WO2011021341A1

WO2011021341A1 - Electromechanical converter, microphone, and method for manufacturing electromechanical converter

Info

Publication number: WO2011021341A1
Application number: PCT/JP2010/004200
Authority: WO
Inventors: 冨田佳宏
Original assignee: パナソニック株式会社
Priority date: 2009-08-20
Filing date: 2010-06-24
Publication date: 2011-02-24
Also published as: JP2011044890A

Abstract

A microphone (100) is provided with: a vibrating membrane (2), which has a first surface and a second surface that is on the reverse side of the first surface, and which has a first vibrating region (6) and a second vibrating region (7) that is disposed at the periphery of the first vibrating region (6); a fixed membrane (3) disposed to face the first surface of the vibrating membrane (2); and a netlike frame body (8), which is disposed, as a reinforcing section, in the first vibrating region (6) on the second surface of the vibrating membrane. Vibration of the vibrating membrane (2) is converted into electric signals by means of a capacitor composed of the vibrating membrane (2) and the fixed membrane (3).

Description

Electromechanical transducer, microphone, and method of manufacturing electromechanical transducer

The present invention relates to an electromechanical transducer, in particular, a small microphone and a manufacturing method thereof.

With the diversification of functions of personal electronic devices such as mobile phones and mobile terminals, electromechanical converters that detect or output various information such as heat, sound, pressure, acceleration, etc., are now installed inside. Therefore, there is a demand for miniaturization, high performance, and high stability. A small microphone is also one of electromechanical converters that convert sound pressure into an electric signal, and both miniaturization, high sensitivity, high S / N ratio, and high stability are required.

In recent years, electromechanical transducers that have been reduced in size and weight by using MEMS (Micro Electro Mechanical Systems, micro electromechanical element) technology for small microphones and the like have appeared, and refer to FIGS. 8A to 8C for their configurations. However, it will be described below.

FIG. 8A is a top view of a conventional MEMS microphone, and FIGS. 8B and 8C are cross-sectional views taken along the line BB shown in FIG. 8A. The vibrating membrane 102 is formed by a frame body 101 provided with an opening penetrating a silicon substrate. Is supported and fixed on the outer periphery thereof. The fixed film 103 is arranged with a predetermined distance from the vibration film 102 by a spacer 104, and the fixed film 103 is provided with a sound hole 105 for transmitting sound pressure to the vibration film 102.

The vibration film 102 and the fixed film 103 are conductive and constitute a capacitor separated by a predetermined interval, and an electric field is applied between the vibration film 102 and the fixed film 103. In this electric field, as shown in FIG. 8C, when the vibration film 102 vibrates due to the sound pressure transmitted from the sound hole 105, an electric charge is induced between the vibration film 102 and the fixed film 103, and electromechanical conversion is performed. The sound pressure transmitted from the sound hole 105 is output as an electrical signal.

In recent years, the use of MEMS technology capable of fine processing has been attempted to reduce the size and weight of the microphone so that it can be used in applications where downsizing of mobile phones and the like is strongly demanded.

For example, there are the following

Patent Documents

1 and 2 as prior art documents relating to such a microphone. Patent Document 2 below is an example in which the vibrating membrane 102 has a cantilever structure.

JP 2005-086535 Gazette JP-T-2001-518246

In the above conventional example, there is a conflicting relationship between miniaturization and high performance of the microphone, and there is a problem that it is difficult to achieve both.

Specifically, a vibration membrane of a conventional electromechanical transducer includes a first vibration region that vibrates due to sound pressure, and a second vibration region that is disposed on the outer periphery of the first vibration region. If the frame is made smaller and the vibration membrane is made smaller in order to reduce the size of the electromechanical transducer, the distance of the second vibration region from the first vibration region to the frame is supported and fixed to the frame by the second vibration region. Therefore, the displacement of the vibration in the first vibration region when receiving the sound pressure is reduced, the induced charge is also reduced, and the sensitivity is lowered.

In order to minimize such sensitivity reduction and reduce the size, the tension applied to the diaphragm by the frame is reduced, the diaphragm is thinned to reduce the bending rigidity and reduce the weight, and between the diaphragm and the fixed membrane. The method of raising the electric field to be applied is taken.

