CN111147991A

CN111147991A - Capacitance microphone

Info

Publication number: CN111147991A
Application number: CN201911401899.7A
Authority: CN
Inventors: 但强; 李杨
Original assignee: AAC Acoustic Technologies Shenzhen Co Ltd
Current assignee: AAC Technologies Holdings Shenzhen Co Ltd
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2020-05-12
Anticipated expiration: 2039-12-30
Also published as: CN111147991B

Abstract

The invention provides a capacitance microphone, which comprises a fixed support, a vibration part and an elastic connecting part, wherein the elastic connecting part is connected between the vibration part and the fixed support and supports the vibration part; the fixed support is provided with a containing part; the vibration part is suspended and supported in the accommodating part; the fixed support comprises a fixed part and a fixed electrode which surround the accommodating part, the vibrating part comprises a supporting part and a moving electrode, the fixed electrode and the moving electrode are arranged in a comb-tooth shape, and the fixed electrode and the moving electrode are separated in space and are mutually crossed to form a capacitance structure; the elastic connecting parts are respectively arranged on two opposite sides of the capacitor structure, one side of each elastic connecting part is connected with the fixing part, and the other side far away from the fixing part is connected with the supporting part; and the supporting part, the fixing part and the elastic connecting parts positioned on the two opposite sides of the capacitor structure are enclosed to form a sealed cavity, and the fixed electrode and the moving electrode are positioned in the sealed cavity. The invention realizes the great reduction of the damping of the relative movement by sealing at least the relative movement gap between the fixed electrode and the movable electrode in a low-pressure area (less than atmospheric pressure), thereby achieving the purpose of improving the signal-to-noise ratio (SNR).

Description

Capacitance microphone

[ technical field ] A method for producing a semiconductor device

The invention relates to the field of capacitive sound-electricity conversion.

[ background of the invention ]

The typical core structure of the condenser microphone is a plate capacitor, which mainly comprises a back plate and a diaphragm, wherein the diaphragm vibrates under an external sound pressure signal, and the sound pressure change is indirectly measured by detecting the capacitance value changed between the back plates of the diaphragm. As the use and products of the condenser microphone are continuously updated, the demand for the key performance of the condenser microphone is continuously increased, especially the signal-to-noise ratio (SNR) index.

The main factor determining the SNR is the air damping in the microphone structure. Aiming at a flat capacitor structure, the air damping form is mainly die damping, and the reduction of the die damping can be realized by preparing a through hole array on a back plate. The proportion of through holes in the existing design is up to 70% or more, and the extreme results are achieved in the design, so that the research on comb capacitor structures, vacuum packaging and other technologies are turned to for further improving the SNR index.

The typical design of the comb-tooth type condenser microphone comprises a fixed support and a vibration part, the fixed support comprises a fixed part and fixed comb teeth connected with the fixed part, the vibration part comprises a support part and movable comb teeth connected with the support part, the fixed comb teeth and the movable comb teeth are separated in space and mutually crossed, the relative movement mode between the comb teeth is slippage, the magnitude of the damping of a sliding film is smaller than that of a pressing film, and the possibility is provided for the design of the condenser microphone with high signal-to-noise ratio.

[ summary of the invention ]

The invention aims to provide a capacitance microphone, aiming at improving the signal-to-noise ratio.

The technical scheme of the invention is as follows:

a condenser microphone comprising:

the fixed support is provided with a containing part;

a vibrating portion suspended and supported within the receiving portion; and

an elastic connecting part connected between the vibration part and the fixed support and supporting the vibration part;

the fixed support comprises a fixed part surrounding the accommodating part and a fixed electrode extending from the edge of the fixed part to the vibrating part, the vibrating part comprises a supporting part arranged at an interval with the fixed part and a movable electrode extending from the supporting part to the fixed part, the fixed electrode and the movable electrode are both arranged in a comb-tooth shape, the fixed electrode and the movable electrode are separated in space, and the fixed electrode and the movable electrode are crossed with each other to form a capacitance structure;

one side of the elastic connecting part is connected with the fixing part, and the other side of the elastic connecting part, which is far away from the fixing part, is connected with the supporting part; the elastic connecting parts are respectively arranged on two opposite sides of the capacitor structure, the supporting part, the fixing part and the elastic connecting parts positioned on two opposite sides of the capacitor structure enclose a sealed cavity, and the fixed electrode and the moving electrode are positioned in the sealed cavity.

