MEMS microphone

Abstract

Disclosed is a MEMS microphone, comprising: a substrate, a cavity being penetratingly provided in the substrate; a diaphragm, supported on the substrate and covering the cavity; a back plate, supported on the diaphragm, a first preset gap being formed between the back plate and the diaphragm; and a first support member, formed in the cavity, the first support member comprising a support portion spaced apart from the substrate and a connecting portion, the connecting portion extending from the support portion towards the substrate to be fixed to the substrate, the first support member further comprising a boss portion extending from the end of the support portion close to the diaphragm towards the diaphragm and supporting the diaphragm, and a second preset gap being formed between the diaphragm and the connecting portion in the vibration direction of the diaphragm. Compared with the existing technology, in the present invention, by means of providing the first support member to support the diaphragm, structural deformation of the diaphragm can be effectively prevented, and the firmness of the diaphragm is improved. When the impact force of a sound wave is too large, the diaphragm will not move significantly because the diaphragm is supported by the first support member, thereby preventing the diaphragm from being damaged.

Description

MEMS microphone TECHNICAL FIELD

[0001] The present application relates to the technical field of microphone, in particular to a MEMS microphone. BACKGROUND

[0002] In the prior art, the MEMS microphone comprises a substrate, a diaphragm arranged on the substrate, and a back plate arranged on the diaphragm, the diaphragm and the back plate constitute a capacitor as two electrode plates, when the diaphragm vibrates under the action of sound waves, the capacitance of the capacitor changes accordingly, so that the sound wave signal can be converted into an electric signal to realize the detection of the sound wave signal.

[0003] In the use process of the MEMS microphone, when the impact force of the sound wave is too large, the diaphragm is easily moved by a large amplitude, the diaphragm deviates by a large amplitude, and the diaphragm is damaged. TECHNICAL PROBLEM

[0004] The purpose of the present application is to provide a MEMS microphone to solve the technical problems in the prior art, which can prevent the diaphragm from being damaged due to the diaphragm deviating by a large amplitude. TECHNICAL SOLUTION

[0005] The present application provides a MEMS microphone, comprising:

[0006] a substrate, a cavity is arranged through the substrate;

[0007] a diaphragm supported on the substrate and covering the cavity;

[0008] a back plate supported on the diaphragm, a first predetermined gap is formed between the back plate and the diaphragm;

[0009] a first support formed in the cavity, the first support comprises a support portion spaced apart from the substrate and a connecting portion, the connecting portion extends from the support portion to the substrate, the first support further comprises a boss portion extending from one end of the support portion close to the diaphragm to support the diaphragm, and the diaphragm and the connecting portion form a second predetermined gap along the vibration direction of the diaphragm.

[0010] Preferably, the width of the second predetermined gap along the vibration direction is greater than or equal to 10μm.

[0011] Preferably, the boss portion is supported at the geometric center of the diaphragm.

[0012] Preferably, a second support is arranged between the back plate and the diaphragm, and the opposite ends of the second support are connected to the geometric centers of the back plate and the diaphragm, respectively.

[0013] Preferably, the support portion has a support portion bottom end away from the diaphragm in the vibration direction and a support portion top end close to the diaphragm, and from the support portion bottom end to the support portion top end, the width of the cross section of the support portion in the normal direction of the vibration direction of the diaphragm gradually linearly decreases.

[0014] Preferably, the connecting portion has a connecting portion bottom end away from the diaphragm in the vibration direction and a connecting portion top end close to the diaphragm, and from the connecting portion bottom end to the connecting portion top end, the width of the cross section of the connecting portion in the normal direction of the vibration direction of the diaphragm decreases.

[0015] Preferably, the cross section width size of the support portion satisfies the following formula: d1>2d0, wherein d1 represents the cross section width value of the support portion bottom end, and d0 represents half of the difference between the cross section width value of the support portion bottom end and the cross section width value of the support portion top end.

[0016] Preferably, the cross section width size of the connecting portion satisfies the following formula: d2<2d0, wherein d2 represents the cross section width value of the connecting portion bottom end, and d0 represents half of the difference between the cross section width value of the support portion bottom end and the cross section width value of the support portion top end.

[0017] Preferably, the connecting portion is provided with a plurality of connecting portions, and the plurality of connecting portions are annularly and spacedly arranged with the axis of the support portion in the vibration direction of the diaphragm as the center line.