However, if the tension of the vibrating membrane is reduced or the vibrating membrane is made thinner, the entire vibrating membrane is easily displaced, and the first vibrating region is likely to bend, and the first vibrating region is bent by the attractive force due to the applied electric field. There is a problem that the sensitivity is lowered due to the local portion approaching or contacting the fixing film locally. In addition, increasing the electric field to be applied also increases the bending of the first vibration region, which causes a decrease in sensitivity.

The present invention aims to achieve both miniaturization and high performance of an electromechanical transducer, which has been a problem with conventional electromechanical transducers.

In order to solve this problem, an electromechanical transducer according to an embodiment of the present invention has a first surface and a second surface opposite to the first surface, and includes a first vibration region and the first surface. A vibration film having a second vibration region disposed around one vibration region, a fixed film disposed to face the first surface of the vibration film, and the second surface of the vibration film. And a reinforcing part disposed in the first vibration region, and the vibration of the vibration film is converted into an electric signal by a capacitor constituted by the vibration film and the fixed film.

According to this configuration, since the bending rigidity of the first vibration region can be increased by forming the reinforcing portion in the first vibration region, it is possible to suppress the bending of the first vibration region due to an applied voltage or an external force. Therefore, even if the film thickness of the vibrating membrane is reduced or the tension is lowered in order to increase the vibration displacement of the first vibration region, the bending of the first vibration region is suppressed, and the second vibration region is suppressed by sound pressure or the like. It can be easily bent. Therefore, the first vibration region suppresses the deflection and suppresses the proximity and contact with the fixed film, and the second vibration region can be easily bent to increase the displacement of the entire first vibration region due to the sound pressure or the like, The vibration membrane can be prevented from locally contacting or approaching the fixed membrane, so that both the miniaturization and high performance of the electromechanical transducer can be achieved.

Here, the reinforcing portion may be formed in a mesh shape having a plurality of openings, and the first vibration region may have a third vibration region for each of the openings.

According to this configuration, since the reinforcing portion is formed in a mesh shape having openings, and each of the plurality of openings has the third vibration region, not only the entire first vibration region but also each third vibration region. Vibration can also be obtained, and the sensitivity of the electromechanical transducer can be improved. Further, by reducing the thickness of the vibration film constituting the third vibration region or decreasing the tension, the displacement of each third vibration region can be increased, and the sensitivity can be further improved.

Here, the reinforcing portion may be formed integrally with the vibrating membrane.

According to this configuration, the bending rigidity of the first vibration region can be further increased, and the bending of the first vibration region can be further suppressed.

Here, the reinforcing portion may be formed as a mesh-shaped recess from the first surface of the vibrating membrane.

According to this configuration, the reinforcing portion can be reduced in weight and the bending rigidity of the first vibration region can be increased, so that the bending of the first vibration region can be further suppressed.

Here, the second vibration area may be bent and arranged at a position farther from the fixed film than the first vibration area.

According to this configuration, the signal charge distributed between the second vibration region and the fixed film can be reduced, and the vibration in the first vibration region can be efficiently converted into an electric signal.

Here, each of the openings may have a hexagonal shape.

Here, each of the openings may have a circular shape.

Here, the openings may be arranged such that the adjacent openings are in a staggered arrangement.

Here, the opening may be arranged such that the adjacent opening has a honeycomb shape.

Here, the opening may be formed so as to increase in shape as it is arranged from the center of the first vibration region toward the outer periphery.

According to this configuration, it is possible to widen the frequency response characteristics of the electromechanical transducer by changing the shape and arrangement of the openings, and it is possible to efficiently increase the rigidity of the first vibration region. Therefore, the performance of the electromechanical converter can be further increased.

Here, an electric charge may be injected into at least one of the vibration film and the fixed film, and an electret capacitor may be configured by the vibration film and the fixed film.

According to this configuration, the circuit configuration for applying an electric field between the vibrating membrane and the fixed membrane can be omitted, so that the electromechanical transducer can be further downsized.

