'1 of which is visible in FIG. 4B (top view).
[0105]
The differences with respect to FIGS. 2A-2B are at the contacts 301, 30'1, 321, which are here on
the rear side, i.e. another difference on the substrate 101 or in the substrate 101 is in the
structure of the wall 25. FIG.
[0106]
The structure of the wall 25 is of the type having a rigid central portion forming a "spring" and
having two deformable portions 253, 255 as a frame.
Under the influence of the actuation means, the rigid part moves and the parts 253, 255 deform.
These parts also return the rigid part to the initial position when the actuation means return to
their initial state after excitation. These portions 253, 255 form a spring connection at the end of
the rigid portion. Here there is a so-called "piston" effect or movement of the movable part.
However, it is also possible in this embodiment to use the deformable membrane or wall
04-05-2019
27
configurations presented above in connection with the preceding figures.
[0107]
The advantage of the "piston" structure (as shown in Figs. 3 or 4A-4B) over the "deformable wall"
(as shown in Figs. 2A-2C) is that the "piston" structure discharges The point is that the amount of
air that can be done is more significant to the displacement amplitude of the wall. However, in
the case of FIG. 3, since the portions 253, 255 form the spring of this figure, an impedance loss
occurs at the end of the piston 251 which is not present on the piston 25 of FIG.
[0108]
The actuation means are the same as in the previous example. Guide arms 56, 58 are now
disposed within the moveable frame, thereby moving the assembly formed by the moveable
walls, frame, and comb, as arms 56 and 58 of FIG. 2B. It becomes possible to induce. It is possible
to make them compact by placing them inside the frame. This alternative form is permitted here
by the occupation of the electrical contacts (in particular the contacts 321) on the rear face. This
was not the case in FIGS. 2A-2C.
[0109]
The fourth example (FIG. 5, top view) uses capacitive excitation applied to the two deformable
members 25, 25 '.
[0110]
The structure of the cavity 20 is different from that described above, but it comprises two
movable or deformable walls 25, 25 ', both arranged so as to be movable or deformable along the
y-axis It is from.
[0111]
The respective ends of the movable walls 25, 25 'are fixed to two parallel stationary walls 231,
232, so this is a deformation of the movable walls that results from this.
04-05-2019
28
Each of these moveable walls has a thickness sufficient to have the desired sensitivity to
movement caused by the actuation means in the plane of the device, measured along the y-axis.
[0112]
Thus, the cavity has a stationary wall 23 ′ ′ parallel to the wall 23 ′ and perpendicular to the
walls 231, 232, in which the second movable wall 25 and one of the ones An opening is provided
through which an arm 40 'can be passed which connects at least a second pair of combs 241,
24'1 which are movable and the other is stationary.
Devices without walls 23 ′, 23 ′ ′ are generally formed in the context of the invention, the
cavity being closed by the walls 23, 25 ′ and the stationary walls 231, 232. In this way, the two
arms 40, 40 'move along the same y-axis depending on the voltage applied to each set of combs.
[0113]
When the voltage supply means 26, 26 'apply the same voltage to both systems of comb, the two
walls 25, 25' move away from each other.
[0114]
Such a device could be made and operated with only one of the two sets of combs 24, 24 'or 241,
24' 1 (and only one deformable wall), but the two sets of FIG. The efficiency is inferior to the
combs 24, 24 'and 241, 24' 1 of
In this example, the device also comprises two additional sets of combs, each having a
displacement along the x-axis. Each comprises a stationary comb 24'a, 241a and a movable comb
24'1a, 24a, as in the comb example already described above, one comb tooth being the other
comb Alternate with the teeth of Each stationary comb is connected to the stationary part 52a,
52'a of the device, including means 30a, 30a 'forming the connecting means of the voltage
supply means 26a, 26'a.
[0115]
04-05-2019
29
Such a device could be made and operated with only one of the additional two sets of combs 24a,
24'a or 241a, 24'1a, but the additional two sets of combs 24a, 24 of FIG. It is less efficient than 'a
and 241a, 24'1a.
[0116]
Each of these two sets of additional combs is arranged such that its teeth are arranged in the
plane zx and so that the movement of the movable comb occurs along the x-axis.
[0117]
Thus, two additional sets of combs may be formed by a 90 ° rotation about the z-axis of the two
sets of combs 24, 24 ', 241, 24'1.
[0118]
The device also comprises a connecting lug 32 connected to the stationary part, here near the
stationary wall 23 defining the cavity 20.
