WO2019083079A1

WO2019083079A1 - Electrostatic microphone

Info

Publication number: WO2019083079A1
Application number: PCT/KR2017/013127
Authority: WO
Inventors: 양기동; 박영진; 김선권; 조경환
Original assignee: 한국전기연구원
Priority date: 2017-10-23
Filing date: 2017-11-17
Publication date: 2019-05-02
Also published as: KR20190044905A

Abstract

A microphone according to the present invention comprises: a substrate; a barrier; a plurality of diaphragms positioned in the same space; an upper backplate arranged on the substrate so as to be spaced apart from the plurality of diaphragms at a predetermined interval; a connection structure for connecting the substrate and the plurality of diaphragms; an acoustic structure for converting, into a plane wave, a sound inputted from an external space; and a shared space encompassed by the plurality of diaphragms, the substrate, and the barrier. By using an electrostatic microphone structure, according to the present invention, a microphone exhibiting an improved directivity effect in a smaller size, in comparison with a conventional directional microphone, can be implemented. The structure can be easily applied to hearing aids, portable devices, IT/IoT devices, and the like and, particularly, to miniaturized devices.

Description

Static microphone

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to an electrostatic microphone, and more particularly, to an electrostatic microphone that exhibits improved directivity in a small size space.

A microphone is a device that receives a sound wave or an ultrasonic wave and generates an electric signal according to the vibration. Recently, as miniature wired and wireless equipments are continuously developed, the size of microphones is becoming smaller and smaller.

On the other hand, a directional microphone is a microphone capable of selectively recording only a narrow angle sound heard in a specific direction, and has a unidirectional microphone and a bidirectional microphone. Here, the directivity refers to a property that the sensitivity of the microphone varies depending on the directionality. Using the directional characteristic is the most effective way to selectively receive only the desired sound in a noisy environment.

Figure 1 illustrates a conventional structure for implementing a directional microphone. A method of implementing a conventional directional microphone implements directivity by arranging a plurality of microphones and delaying a signal output from the microphone to obtain a difference. In this case, a lot of space is required because a plurality of microphones should be arranged. When? R, which is a distance between the two microphones, is shorter than the wavelength of a sound wave, the size of the directivity output is reduced.

An object of the present invention is to provide a microphone in which the directivity characteristic is remarkably improved in a small-sized space.

According to an aspect of the present invention, there is provided a microphone including a substrate, a partition, a plurality of diaphragms disposed in the same space, an upper back plate disposed on the substrate and spaced apart from the plurality of diaphragms by a predetermined distance, A connection structure for connecting the substrate and the plurality of diaphragms, an acoustic structure for converting sound inputted from the external space into plane waves, and a common space surrounded by the plurality of diaphragms, the substrate, and the partition.

And further includes a lower back plate that supports the upper back plate and is connected to the plurality of diaphragms.

The plurality of diaphragms may include a first diaphragm and a second diaphragm, and the first diaphragm and the second diaphragm operate in cooperation with each other through the common space.

In addition, the first diaphragm and the second diaphragm are arranged such that the incident sound waves cause displacement of the first diaphragm to change the pressure of the common space, and the pressure of the changed common space limits the displacement of the second diaphragm .

The connection structure may be a wrinkle structure, a spring structure, or a patterned composite material thin film structure.

The acoustical structure may be a partition structure having a through hole or a partition structure having a pipe shape.

The microphone may further include a signal processing circuit for simultaneously or selectively extracting a directional and omnidirectional output.

Further, the upper back plate has a damping hole for adjusting a frequency response of the diaphragm.

The plurality of diaphragms may have a through hole for attenuating a pressure difference between the common space and the external space.

And is an electronic device including the microphone.

Through the electrostatic microphone structure of the present invention, a directional microphone whose size is reduced while maintaining the same SNR can be realized. Such a structure can be easily applied to a hearing aid, a portable device, an IT / Iot device, and particularly, a miniaturized device.

Also, instead of the frequency selective characteristic of the conventional resonance structure single element directional microphone, it is possible to have a directivity in a wide band.

However, the effects that can be achieved by the electrostatic microphone according to the embodiments of the present invention are not limited to those described above, and other effects not mentioned can be obtained from the following description, It will be clear to those who have.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

Figure 1 illustrates a conventional structure for implementing a directional microphone.