In addition, the present invention can be realized not only as an electromechanical converter but also as a microphone having the above-described configuration that converts vibration of the vibrating membrane due to sound pressure into an electric signal.

In order to solve this problem, a method of manufacturing an electromechanical converter according to an embodiment of the present invention includes a step of forming a mesh-like groove on a surface of a substrate, and the vibration film on the surface of the substrate and the groove. And a step of integrally forming a reinforcing portion that suppresses the bending of the first vibration region of the vibration film.

According to this configuration, the mesh-shaped reinforcing portion can be easily formed integrally with the vibration membrane in the first vibration region, and an electromechanical transducer having high bending rigidity in the first vibration region can be easily formed. it can.

Here, the thickness of the vibration film and the reinforcing portion formed on the surface of the substrate, the side surface and the bottom surface of the groove portion may be uniform.

According to this configuration, it is possible to easily form an electromechanical transducer in which the vibration film is formed to have a uniform thickness and the reinforcing portion is lightened and the bending rigidity of the first vibration region is high.

According to the present invention, it is possible to suppress the bending of the first vibration region and achieve both the miniaturization and the high performance of the electromechanical transducer.

FIG. 1 is a perspective sectional view of an electromechanical transducer according to a first embodiment of the present invention. FIG. 2 is a top view of the electromechanical transducer according to the first embodiment of the present invention. FIG. 3A is a cross-sectional view of an electromechanical transducer comparing the present invention with a conventional example. FIG. 3B is a cross-sectional view of an electromechanical transducer comparing the present invention with a conventional example. FIG. 4A is a cross-sectional view showing the manufacturing process of the electromechanical transducer according to the first embodiment of the present invention. FIG. 4B is a cross-sectional view showing the manufacturing process of the electromechanical transducer according to the first embodiment of the present invention. FIG. 4C is a cross-sectional view showing the manufacturing process of the electromechanical transducer according to the first embodiment of the present invention. FIG. 4D is a cross-sectional view illustrating the manufacturing process of the electromechanical transducer according to the first embodiment of the invention. FIG. 5A is a cross-sectional view illustrating the manufacturing process of the electromechanical transducer according to the second embodiment of the present invention. FIG. 5B is a cross-sectional view illustrating the manufacturing process of the electromechanical transducer according to the second embodiment of the present invention. FIG. 6 is a top view of an electromechanical transducer according to a modification of the present invention. FIG. 7 is a top view of an electromechanical transducer according to another modification of the present invention. FIG. 8A is a top view of an electromechanical transducer according to the prior art. FIG. 8B is a cross-sectional view of an electromechanical transducer according to the prior art. FIG. 8C is a cross-sectional view of an electromechanical transducer according to the prior art.

Hereinafter, the configuration of the electromechanical converter according to the present invention will be described with reference to an example of a microphone. The present invention can be applied to heat and pressure sensor devices in general and electrostatic actuators as electromechanical transducers having movable (vibrating) membranes having the same configuration, but this is for illustrative purposes only. It is not intended to be limited to

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings. In the present embodiment, a microphone including a reinforcing portion arranged in the first vibration region on the second surface of the vibration membrane will be described. According to this configuration, since the bending rigidity of the first vibration region can be increased by forming the reinforcing portion in the first vibration region, it is possible to suppress bending of the first vibration region due to an applied voltage or an external force.

FIG. 1 is a perspective sectional view of the microphone 100 of the present embodiment, and FIG. 2 is a top view thereof. In addition, in order to make the configuration of the vibrating membrane 2 easier to understand, the display of the fixed membrane 3 is omitted inside the frame body 1 in the top view of the microphone 100 of FIG.

As shown in FIG. 1, the microphone 100 includes a frame body 1, a vibration film 2, a spacer 4, a fixed film 3, a mesh frame body 8 as a reinforcing portion, and an extraction electrode 10.