[0119]
Specific coupling means 41a, 41b, 41c, 41d are also provided to connect the two sets of
additional combs and the movable wall 25, 25 '.
[0120]
More specifically, for each additional movable comb 24a, 24'1a, two of the arms 41a, 41b for the
movable comb 24a and the arms 41c, 41d for the movable comb 24'1a One arm is prepared.
[0121]
Each of the arms 41a, 41b is on the opposite side of the movable comb 24a, for example the
midpoint D of the arm 42a, and one zone of the arms 40, 40 ', for example-the wall 25, inside the
arms Of the end of the arm 40, which is arranged near or on the arm 42 of the movable comb 24
at or near the midpoint C of the point C, and-of the wall 25 ' Located on or near the arm 42 'of
the movable comb 241, on the opposite side, at or near the midpoint C' of the arm 42 ', or on the
arm 42' Connect the end of the arm 40 '.
[0122]
Each of the arms 41c, 41d is a movable comb 24'1a, for example the midpoint D 'of the arm 42'a,
04-05-2019
30
and again one zone of the arms 40, 40', for example-of the wall 25 The end of the arm 40,
located on the opposite side, near or on the arm 42 of the movable comb 24, near the midpoint C
of the arm 42, or near its midpoint C, And-near or at the arm 42 'of the movable comb 241 at or
near the midpoint C' of the arm 42 ', which is on the opposite side of the wall 25' Connect the
end of the arm 40 ', which is located' on '.
[0123]
In other words, the four transmission arms 41a, 41b, 41c, 41d are inclined with respect to the x
and y axes (e.g. 45 degrees with respect to said axes) and are respectively placed at the edges of
the arms 42a, 42'a At points D and D ', connect points C and C', which are respectively located on
the edges of the arms 42, 42 '.
[0124]
These four transmission arms form a substantially diamond shape.
Advantageously, when idle, the distance between points D and D 'is the same as the distance
between C and C', so that the transmission arm is square.
[0125]
It is possible to apply a voltage via the means 26a, 26'a, thereby applying a movement to the
movable combs 24a, 24'1a in the plane of the device along the x-axis, If the comb tends to move
away from the cavity 20, the combined action of the arms 41a, 41b, 41c, 41d and the arms 40,
40 'causes the walls 25, 25' to move along the y axis towards the center of the cavity 20. There is
a tendency to return (because the lengths of the arms 41d, 41b are constant).
[0126]
Preferably, when a voltage is applied through the means 26a, 26'a, it tends to generate a
pressure pulse in the cavity 20 but when a voltage is applied to the means 26, 26'a negative
pressure or no There is a tendency to apply a full vacuum pulse into the cavity 20.
[0127]
In this embodiment, as in the previous embodiment, a cavity 20, its walls and actuation means
are formed in the intermediate substrate 100, here with one set of four combs.
04-05-2019
31
[0128]
A structure with two deformable membranes 25, 25 'can be implemented in the context of the
alternative embodiment of FIG. 2B, ie implemented with only two sets of combs as shown in that
figure it can.
However, in this case it is only possible to activate the membrane to generate a negative pressure
or an incomplete vacuum pulse.
[0129]
The fifth embodiment, illustrated in the top view of FIG. 6, comprises means for causing thermal
excitation (through bimorph or asymmetric effect) to be applied to the deformable membrane.
This means is, for example, a thermal actuator or a piezoelectric type.
The structure of this means and its operation are described, for example, in the article "Time and
frequency response of two-arm micromachined thermal actuators", R Hickey et al. Micromech.
Microeng.
It is described on pages 13-40.
Information on the operation of the bimorph actuator can be found at http: // www. pi-france. fr
/ PI% 20 Universite / Page 20% 20. Please refer to htm.
In summary, constraints in the plane of one of the layers of a multilayer stack (in the case of two,
referred to as a bimorph), displacement of this stack occurs in the direction perpendicular to the
plane of these layers .
04-05-2019
32
[0130]
Although two sets of means for generating thermal excitation are shown in FIG. 6, there can only
be one, in which case it operates in only one direction (pressure or negative pressure or partial
vacuum).
[0131]
A sixth embodiment is shown in FIGS. 7A (side cross section) and 7B (top view).
[0132]
It comprises means (in particular for cMUTs) for performing flat piston electrostatic actuation on
a plurality of parallel cavities 20, 20 ', 20 ", 20'".
These cavities or the corresponding openings 21 can be closed by a flexible membrane 281,
which can for example prevent dust or moisture from getting into the device in the case of
loudspeaker type operation Become.