2 is a plan view showing a microphone according to a first embodiment of the present invention.

3 is a cross-sectional view taken along the line A-A 'of FIG.

FIG. 4A is a reference diagram for explaining a process of implementing directivity through a microphone according to the first embodiment of the present invention.

4B is a three-dimensional polar coordinate system for explaining the advantage of the acoustic structure for converting the external sound to the plane wave on the directivity.

5 is a cross-sectional view of a microphone according to a second embodiment of the present invention.

FIG. 6 is a reference diagram for explaining a process of implementing directivity through a microphone according to a second embodiment of the present invention.

7 is a cross-sectional view of a microphone according to a third embodiment of the present invention.

FIG. 8 is a reference diagram for explaining a process of implementing directivity through a microphone according to a second embodiment of the present invention.

FIG. 9 illustrates a wrinkle structure as an example of a connection structure according to an embodiment of the present invention.

10 illustrates a thin film pattern structure as an example of a connection structure according to an embodiment of the present invention.

Fig. 11 (a) shows a frequency response curve in the case where there is no connection structure, and Fig. 11 (b) shows a frequency response curve in the case where there is a connection structure.

FIG. 2 is a plan view showing a microphone according to a first embodiment of the present invention, and FIG. 3 is a sectional view taken along the line A-A 'of FIG.

2 is a plan view of the microphone with the partition wall removed. A substructure 100, an upper back plate 200A, a lower back plate 200B, a diaphragm 300, and a connection structure 400 are shown. Below the upper back plate 200A, the lower back plate 200B, the diaphragm 300, and the connection structure 400 are located on the same plane. The substrate 100 serves to support the above configurations.

The structure will be described in detail with reference to Fig. The microphone according to the present invention includes a substrate 100 serving as a support, a plurality of diaphragms 300 having a displacement in response to a sound change, a plurality of diaphragms 300 disposed on the substrate 100 and spaced apart from the plurality of diaphragms 300 by a predetermined distance The lower back plate 200B supporting the upper back plate 200A and the upper back plate 200A and being connected to the plurality of diaphragms, the substrate 100 and the plurality of diaphragms 300, A partition wall 500 having a plurality of through holes 510 for converting the sound inputted from the external space into a plane wave and a space formed below the plurality of diaphragms 300, And includes a common space 600 acoustically connecting the plurality of diaphragms 300 surrounded by the plurality of diaphragms 300, the substrate 100, and the partitions 500.

The substrate 100 serves to support the entire structure of the microphone. A back volume 600 surrounded by a plurality of diaphragms 300 and partition walls 500 is formed in the substrate 100. An upper back plate 200A is suspended on the substrate 100, do.

In the first embodiment, the lower back plate 200B for supporting the upper back plate 200A and connecting the plurality of diaphragms 300 is provided. However, the plurality of diaphragms 300 are not necessarily provided on the upper back plate 200A ) Or the lower back plate 200B, and the lower back plate 200B may not be provided in some cases.

In one embodiment, the substrate 100 may have silicon or a compound semiconductor. From a plan viewpoint, the common space 600 formed by a substrate or the like may be circular, but is not limited thereto.

In one embodiment, the substrate 100 is formed of one or more materials selected from the group consisting of germanium, silicon germanium, silicon carbide, gallium nitride, indium, indium gallium nitride ), Indium gallium arsenic, indium gallium zinc oxide, or other semiconductor materials and / or compound semiconductors.

One of the diaphragms 300 may be connected to the substrate 100 and the other of the diaphragms 300 may be connected to the lower back plate 200B through the connection structure 400. The upper back plate 200A may include a plurality of diaphragms 300, And can be spaced apart at a predetermined interval. The upper back plate 200A may have a back plate damping hole 210 for adjusting a frequency response of the plurality of diaphragms 300. [

On the other hand, to increase the sensitivity, it is required to increase the area of the diaphragm. However, increasing the area while using one diaphragm is very difficult to manufacture. The present invention is not limited to a single diaphragm, Respectively.

The diaphragm 300 and the upper back plate 200A may have a capacitance varying in size depending on the acoustic structure. And a signal acquisition circuit connected to the capacitance for amplifying and processing the signal.