The vibration film 2 is made of polysilicon, and has a first vibration region 6 that vibrates due to sound pressure, and a second vibration region 7 disposed around the first vibration region 6. Further, the first vibration region 6 includes a mesh frame 8 as a reinforcing portion for preventing the first vibration region 6 from bending over the entire back surface. The mesh frame 8 is made of polysilicon formed in a mesh shape having a plurality of openings 9, and the first vibration regions 6 arranged at the positions of the openings 9 respectively form the minute diaphragms 2a. Yes. The minute diaphragm 2a corresponds to the third vibration region in the present invention, and the front and back surfaces of the vibration film 2 correspond to the first surface and the second surface in the present invention, respectively.

In addition, as shown in FIG. 2, the openings 9 of the mesh frame 8 have hexagonal shapes when viewed from the upper surface, and are arranged in a staggered manner between the adjacent openings 9. By arranging them in such a way, it is devised so that the bending rigidity of the mesh frame 8 does not become weak in a specific direction. FIG. 2 shows an example of a honeycomb structure having a particularly strong strength, that is, a regular hexagonal micro-diaphragm 2a arranged in a honeycomb shape without a gap. Note that such a honeycomb structure is not limited to a regular hexagon, and other polygonal micro diaphragms may be arranged without gaps.

As shown in FIG. 1, the vibration membrane 2 is supported in the second vibration region by a frame body 1 that forms the outer shape of the microphone 100. The frame 1 is made of a silicon substrate having a rhombus outer peripheral shape, and the inner peripheral shape of the frame 1 is formed in a hexagonal shape through the front and back surfaces of the silicon substrate.

Further, as shown in FIG. 1, the fixed film 3 is disposed on the surface of the vibration film 2 so as to be opposed to each other with a predetermined distance by a spacer 4.

The fixed film 3 includes a plurality of sound holes 5, and the sound pressure from the outside is transmitted to the vibration film 2 through the sound holes 5, and the vibration film 2 vibrates according to the sound pressure. The vibration film 2 and the fixed film 3 have conductivity, and a predetermined electric field is applied between the vibration film 2 and the fixed film 3, and the vibration film 2 vibrates due to sound pressure. As a result, an electric charge according to the displacement of the vibration film 2 is induced between the vibration film 2 and the fixed film 3 constituting the capacitor with a predetermined interval.

As a method of applying an electric field between the vibrating membrane 2 and the fixed membrane 3, a method of applying a voltage by an external power source, or by electrifying the vibrating membrane 2 or the fixed membrane 3 by injecting an electric charge in advance to fix the electret capacitor There is a way to configure. In the electret capacitor method, an electric field can be generated between the vibrating membrane 2 and the fixed membrane 3 without applying an external voltage.

Further, as shown in FIG. 1, an extraction electrode 10 for taking out an electric signal is formed at a position corresponding to a diamond-shaped acute margin of the frame 1 on the surface of the fixed film 3. The extraction electrodes 10 on both sides are electrically connected to the vibration film 2 and the fixed film 3, respectively. With such a configuration, a change in electric field generated between the vibrating membrane 2 and the fixed membrane 3 due to vibration displacement of the vibrating membrane 2 is read, and a mechanical change called sound pressure received by the vibrating membrane 2 is converted into an electrical signal. ing.

Next, the difference between the configuration of the microphone according to the present embodiment and the microphone according to the conventional example will be described with reference to FIGS. 3A, 3B, and 8C.

FIG. 3A is a cross-sectional view taken along the line AA in FIG. 2 and is a cross-sectional view showing the microphone according to the present embodiment. FIG. 8C is a cross-sectional view showing a microphone according to a conventional example. FIG. 3B is an enlarged cross-sectional view in the vicinity of a portion P in FIG. 3A.

In the configuration of the microphone according to the conventional example shown in FIG. 8C, the vibration film 102 is formed of a thin film having a uniform thickness. Therefore, the vibration film 102 is attracted to the fixed film 103 by the electric field applied between the vibration film 102 and the fixed film 103 according to the sound pressure from the sound hole 105, and the center of the vibration film 102 becomes closer to the fixed film 103. It will bend to approach. When the vibration film 102 is extremely bent, the vibration film 102 is locally in contact with the fixed film 103 and vibration is suppressed, and sensitivity as a microphone is not obtained.