For operation of the cMUT, the membrane can provide a vacuum or partial vacuum seal to the
device (the cMUT operates at resonance).
This film 281 can also be disposed on the other side of the substrate 102 as shown by the
dashed line 281 'in FIG. 7A.
The closing system of the cavity 21 can also be implemented in the context of the previous
embodiments.
[0133]
The device also comprises two cavities 280, 280 'which are closed in the substrate 102 and
which are arranged on the top side of the component, each forming a "back chamber volume".
04-05-2019
33
These two aspects, namely the flexible membrane closing one or more cavities or corresponding
openings 21 and the cavities closed and arranged on the top side of the component, which form
the "back chamber volume", are the invention The present invention can be applied to other
embodiments of
[0134]
In this embodiment, one can see the structure of FIG. 3 in which the piston 251 is arranged, but
this time instead of one cavity 20, four cavities 20 ', 20' ', 20' '' in the direction x That is, they are
arranged adjacent to and parallel to each other in a direction perpendicular to the movement of
the movable combs 24, 241.
Two adjacent cavities can have shared side walls. Thus, the cavities 20 and 20 'share the wall 23'
and the cavities 20 'and 20' 'share the wall 23' 'and the cavities 20' 'and 20' '' have the wall 23 ''
'. Share. Each cavity has an opening facing the piston 251, which gradually opens and closes all
of the cavities simultaneously. The single wall 23 defines its opening and the opposite cavity of
the piston 250.
[0135]
A second pair of arms 56 ', 58' is added to the end that guides the movement of the frame.
[0136]
When this type of component is used for cMUT applications, the interdigital comb is not only
used to generate ultrasound (it operates on transmission as described above), but also to detect
reflected ultrasound useful for analysis Will be activated (when receiving).
In the case of cMUTs, the structural resonant frequency is in the range of about a few MHz, for
example 1 MHz to 10 MHz. In cMUT applications, the cavities 20, 280 may be vacuum sealed or
partially vacuum sealed (via membrane 281).
04-05-2019
34
[0137]
FIG. 10 shows yet another embodiment, where again the capacitive type activation means are
formed by a system of combs, whose teeth are now oriented along the x-axis, It is not oriented
along the y-axis as shown in FIGS. 2A-2B. An arm 40 substantially perpendicular to the wall 25
carries the teeth of the movable part of the comb 27 and the two stationary parts 27 ', 27' 'of the
comb, with respect to the respective rows of teeth, Arranged as already described above for 2B.
[0138]
According to an alternative form of this embodiment, the stationary parts are intended to receive
different voltages V1 and V2, stationary parts 27 ′, 27 ′ ′ and 27′1, Lined up with 27''1.
Guide arms 56, 58 may, for example, be provided between the means by which voltage V1 can be
applied and the means by which voltage V2 can be applied. Since two different voltages can be
applied, one of the voltages is used to activate the membrane, for example in the right direction,
in the compression of the cavity 20, and the other voltage is used to It is possible to operate the
membrane in other directions, for example in the left direction, under negative pressure or
partial vacuum.
[0139]
Preferably, as illustrated in FIG. 11, an asymmetric air gap is formed, at idle, between each
movable electrode and the stationary electrode that is its frame. For example, the air gap
between the movable electrode 240 'and the first adjacent stationary electrode 2401
(respectively, the first adjacent stationary electrode 2402) may be between the two adjacent
electrodes Is about 1/3 (2/3 each) of the distance
[0140]
8A-8G illustrate a method of manufacturing a device according to the present invention. In this
example, there are contacts on the front and a cavity 28 on the rear.
[0141]
04-05-2019
35
The method involves attaching a second substrate.
[0142]
Starting with the SOI substrate (in FIG. 8A) (eg using a 0.5 μm thick buried oxide (BOX) 103).
Alternatively, one starts from a standard substrate 101 where a deposition 103 of a sacrificial
layer (oxide) and a deposition 100 of a semiconductor material, eg silicon or polycrystalline SiGe,
are performed.
[0143]
Then metal deposition (eg Ti / Au, or AISI ... Is performed, and further, lithography and etching of
the contacts 30, 30 'are performed. It is also possible to form the contacts on the rear side using
the same technique.
[0144]
Then perform lithography and etching of the silicon surface (FIG. 8B), in particular the acoustic
cavity 20 and the mechanical activity, including the movable or deformable wall 25 and the
actuating element (capacitive comb or thermal excitation means) The particular structure is
defined, the details of which are not shown here, and the etching mask used is adapted to
constitute suitable measures depending on the type of operation to be performed.