The partition wall 500 basically serves to distinguish the external space from the common space 600. The barrier ribs 500 may be attached to the substrate 100. The barrier 500 may be formed in a structure that encapsulates or surrounds the microphone structure.

The barrier 500 may comprise various polymeric materials such as a composite thermosetting resin. Also, as one embodiment, the barrier 500 may be comprised of metal or may include a metal layer to provide electrostatic shielding. The thickness of barrier rib 500 may range from about 50 占 퐉 to about 500 占 퐉, preferably from 100 占 퐉 to 200 占 퐉, but is not limited thereto.

In the meantime, the microphone according to the present invention includes an acoustic structure for converting sound input from an external space into a plane wave. In the first embodiment, the acoustic structure is formed through the structure of the partition 500 having the through- Respectively.

The through holes 510 may be formed on both sides of the barrier 500, and the number of the through holes 510 formed on one side may be appropriately adjusted as necessary.

The microphone according to the present invention includes a plurality of diaphragms 300, a substrate 100, and a common space 600 surrounded by the partitions 500 below the plurality of diaphragms 300. The common space 600 acoustically connects the diaphragms to a space that is affected by both the movement of the first diaphragm 300A and the movement of the second diaphragm 300B. The plurality of diaphragms 300 may have a diaphragm through hole 310 for attenuating a pressure difference between the common space 600 and the external space. On the other hand, the common space may be formed on the upper side of the plurality of diaphragms.

Meanwhile, the signal processing circuit 700 may be connected to the substrate 100 by wire bonding. The signal processing circuit 700 may simultaneously or selectively extract a directional and an omnidirectional output.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor shall appropriately define the concept of the term in order to describe its invention in the best way It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It should be understood that various equivalents and modifications may be present. Hereinafter, an electrostatic microphone according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

What is to be detected as a directional signal in the directional microphone according to the present invention is the displacement difference between the first diaphragm 300A and the second diaphragm 300B. When the position of the sound source is located on the extension line of the line connecting the first diaphragm 300A and the second diaphragm 300B, a phase difference appears in the movement of the two diaphragms due to the time difference in arrival of the sound, A directional microphone with different response sizes can be implemented depending on the position.

The microphone according to the first embodiment of the present invention is an acoustic structure for converting an external sound into a plane wave, and has a through hole 510 in the partition 500. When the sound 800 is input from the external space through the through hole 510 provided in the partition wall 500, it is transformed into the plane wave 100. A high directivity response can be obtained by transforming the sound 800 of various properties inputted from the outside into the plane waves collectively through the through hole 510. [

4B is a three-dimensional polar coordinate system for explaining an advantage of the acoustic structure for converting the external sound to the plane wave on the directivity, and will be described in detail with reference thereto.

In detecting the direction of a sound source, the present invention using two microphones only detects the direction of a sound source on the xy-plane. This is because the microphone can detect only the angle (the angle indicated by phi in Fig. 4B) on the plane where the two diaphragms are located. The path difference from a sound source in arbitrary three-dimensional coordinates has a value proportional to cos (φ) * sin (θ). In this case, since there are two variables, the angle I can make mistakes in doing so. In order to solve this problem, when the sound wave of the space in which the two diaphragms are located is converted into a plane wave by using a structure (an acoustic structure for converting to a plane wave), the effect of the angle? Disappears and the position of the sound source can be grasped more accurately, It can be helpful in processing related signals.

Meanwhile, the plurality of diaphragms 300 according to the present invention may be composed of a first diaphragm 300A and a second diaphragm 300B as an embodiment. The first diaphragm 300A and the second diaphragm 300B are arranged in such a manner that the incident sound waves cause displacement of the first diaphragm 300A to change the pressure of the common space, May be arranged to limit the displacement of the diaphragm 300B, and may be arranged in order on the basis of the left side of the partition 500 on the same plane as an embodiment.

In the case where the sound 800 input from the outside is deformed into a plane wave and is incident, the sound wave first reaching the first diaphragm 300A moves the first diaphragm 300A, which changes the pressure of the common space 600 And the changed pressure of the common space 600 causes a force to be applied to the second diaphragm 300B so that a sound wave arriving late to the second diaphragm 300B hinders the movement of the second diaphragm 300B.