[0018] Preferably, the connecting portion is provided with four connecting portions, and the included angle between two adjacent connecting portions is 90°. Beneficial effects

[0019] Compared with the prior art, the diaphragm is supported by the first support member, so that the structural deformation of the diaphragm can be effectively prevented, and the firmness of the diaphragm is improved. When the impact force of the sound wave is too large, the diaphragm will not move greatly due to being supported by the first support member, so that the diaphragm is prevented from being damaged. BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1 is a schematic view of the cross section structure of the whole structure of the present application in the normal direction of the vibration direction of the diaphragm;

[0021] Fig. 2 is a sectional view of A-A in Fig. 1;

[0022] Fig. 3 is a sectional view of B-B in Fig. 1;

[0023] Fig. 4 is a sectional view of C-C in Fig. 1;

[0024] Fig. 5 is a perspective view of the first support member of the present application when assembled on the base.

[0025] 10 - substrate, 20 - cavity, 30 - diaphragm, 40 - back plate, 50 - first preset gap, 60 - first support, 601 - support portion, 6011 - bottom end of support portion, 6012 - top end of support portion, 602 - connecting portion, 6021 - bottom end of connecting portion, 6022 - top end of connecting portion, 603 - boss portion, 70 - second preset gap, 80 - second support, 90 - first isolation layer, 100 - second isolation layer. Best Mode for Carrying Out the Invention

[0026] The embodiments described below are exemplary only, and are not to be construed as limiting the present application.

[0027] As shown in FIGS. 1-5, embodiments of the present application provide a MEMS microphone, comprising a substrate 10, a diaphragm 30, a back plate 40, and a first support 60, wherein:

[0028] The substrate 10 can be a silicon substrate, and a cavity 20 is provided through the substrate 10. Preferably, the inner profile surface of the cavity 20 is a circular groove structure.

[0029] The diaphragm 30 can be formed of polysilicon, and is supported on the substrate 10 and covers the cavity 20. In one possible embodiment, a first isolation layer 90 is further provided between the diaphragm 30 and the substrate 10. The first isolation layer 90 can be formed of phosphor silicon glass (PSG) or boron phosphor silicon glass (BPSG) by plasma enhanced chemical vapor deposition, and serves to support the diaphragm 30.

[0030] The back plate 40 can be formed of polysilicon, and is supported on the diaphragm 30. A first preset gap 50 is formed between the diaphragm 30 and the back plate 40. In one possible embodiment, a second isolation layer 100 is further provided between the diaphragm 30 and the back plate 40. The second isolation layer 100 can be formed of phosphor silicon glass (PSG) or boron phosphor silicon glass (BPSG) by plasma enhanced chemical vapor deposition, and serves to support the back plate 40.

[0031] Oppositely arranged electrodes on the back plate 40 and the diaphragm 30 form a capacitor. In response to pressure applied on the diaphragm 30, the distance between the diaphragm 30 and the back plate 40 changes, which results in a change in capacitance. Thus, sound wave signals can be converted into electrical signals, so that the sound wave signals can be detected.

[0032] The first support 60 is formed in the cavity 20, and the support includes a support portion 601 and a connecting portion 602 spaced apart from the base 10, and the support portion 601 and the connecting portion 602 are preferably integrally formed, or can be independently formed, which is not limited herein, the connecting portion 602 extends from the support portion 601 to the base 10, and the opposite ends of the connecting portion 602 are connected to the support portion 601 and the inner wall of the cavity 20, respectively, and the support portion 601 is fixed in the cavity 20 through the connecting portion 602.

[0033] The first support 60 further includes a boss portion 603 extending from one end of the support portion 601 close to the diaphragm 30 to the diaphragm 30 to support the diaphragm 30, and the boss portion 603 and the support portion 601 are preferably integrally formed, or can be independently formed, which is not limited herein, the boss portion 603 is supported on the side of the diaphragm 30 facing the cavity 20, which can effectively prevent the structural deformation of the diaphragm 30, improve the firmness of the diaphragm 30, and enable the diaphragm 30 to withstand a larger sound pressure, so that when the pressure applied to the diaphragm 30 is too large, the diaphragm 30 is limited to deviate in the direction of the cavity 20, thereby avoiding damage to the diaphragm 30.