On the other hand, as shown in FIG. 3A, in the configuration of the microphone according to the present embodiment, since the back surface of the first vibration region 6 is supported by the mesh frame 8, Deflection is suppressed. The first vibration region 6 is supported and fixed to the frame body 1 via the second vibration region 7, and when the sound pressure is applied by making the vibration film 2 thin and making it easy to bend. The displacement of the first vibration region 6 is easily generated. Here, even if the film thickness of the vibrating membrane 2 is reduced, the first vibrating region 6 is reinforced by the mesh frame body 8 and thus does not generate a large deflection as in the conventional microphone. Therefore, local contact between the vibrating membrane 2 and the fixed membrane 3 can be suppressed. Therefore, if the vibrating membrane 2 is made thin and easily bent, the second vibrating region 7 is greatly displaced, and the first vibrating region 6 is largely displaced in a state substantially parallel to the fixed membrane 3 and is locally localized. It becomes possible to suppress an unnecessary contact.

Further, as shown in FIG. 8C, in the configuration of the microphone according to the conventional example, the center of the vibration film 102 is closer to the fixed film 103, and thus the sensitivity of the vibration of the center vibration film 102 is higher. Therefore, the center of the vibration film 102 effectively contributes to the sensitivity of the condenser microphone, and the outer peripheral portion of the vibration film 102 contributes less to the sensitivity of the condenser microphone. On the other hand, as shown in FIG. 3A, in the configuration of the microphone according to the present embodiment, the entire first vibration region 6 vibrates with respect to the sound pressure from the sound hole 5 in a translational manner. The vibration of the entire 6 can be effectively extracted as a signal of the condenser microphone.

Further, when the mesh frame 8 has an opening 9, as shown in FIG. 3B, which is an enlarged cross-sectional view in the vicinity of the portion P in FIG. 3A, the micro-diaphragm 2a disposed in the opening 9 of the mesh frame 8 By thinning, the micro diaphragm 2a arranged in each opening 9 can be easily vibrated by sound pressure. Therefore, in addition to the displacement due to the sound pressure of the entire first vibration region 6, each micro diaphragm 2a is also displaced by the sound pressure as shown in FIG. 3B, so that the sensitivity as a microphone can be further increased. Since the individual openings 9 of the microphone according to the present embodiment are much smaller than the openings of the microphone frame 1 according to the conventional example, even if the microdiaphragm 2a is bent, it contacts the fixed film 3. It can be controlled not to bend as much.

The microphone manufacturing method according to the present embodiment will be described with reference to FIGS. 4A to 4D.

First, as shown in FIG. 4A, a silicon substrate is prepared as the support substrate 11 constituting the frame body 1, and the groove portion 15 corresponding to the shape of the mesh frame body 8 is formed on the surface of the support substrate 11. A barrier film 12 is formed so as to cover the entire surface of the support substrate 11 including the bottom and side surfaces. For example, the barrier film 12 is formed of a silicon nitride film.

Next, as shown in FIG. 4B, a polysilicon film is formed as the vibration film 2. The polysilicon film is formed, for example, by CVD (Chemical Vapor Deposition) so as to cover the barrier film 12 and fill the groove 15 so that the mesh frame 8 and the vibration film 2 are integrated. To form.

Next, as shown in FIG. 4C, an insulating film is formed using BPSG (Boro-Phospho Silicate Glass), for example, as the spacer 4 so as to cover the vibration film 2. Further, a polysilicon film is formed thereon as the fixed film 3. Then, a plurality of sound holes 5 penetrating the polysilicon film are formed by etching and removing a part of the polysilicon film to be the fixed film 3 into a hole shape.

Furthermore, as shown in FIG. 4D, the insulating film to be the spacer 4 is removed through the sound hole 5 by sacrificial layer etching, leaving a part of the outer periphery, thereby forming the frame-shaped spacer 4. Accordingly, the vibration film 2 and the fixed film 3 are arranged to face each other at a predetermined interval.

Thereafter, the frame 1 is provided by etching the support substrate 11 from the back surface to the barrier film 12 while leaving a part of the outer periphery. Further, the barrier film 12 is also removed by etching, and the mesh frame 8 is completed on the back surface of the first vibration region 6.