If the first diaphragm and the second diaphragm are operated in separate spaces, the two diaphragms operate independently without affecting each other. Conventionally, when the first diaphragm and the second diaphragm operate without being interlocked with each other, a signal about a phase difference caused by a difference in distance between two diaphragms is calculated. However, when two diaphragms operate in conjunction with each other as in the present invention, A signal obtained by adding an element that interferes with the movement of the second diaphragm 300B is obtained to the signal for the second diaphragm 300B. As a result, a larger signal can be obtained.

When there is a common space 600, a larger directivity response can be obtained than the existing structure without a common space. It is confirmed that the directional response increases up to 10 times compared with the conventional microphone array having no common space.

In order to obtain a larger signal when the two diaphragms operate in conjunction with each other, the pressure of the air present in the common space 600 must be sufficiently changed by the movement of the first diaphragm 300A But also the pressure of the changed air must be able to influence the movement of the second diaphragm 300B.

The air in the common space can be expressed by the spring coefficient of the vibrator. In order to influence the movement of the diaphragm, air in the common space is used as the diaphragm itself The spring coefficient k _air of the air in the common space must have a larger value than the structural spring coefficient k _str of the air space.

(1)

In the case of a conventional MEMS microphone, a diaphragm is formed of a thin film of a hard polysilicon or silicon nitride, and a considerable residual stress is present in the process of forming a thin film, so that the spring coefficient of the diaphragm structure is larger than the air spring coefficient , The size of the directivity response may not increase even if a common space is provided.

Accordingly, in the present invention, the connection structure 400 is implemented to reduce the spring coefficient due to the structure of the diaphragm. In one embodiment, the connection structure 400 may be a wrinkle structure, a spring structure, or a patterned composite material thin film structure.

FIG. 5 is a cross-sectional view of a microphone according to a second embodiment of the present invention, and FIG. 6 is a reference view for explaining a process of implementing directivity through a microphone according to the second embodiment.

Referring to FIG. 5, a second embodiment of the present invention includes a substrate 100 serving as a support, a plurality of diaphragms 300 having a displacement in accordance with acoustical changes, a plurality of diaphragms 300 disposed on the substrate 100, A connecting structure 400 connecting the upper back plate 200A, the substrate 100, and the plurality of diaphragms 300 spaced apart from each other by a predetermined distance, a plurality of through- A partition 500 having a plurality of diaphragms 300 and a plurality of diaphragms 300 and a plurality of diaphragms 300 disposed on the diaphragms 300. The plurality of diaphragms 300 includes a plurality of diaphragms 300, And includes a common space 600 acoustically connecting the plurality of diaphragms.

Second Embodiment Similarly to the first embodiment, the upper back plate 200A has the backplate through hole 210, the diaphragm 300 has the diaphragm through hole 310, the partition 500 has the partition through hole 510 And a signal processing circuit 700 may be provided.

However, the second embodiment differs from the first embodiment in that the common space 600 is formed on the upper side of the diaphragm 300 and does not have the lower back plate.

Meanwhile, FIG. 6 is a view for explaining a process of realizing directivity through a microphone according to the second embodiment, and the basic principle for implementing improved directivity is the same as the principle explained in the first embodiment.

FIG. 7 is a cross-sectional view of a microphone according to a third embodiment of the present invention, and FIG. 8 is a reference view for explaining a process of implementing directivity through a microphone according to the third embodiment.

Referring to FIG. 7, the third embodiment includes a substrate 100 serving as a support, a plurality of diaphragms 300 having a displacement in accordance with acoustical changes, a plurality of diaphragms 300 disposed on the substrate 100, A lower back plate 200B connected to the plurality of diaphragms, a substrate 100, and a connection structure 400 connecting the plurality of diaphragms 300. The upper back plate 200A, A plurality of diaphragms 300 and a plurality of diaphragms 300 may be disposed on the diaphragms 300. The diaphragms 300 may be divided into a plurality of diaphragms 300 and a plurality of diaphragms 300, acoustically connecting, and a common space 600.

Third Embodiment Similarly to the first embodiment, the upper back plate 200A includes the backplate through hole 210, the diaphragm 300 includes the diaphragm through hole 310, and the signal processing circuit 700 .

However, the partition wall 500, which is one component of the third embodiment, may be replaced with a partition wall structure in the form of a pipe. Through the structure of the pipe-shaped partition, sound input from the external space can be converted into plane waves.