Furthermore, each elastic connecting part comprises a film, a first supporting wall and a second supporting wall, wherein the film is opposite to the capacitor structure and is arranged at intervals, the first supporting wall extends from one side, close to the fixing part, of the film in a bending mode, and the second supporting wall extends from one side, close to the supporting part, of the film in a bending mode towards the supporting part.

Further, the film is provided with a strip-shaped groove, and the extending direction of the strip-shaped groove is parallel to the first supporting wall and the second supporting wall.

Further, the section of the strip-shaped groove on the section perpendicular to the extending direction is square, triangular function, triangular or trapezoidal.

Furthermore, a stress layer is arranged on the film, and the stress value of the stress layer is 10 MPa-1500 MPa.

Further, the thickness of the stress layer is less than or equal to 20 microns.

Furthermore, the supporting part is provided with a vent hole.

Furthermore, the supporting part is provided with a supporting rib reinforcing rib in an attaching mode.

Further, the fixed part is the annular duplex winding and locates the supporting part periphery, the fixed part is including relative last side and the downside that sets up and being connected the medial surface of last side and downside, decide the electrode certainly the medial surface of fixed part extends.

Further, the thickness of the support portion in the vibration direction of the vibration portion is smaller than or equal to the thickness of the moving electrode in the vibration direction.

Further, the shape of the fixing portion and the shape of the supporting portion are both symmetrical about the center.

The invention has the beneficial effects that: the gap between the fixed electrode and the movable electrode is sealed in a low-pressure area, so that the damping of the relative motion of the fixed electrode and the movable electrode can be greatly reduced, and the aim of improving the signal-to-noise ratio (SNR) is fulfilled.

[ description of the drawings ]

Fig. 1 is a schematic structural diagram of a condenser microphone according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1;

FIG. 3 is a cross-sectional view taken along line B-B of FIG. 1;

fig. 4 is a schematic structural diagram of a condenser microphone according to another embodiment of the present invention;

FIG. 5 is a cross-sectional view taken along line C-C;

fig. 6 is a schematic structural diagram of a condenser microphone according to another embodiment of the present invention;

FIG. 7 is a cross-sectional view taken along line D-D;

fig. 8 is a schematic structural diagram of a condenser microphone according to another embodiment of the present invention;

FIG. 9 is a cross-sectional view taken along line E-E;

fig. 10 is a schematic structural diagram of a condenser microphone according to yet another embodiment of the present invention;

FIG. 11 is a sectional view taken along line F-F;

FIG. 12 is a finite element cloud of deformation caused by a stress layer in a condenser microphone according to the present invention;

FIG. 13 is a finite element cloud (without a bar groove) of the deformation caused by the stress layer in the condenser microphone according to the present invention;

FIG. 14 is a graph showing the relationship between the stress value and the displacement difference of the stress layer in the condenser microphone according to the present invention.

In the figure:

100. a condenser microphone; 1. fixing a support; 2. a vibrating section; 3. an elastic connection portion; 11. a fixed part; 12. fixing an electrode; 21. a support portion; 22. a moving electrode; 30. sealing the cavity; 31. a first support wall; 32. a second support wall; 33. a film; 4. a strip-shaped groove; 5. a stress layer; 6. a vent hole; 7. and (5) reinforcing ribs.

[ detailed description ] embodiments

The invention is further described with reference to the following figures and embodiments.