In the microphone manufacturing method according to the present embodiment, the vibrating membrane 2 and the mesh frame 8 are formed of the same material, but effects unique to the present invention can be obtained even when the members are separate members.

In addition, since the support substrate 11 is silicon and the vibration film 2 is polysilicon, the barrier film 12 is provided to secure a selection ratio when the support substrate 11 is etched from the back surface in consideration of the difference in etching rate. If the support substrate 11 and the vibration film 2 are a combination of materials capable of providing an etching selectivity, the barrier film 12 need not be provided.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. 5A and 5B. The second embodiment is different from the first embodiment in that in the microphone manufacturing method, the entire groove formed in the support substrate is not filled with polysilicon, and the surface of the support substrate, the side surface of the groove, The polysilicon film is formed so that the thickness of the polysilicon film is uniform on the bottom surface. That is, the reinforcing portion is formed as a mesh-shaped concave portion from the surface of the vibration film.

FIG. 5A is a cross-sectional view showing a part of the process of manufacturing the microphone according to the second embodiment of the present invention, and FIG. 5B is a cross-sectional view showing the structure of the completed microphone.

As in the first embodiment, a silicon substrate is prepared as the support substrate 11 constituting the frame 1. Then, a groove 25 corresponding to the shape of the mesh frame 28 and the second vibration region 27 is formed on the surface of the support substrate 11. Further, the barrier film 12 is formed so as to cover the entire surface of the support substrate 11 including the bottom surface and side surfaces of the groove 25.

In the first embodiment, the polysilicon film of the mesh frame 8 is formed so as to fill the groove 15 by the CVD method, whereas in this embodiment, the polysilicon film is shown in FIG. 5A. As described above, the polysilicon film of the vibration film 22 is formed so as not to completely fill the groove 25. Specifically, a silicon nitride film is formed as the barrier film 12 so as to cover the surface of the support substrate 11 in which the groove 25 is formed. Furthermore, by forming a polysilicon film of the vibration film 22 by CVD so as to cover it, the thickness of the polysilicon formed on the side surface and the bottom surface of the groove 25 is made uniform, The mesh frame 28 and the vibration film 22 are integrally formed.

Thereafter, as in the first embodiment, an insulating film is formed as the spacer 4 by using, for example, BPSG as a constituent material so as to cover the vibration film 22. Further, a polysilicon film is formed thereon as the fixed film 3. Then, a plurality of sound holes 5 penetrating the polysilicon film are formed by etching and removing a part of the polysilicon film to be the fixed film 3 into a hole shape.

Further, the insulating film serving as the spacer 4 is removed by sacrificial layer etching through the sound hole 5 while leaving a part of the outer periphery, thereby forming the frame-shaped spacer 4. Thus, the vibration film 22 and the fixed film 3 are arranged to face each other at a predetermined interval.

Thereafter, the frame 1 is provided by etching the support substrate 11 from the back surface to the barrier film 12 while leaving a part of the outer periphery, and the barrier film 12 is also etched away, and an opening 29 is formed on the back surface of the first vibration region 26. A mesh-like frame body 28 having the above is completed.

In the completed microphone, as shown in FIG. 5B, the vibration film 22 and the mesh frame 28 have a mesh-shaped recess 30 from the surface of the vibration film 22, and the mesh-shaped recess 30 causes the first vibration region 26 to be formed. The structure is separated into a plurality of minute diaphragms 22a.

By doing so, the bending rigidity of the vibration film 22 is increased, and the bending of the first vibration region 26 can be suppressed. Furthermore, since the mesh frame 28 can be formed of a thin film having the same film thickness as the vibration film 22, it is possible to suppress a decrease in sensitivity of the microphone due to an increase in the weight of the first vibration region 26 due to the mesh frame 28.

Further, by forming a mesh-like groove portion 25 corresponding to the shape of the second vibration region 27, as shown in FIG. 5B, the distance between the vibration film 22 and the fixed film 3 in the second vibration region 27 is changed to the first. It can be separated from the vibration region 26. The second vibration region 27, which has a small displacement even when subjected to sound pressure, has a small contribution to charge generation. This is also distributed to the capacity of the second vibration region 27 and the sensitivity is lowered. Accordingly, by separating the vibration film 22 and the fixed film 3 in the second vibration region 27, the signal charge distributed to the second vibration region 27 can be reduced, and a decrease in sensitivity can be suppressed.