Meanwhile, FIG. 8 is a view for explaining a process of implementing directivity through the microphone according to the third embodiment, and the basic principle for implementing improved directivity is the same as the principle explained in the first embodiment.

The connection structure 400 may be a wrinkle structure 410 as an example, and the wrinkle structure 410 may include a concave portion 410A and a convex portion 410B. The stress is concentrated in the concave portion 410A, that is, the corrugated region. As a result, stress is reduced in the area of the diaphragm 300 and the area of the convex part 410B. The corrugated structure 400 is connected to the diaphragm 300 to obtain an improved directivity response.

10 illustrates a connection structure having a compressive-tensile thin film pattern as an embodiment of the thin film pattern structure 420. Referring to FIG. As one embodiment of the connection structure, the process of forming the thin film pattern structure 420 is as follows.

A plasma chemical vapor deposition (PECVD) process is performed at a tensile strength of about 150 MPa to form a silicon nitride (SiN _x ) layer. A low pressure chemical vapor deposition (LPCVD) process is then performed at a tensile strength of about 1100 MPa to form a silicon nitride (SiN _x ) layer. And then compressed down to a strength of about 3000 MPa to form a thermal SiO _x layer. And the silicon nitride (SiN _x ) layer formed in the intermediate region 420D between the diaphragm 300 is removed.

The structure in the form of the thin film pattern serves as a connection structure to reduce the stress in the diaphragm 300 and the intermediate region 420D to obtain an improved directivity response.

Referring to FIG. 11A, when there is no connection structure, there is no significant difference in the size of a response between a structure having a separate back volume and a structure having a common back volume Can be confirmed.

Referring to FIG. 11 (b), when there is a connection structure, there is a significant difference in the size of the response between the structure having the separated back volume and the structure having the common back volume can confirm.

11 (a) and (b) show that the response size is larger in comparison with the case where there is no link structure in the case where there is a link structure basically. This is because the connection structure lowers the rigidity of the diaphragm, so that the diaphragm moves more (vibrates) even at the same pressure difference.

Although the directivity response size can be increased by introducing the connection structure, it is confirmed that the response size can be further increased if the common space is combined with the connection structure. This is because the common space induces the interaction between the movements of the two diaphragms, resulting in a larger response size. In order to maximize the effect, it is preferable that the rigidity of the diaphragm is sufficiently lowered so that the interaction between the diaphragms occurs smoothly.

In conclusion, if there is a connection structure, the residual stress becomes smaller and the response size itself becomes larger, and if there is a common space, an additional larger directivity response can be obtained.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, . Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the scope of the appended claims, as well as the appended claims.

Claims

Board;

septum;

A plurality of diaphragms located in the same space;

An upper back plate disposed on the substrate and spaced apart from the plurality of diaphragms by a predetermined distance;

A connection structure connecting the substrate and the plurality of diaphragms;

An acoustic structure for converting sound inputted from an external space into a plane wave; And

A common space surrounded by the plurality of diaphragms, the substrate, and the partition;

.
The method according to claim 1,

Further comprising a lower backplate supporting the upper backplate and connected to the plurality of diaphragms.
The method according to claim 1,

Wherein the plurality of diaphragms are composed of a first diaphragm and a second diaphragm, and the first diaphragm and the second diaphragm operate in cooperation with each other via the common space.
The method of claim 3,

Wherein the first diaphragm and the second diaphragm are arranged so that the incident sound waves cause displacement of the first diaphragm to change the pressure of the common space and that the pressure of the changed common space limits the displacement of the second diaphragm Features a microphone.
The method according to claim 1,

Wherein the connection structure is a wrinkle structure, a spring structure, or a patterned composite material thin film structure.
The method according to claim 1,

Wherein the acoustic structure is a diaphragm structure having a through hole or a diaphragm structure having a pipe shape.
The method according to claim 1,

Wherein the microphone further comprises a signal processing circuit for simultaneously or selectively extracting directional and omnidirectional outputs.
The method according to claim 1,

Wherein the upper back plate has a damping hole for adjusting the frequency response of the diaphragm.
The method according to claim 1,

Wherein the plurality of diaphragms have a through hole for attenuating a pressure difference between the common space and the external space.
An electronic device comprising a microphone according to any one of claims 1 to 9.