Referring to fig. 1 to 11, a condenser microphone 100 includes:

the fixed support 1 is provided with an accommodating part;

a vibration part 2, wherein the vibration part 2 is suspended and supported in the accommodating part; and

an elastic connecting part 3 connected between the vibration part 2 and the fixed support 1 and supporting the vibration part 2;

the fixed support 1 comprises a fixed part 11 surrounding the accommodating part and a fixed electrode 12 extending from the edge of the fixed part 11 to the vibrating part 2, the vibrating part 2 comprises a supporting part 21 arranged at a distance from the fixed part 11 and a movable electrode 22 extending from the supporting part 21 to the fixed part 11, the fixed electrode 12 and the movable electrode 22 are arranged in a comb-tooth shape, the fixed electrode 12 is spatially separated from the movable electrode 22, and the fixed electrode 12 and the movable electrode 22 are crossed with each other to form a capacitance structure;

one side of the elastic connecting part 3 is connected with the fixing part 11, and the other side far away from the fixing part 11 is connected with the supporting part 21; the elastic connection portion 3 is respectively disposed on two opposite sides of the capacitor structure, the support portion 21, the fixing portion 11 and the elastic connection portion 3 disposed on two opposite sides of the capacitor structure enclose a sealed cavity 30, and the fixed electrode 12 and the movable electrode 22 are disposed in the sealed cavity 30.

When the vibrating part 2 vibrates under the action of sound waves, the fixed electrode 12 and the movable electrode 22 move relatively to generate electric charge output, so that sound wave signals are converted into electric signals, and the corresponding function of the microphone is realized. Because the gap between the fixed electrode 12 and the movable electrode 22 is sealed in a low-pressure area, the damping can be greatly reduced, thereby achieving the purpose of improving the signal-noise ratio SNR.

Preferably, each of the elastic connection portions 3 includes a film 33 opposite to the capacitor structure and disposed at an interval, a first support wall 31 extending from one side of the film 33 close to the fixing portion 11 in a bending manner, and a second support wall 32 extending from one side of the film 33 close to the support portion 21 in a bending manner. The supporting portion 21, one of the first supporting arms, one of the films 33, one of the second supporting arms, the fixing portion 11, the other of the second supporting arms, the other of the films 33, and the other of the first supporting arms sequentially enclose the sealed cavity 30.

Referring to fig. 10 and 11, preferably, the film 33 is provided with a strip-shaped groove 4, and an extending direction of the strip-shaped groove 4 is parallel to the first supporting wall 31 and the second supporting wall 32. Referring to fig. 8 and 9, the portion of the film 33 with the strip-shaped grooves 4 forms a corrugated structure, which can reduce the rigidity by making the corrugated structure, and is beneficial to the sound pressure action to move the comb teeth to deform, and the corrugated structure can be: square wave, sine wave, triangular wave, trapezoidal wave, etc., the two membranes 33 may be formed with a strip-shaped groove 4.

Preferably, the cross-sectional shape of the strip-shaped groove 4 on the cross section perpendicular to the extending direction is a square shape, a trigonometric function shape, a triangle shape or a trapezoid shape.

Referring to fig. 4 to 11, a stress layer 5 is preferably disposed on the film 33, and the stress value of the stress layer 5 is 10MPa to 1500 MPa. The stress layer 5 may be one layer or multiple layers, and the stress layer 5 may be prepared by processes such as Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), sputtering, evaporation, epitaxy, and the like, and the material may be polysilicon, silicon nitride, silicon carbide, metal, and the like. Further referring to fig. 12-14, fig. 12 and 13 both show finite element cloud diagrams of deformation caused by the stress layer 5, where fig. 12 and 13 are different in that the stress layer 5 has a strip-shaped groove 4, the amplitude is larger when stressed, and decreases from left to right when viewed from the figure, in fig. 12, the voltage corresponding to the maximum amplitude is 5.403e-03, the driving voltage for no displacement on the right side is 0, in fig. 13, the voltage corresponding to the maximum amplitude is 2.726e-03, the driving voltage for no displacement on the right side is 0, fig. 14 is a graph of the relationship between the stress value in the stress layer 5 and the displacement difference of the fixed electrode, where the abscissa represents the stress value in the stress layer 5, the ordinate represents the displacement difference of the fixed electrode, where the dotted line represents the structure in which the strip-shaped groove 4 is formed in the film 33, and the solid line represents the structure in which the film 33 is not formed with the strip-.

The stress layer 5 preferably has a thickness of 20 μm or less. The stress layer 5 is also less stiff at small thicknesses, so that the elasticity of the membrane 33 is not affected.