Similarly, in the present embodiment, the vibration film 22 in the part constituting the mesh frame 28 is moved away from the fixed film 3 rather than the vibration film 22 in the part constituting the micro diaphragm 22 a in the first vibration region 26. The signal charge distributed between the mesh frame 28 and the fixed film 3 is also reduced, so that the signal charge in the micro diaphragm 22a that vibrates due to the sound pressure from the sound hole 5 can be effectively used. It can be taken out.

(Modification 1)
Hereinafter, a modification of the first embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 6, the microphone that is the electromechanical transducer according to the present modification has a mesh shape formed on the back surface of the first vibration region 36 with respect to the configuration of FIG. 2 illustrating the first embodiment. The difference is that the sizes of the plurality of openings 39 of the frame 38 are designed to be different. By doing in this way, the response characteristic with respect to the sound pressure for each micro diaphragm 32a can be changed. Frequency response characteristics are important for a microphone, but it is possible to control and design the frequency response of the entire microphone at a wide frequency by configuring the microphone with a micro diaphragm 32a formed in a plurality of sizes and having a plurality of response characteristics. Is possible.

In particular, as shown in FIG. 6, when the micro diaphragm 32 a disposed near the center of the first vibration region 36 is smaller and the outer periphery is larger in size, the entire first vibration region 36 and the fixed film 3 The displacement of the vibration due to the sound pressure can be obtained efficiently while ensuring a substantially uniform distance. That is, although the first vibration region 36 of the vibration film 32 is reinforced by the mesh frame 38, a slight deflection occurs, and the center is closer to the fixed film 3. Therefore, the size of the micro diaphragm 32a in the vicinity of the center of the first vibration region 36 is reduced to suppress the vibration displacement of each micro diaphragm 32a in the vicinity of the center, and the size of the micro diaphragm 32a is made closer to the vicinity of the second vibration region 37. The displacement is increased so that the displacement of the minute diaphragm 32a is increased. Therefore, it is possible to obtain a vibration displacement by sound pressure efficiently while ensuring a substantially uniform distance from the fixed film 3 in the entire first vibration region 36.

(Modification 2)
Hereinafter, another modification of the first embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 7, the microphone that is the electromechanical transducer according to the present modification has a mesh shape formed on the back surface of the first vibration region 46 with respect to the configuration of FIG. 2 illustrating the first embodiment. The plurality of openings 49 of the frame body 48 are different in that each shape is circular. As described above, the shapes of the opening 49 and the minute diaphragm 42a are not limited to hexagons, and the same effect can be obtained even in a circular shape. In particular, in order to efficiently vibrate the minute diaphragm 42a by sound pressure, a shape closer to a perfect circle is preferable to a flat shape having a different vertical and horizontal size. Similarly, the shape of the outer periphery of the second vibration region 47, that is, the shape of the outer periphery of the vibration film 42 is not limited to a hexagon, and may be changed to other shapes.

The present invention is not limited to the embodiment described above, various improvements without departing from the gist of the present invention may be carried out deformation.

For example, in the embodiment of the present invention described above, single-layer thin films are described as the vibration film and the fixed film, but the effects of the present invention are not limited to this configuration. For example, the same effect can be obtained even if the vibration film is a multilayer film. Specifically, an insulating film may be formed on both sides of polysilicon as the vibration film, or a charge holding layer for holding injected charge in the case of the electret method may be formed. Further, the structure of the reinforcing portion is not limited to the mesh frame having an opening, but may be a plate shape having no opening.

Whether the mesh frame has a robust frame structure as in the first embodiment or a bent vibration film as in the second embodiment determines whether the vibration film is bent or not. Can be selected depending on whether the emphasis is on the suppression of weight increase. Further, in the above-described embodiment, the mesh frame body has a honeycomb structure in which fine diaphragms having regular hexagonal openings are arranged in a honeycomb shape without gaps. However, such a honeycomb structure is not limited to a regular hexagonal shape. Alternatively, circular or other polygonal micro diaphragms may be arranged without gaps.