[0145]
In addition, silicon oxide (SiO 2) vapor deposition 104 is performed to a thickness of about 0.8
μm on the base of the conventional Si substrate 102 (FIG. 8C).
[0146]
Then, lithography and etching (partial or complete) of oxide 104 and silicon 102 are performed
to form openings 106, 106 ', 106' 'for pressure inlets and contact openings.
[0147]
04-05-2019
36
The two substrates are then aligned (FIG. 8D) and sealed (such as by direct seal, eutectic, or
polymer, or anode).
[0148]
Then, lithography and etching (FIG. 8E) of the openings of the cavities 28, 28 'are performed on
the rear surface ("back chamber volume").
[0149]
The opening of the cavity 21 and the contacts 30, 30 'are formed by thinning the front ("back
grinding") (Fig. 8F).
[0150]
Finally, the movable structure (FIG. 8G) is released by removing portions of the oxide sacrificial
layer 103, 104 with HF etching (eg, steam).
[0151]
Following the same progression, the method begins with a standard substrate 300 (FIG. 9A)
made of a semiconductor material such as, for example, silicon.
[0152]
Deposition of the sacrificial layer 301 is performed on the substrate (FIG. 9B), for example, the
thickness of the oxide layer, again in the example, may be equal to about 0.5 μm.
[0153]
Then, an active layer 302 (FIG. 9C) of poly-Si or poly-SiGe is deposited on the sacrificial layer
301, and its thickness may be, for example, about 10 μm.
Then, return to the previous method from FIG. 8A.
[0154]
04-05-2019
37
In general, the sacrificial layers 103, 104 are, for example, in the range of several tens of nm to
several microns, for example 100 nm or 500 nm to 1 μm or 2 μm.
The active layers 100, 101, 102 (made, for example, of Si or SiGe, respectively) are, for example,
in the range from a few μm to a few tens of μm, even a few hundred μm, for example 5 μm to
10 μm is there.
[0155]
In the case of a closed cavity made on the substrate 102 (structure of FIG. 7A), it is possible to
take advantage of the step of etching the opening 21, and the cavities 280, 280 ′ etch
simultaneously with this opening 21. be able to.
[0156]
In the case of an open cavity within the substrate 101 (e.g., the structure of FIG. 4), the openings
28 need to be etched across the entire thickness of the substrate 101.
For this reason, although the manufacturing method is complicated, “back chamber volume” is
more effective in this case than in the case of FIG. 7A.
[0157]
The present invention is applied to the manufacture of pressure pulse generators for digital
loudspeakers, in particular for general consumer applications (mobile phones, game consoles,
MP3 players, televisions etc.).
[0158]
It also applies to ultrasonic pulse generators for cMUTs, in particular medical or industrial
applications (ultrasound probes, ultrasound examinations, nondestructive examinations etc).
[0159]
It can also be used as a pneumatic actuator (e.g. as a pump etc).
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[0160]
Reference Signs List 1 substrate 3 means for forming electrical contacts 4 coil 5 permanent
magnet 6 outlet 20, 20 ', 20' ', 20' '' parallel cavity 21 opening, upper vent 23, 231, 232 side wall
23 ', 23' ' , 23 '' 'wall 24 means 24' comb 241 movable comb 24'1 stationary comb 24'a, 241a
stationary comb 24'1a, 24a movable comb 25 wall or membrane 25 ', 25 '', 25 '' 'wall 250 upper
part 25'0 lower part 26, 26' means, voltage supply means 26a, 26'a voltage supply means 27
comb 27 ', 27' 'stationary part 27' 1, 27 '' 1 stationary part 28, 28 'lower secondary cavity 30,
30', 32 contact zone 30a, 30a 'means 32 contact studs 40, 4 'Arms 41a, 41b, 41c, 41d coupling
means 42, 42', 42'a arms 43, 43 'stoppers 44, 46, 48 arms or sides 52, 52' stationary parts 52a,
52'a stationary parts 56, 56 'arm 58, 58' arm 100, 101, 102 substrate 101 'upper surface 102'
lower surface 103 embedded oxide (BOX) 104 deposition 106, 106 ', 106' 'opening 240'
movable electrode 2401, 2402 first adjacent stationary electrode 251 piston 253, 255 side part
280, 280 'cavity 281, 281' membrane 301 sacrificial layer 302 active layer
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39
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