Referring to fig. 6 and 7, preferably, the support portion 21 is provided with a vent hole 5, and the vent hole 5 can improve low frequency attenuation, as shown in fig. 4 and 5.

It is preferable that the thickness of the support portion 21 in the vibration direction of the vibrating portion 2 is smaller than or equal to the thickness of the moving electrode 22 in the vibration direction. Thus, material can be saved and acoustic resistance can be reduced.

With continued reference to fig. 6 and 7, the support portion 21 is preferably affixed with ribs 6, and the ribs 6 can ensure strength with a slight increase in mass of the vibrating portion 2, resulting in less out-of-plane deformation, similar to piston motion, as shown in fig. 4 and 5.

Preferably, the supporting portion 21 includes an upper surface and a lower surface which are oppositely disposed, and the stiffener 6 is fixed to the lower surface, so as to further enhance the supporting function of the stiffener 6, specifically referring to fig. 4 and 5, it is noted that the piezoelectric microphone is shown upside down in the drawings, so that the lower surface is located at the upper side.

Preferably, the fixing portion 11 is annular and is wound on the periphery of the supporting portion 21, the fixing portion 11 includes an upper side and a lower side which are oppositely arranged and an inner side which is connected with the upper side and the lower side, and the fixed electrode 12 extends from the inner side of the fixing portion 11. The movable electrode 22 extends from the outer side surface of the support portion 21, and the fixing portion 11 is formed in a ring shape, so that the support portion 21 has better stability when vibrating.

Preferably, the shape of the fixing portion 11 and the shape of the supporting portion 21 are symmetrical with respect to the center, and correspondingly, the structure of the reinforcing ribs 6 and the distribution of the vent holes 5 are symmetrically distributed with respect to the center, so that the overall structural stability and uniformity are good.

Preferably, the fixing portion 11 and the supporting portion 21 are both circular or both square.

Preferably, the fixed electrode 12 extends from two opposite sides of the fixed portion 11, and particularly referring to fig. 1-3, the fixed electrode 12 and the movable electrode 22 may not be formed over the entire annular boundary.

While the foregoing is directed to embodiments of the present invention, it will be understood by those skilled in the art that various changes may be made without departing from the spirit and scope of the invention.

Claims

1. A condenser microphone, comprising:

the fixed support is provided with a containing part;

a vibrating portion suspended and supported within the receiving portion; and

2. The condenser microphone of claim 1, wherein: each elastic connecting part comprises a film, a first supporting wall and a second supporting wall, wherein the film is opposite to the capacitor structure and is arranged at intervals, the first supporting wall is arranged on one side, close to the fixing part, of the film, the fixing part is bent and extended, and the second supporting wall is arranged on one side, close to the supporting part, of the film, and is bent and extended towards the supporting part.

3. The condenser microphone of claim 2, wherein: the film is provided with a strip-shaped groove, and the extension direction of the strip-shaped groove is parallel to the first supporting wall and the second supporting wall.

4. A condenser microphone as claimed in claim 3, wherein: the section of the strip-shaped groove on the section perpendicular to the extending direction is square, trigonometric function, triangular or trapezoidal.

5. The condenser microphone of claim 2, wherein: the film is provided with a stress layer, and the stress value of the stress layer is 10 MPa-1500 MPa.

6. The condenser microphone of claim 5, wherein: the stress layer has a thickness less than or equal to 20 microns.

7. The condenser microphone of claim 1, wherein: the supporting part is provided with a vent hole.

8. The condenser microphone of claim 1, wherein: the thickness of the supporting part along the vibration direction of the vibration part is smaller than or equal to the thickness of the moving electrode along the vibration direction.

9. The condenser microphone of claim 1, wherein: and reinforcing ribs are arranged on the supporting parts.

10. The condenser microphone of claim 1, wherein: the fixed part is the annular duplex winding and locates the supporting part periphery, the fixed part is including relative last side and the downside and be connected of setting up the medial surface of last side and downside, decide the electrode certainly the medial surface of fixed part extends.

11. The condenser microphone of claim 1, wherein: the shape of the fixing portion and the shape of the supporting portion are both symmetrical about the center.