Further, the constituent materials such as the vibration film, the fixed film, and the spacer are not limited to the above-described constituent materials, and any constituent material other than polysilicon and BPSG may be used. The film forming method is not limited to the CVD method, and any method may be used. The etching method may be any method such as dry etching or wet etching.

Further, in the above-described embodiment, the microphone that converts the vibration of the diaphragm corresponding to the sound pressure into an electric signal has been described as an example. It may be used in an electromechanical transducer for sensing or outputting information.

As described above, the present invention suppresses the proximity and contact with the fixed film by suppressing the bending of the first vibration region of the vibration film by the mesh frame. In addition, by making the second vibration region supporting the first vibration region easy to bend, the displacement of the entire first vibration region due to sound pressure or the like is increased. Therefore, it is possible to achieve both miniaturization and high performance of the electromechanical transducer that senses or outputs various information such as heat, sound, pressure, and acceleration.

Therefore, it can contribute to diversification of functions, high performance, small size and light weight of personal electronic devices such as mobile phones and mobile terminals.

1, 101

Frame

2, 22, 32, 42, 102

Vibration membranes

2a, 22a, 32a, 42a Micro diaphragm (third vibration region)
3, 103

Fixed membrane

6, 26, 36, 46

First vibration region

7, 27, 37, 47

Second vibration region

8, 28, 38, 48 Mesh frame (reinforcement part)
9, 29, 39, 49 Opening 11 Support substrate (substrate)
15, 25 Groove 30 Reticulated recess 100 Microphone (electromechanical transducer)

Claims

A vibration film having a first surface and a second surface opposite to the first surface, the first vibration region and a second vibration region disposed around the first vibration region; ,
A fixed film disposed opposite to the first surface of the vibration film;
A reinforcing portion disposed in the first vibration region on the second surface of the vibration membrane,
An electromechanical converter that converts vibration of the vibration film into an electric signal by a capacitor configured by the vibration film and the fixed film.
The reinforcing portion is formed in a mesh shape having a plurality of openings,
The electromechanical transducer according to claim 1, wherein the first vibration area has a third vibration area for each of the openings.
The electromechanical converter according to claim 1, wherein the reinforcing portion is formed integrally with the vibrating membrane.
The electromechanical transducer according to claim 3, wherein the reinforcing portion is formed as a mesh-shaped recess from the first surface of the vibrating membrane.
5. The electromechanical transducer according to claim 4, wherein the second vibration region is bent and disposed at a position farther from the fixed film than the first vibration region.
The electromechanical transducer according to claim 2, wherein each of the openings has a hexagonal shape.
The electromechanical transducer according to claim 2, wherein each of the openings has a circular shape.
The electromechanical transducer according to claim 2, wherein the openings are arranged such that adjacent openings are arranged in a staggered arrangement.
The electromechanical transducer according to claim 6, wherein the openings are arranged such that the adjacent openings have a honeycomb shape.
The electromechanical transducer according to claim 2, wherein the opening is formed so that the shape increases as it is arranged from the center of the first vibration region toward the outer periphery.
The electromechanical converter according to claim 1, wherein an electric charge is injected into at least one of the vibration film and the fixed film, and an electret capacitor is configured by the vibration film and the fixed film.
Converting vibration of the vibrating membrane by sound pressure into an electrical signal,
A microphone comprising the electromechanical transducer according to claim 1.
A vibrating membrane having a first surface and a second surface opposite to the first surface, the first vibrating region and a second vibrating region disposed around the first vibrating region; A method of manufacturing an electromechanical transducer comprising a stationary membrane disposed opposite to the first surface of the vibrating membrane,
Forming a mesh-like groove on the surface of the substrate;
And a step of integrally forming, on the surface of the substrate and the groove, a reinforcing part that suppresses bending of the vibration film and the first vibration region of the vibration film.
The method of manufacturing an electromechanical converter according to claim 13, wherein the vibration film formed on the surface of the substrate, the side surface and the bottom surface of the groove portion, and the reinforcing portion have a uniform thickness.