[0034] Further, as shown in FIG. 4, the diaphragm 30 and the connecting portion 602 form a second preset gap 70 along the vibration direction of the diaphragm 30, and in the offset process, the connecting portion 602 does not limit the movement of the diaphragm 30, thereby ensuring the flexibility of the diaphragm 30, reducing the stiffness of the diaphragm 30, and improving the mechanical sensitivity of the MEMS microphone, and preferably, the width of the second preset gap 70 along the vibration direction is greater than or equal to 10 um.

[0035] In the embodiments provided by the present application, the boss portion 603 is supported at the geometric center of the diaphragm 30, and the central axis of the diaphragm 30 coincides with the central axis of the boss portion 603, and since the circumferential direction of the diaphragm 30 is connected to the first isolation layer 90 and the second isolation layer 100, the deflection thereof is parabolic, and the deflection is maximum at the center of the diaphragm 30 and decreases to zero at the edge. Since the sensitivity of the MEMS microphone is determined by the ratio of the change in capacitance with pressure, the boss portion 603 is arranged at the most intense place of the diaphragm 30, that is, the center of the diaphragm 30, and the connecting portion 602 and the diaphragm 30 also maintain the second preset gap 70, thereby reducing the stiffness of the diaphragm 30 and improving the sensitivity of the MEMS microphone.

[0036] Further, referring to FIGS. 2-4, a second support 80 is arranged between the back plate 40 and the diaphragm 30, the second support 80 can be formed of a silicon nitride layer, opposite ends of the second support 80 are respectively connected to the center of the back plate 40 and the diaphragm 30, the second support 80 is opposite to the boss portion 603, so that the diaphragm 30 can withstand a larger sound pressure, when the pressure applied to the diaphragm 30 is too large, the second support 80 limits the excessive displacement of the diaphragm 30 towards the side close to the back plate 40, thereby avoiding damage to the diaphragm 30.

[0037] In the embodiments provided by the present application, the support portion 601 is a structure with a width gradually decreasing in the direction from the cavity 20 to the back plate 40. In a feasible implementation, referring to FIG. 5, the support portion 601 is a column structure, the outer circumferential surface of the column structure gradually decreases in the direction from the cavity 20 to the back plate 40. Specifically, the support portion 601 has a support portion bottom end 6011 away from the diaphragm 30 in the vibration direction and a support portion top end 6012 close to the diaphragm 30, the end faces of the support portion bottom end 6011 and the support portion top end 6012 are circular, the support portion top end 6012 abuts against the boss portion 603, the width of the cross section of the support portion 601 in the normal direction of the vibration direction of the diaphragm 30 decreases in the direction from the support portion bottom end 6011 to the support portion top end 6012. In a feasible implementation, the outer contour surface of the boss portion 603 matches the outer contour surface of the support portion top end 6011, the cross-sectional width of the boss portion 603 is equal to the cross-sectional width of the support portion top end 6011.

[0038] Through the design of the gradually decreasing width size, the first support 60 not only plays a supporting role on the diaphragm 30, but also can avoid excessive influence on the flexibility of the diaphragm 30. When the pressure applied to the diaphragm 30 is too large, the first support 60 can limit the movement of the diaphragm 30, the diaphragm 30 moves around the boss portion 603, since the outer circumferential surface of the support portion 601 is an inclined surface, the probability of contact and collision between the diaphragm 30 and the outer surface of the support portion 601 is reduced, and the diaphragm 30 is better protected.

[0039] Further, referring to FIG. 3, the cross-sectional width of the support portion 601 satisfies the following formula: d1>2d0, d1 represents the cross-sectional width value of the support portion bottom end 6011, d0 represents half of the difference between the cross-sectional width value of the support portion bottom end 6011 and the cross-sectional width value of the support portion top end 6012.

[0040] In the embodiments provided by the present invention, the connecting part 602 is a structure with a gradually narrowing width along the direction from the cavity 20 to the back plate 40. Referring to FIG5, the connecting part 602 is a block structure. From the direction from the cavity 20 to the back plate 40, the outer peripheral surface of the block structure gradually narrows. The connecting part 602 has a bottom end 6021 away from the diaphragm 30 along the vibration direction and a top end 6022 close to the diaphragm 30. The end face of the bottom end 6021 and the end face of the top end 6022 are both rectangular. The distance between the diaphragm 30 and the end face of the top end 6022 is a second preset gap 70. The longitudinal section of the connecting part 602 is a trapezoidal surface. From the bottom end 6021 to the top end 6011, the width of the cross section of the connecting part 602 along the normal direction of the vibration direction of the diaphragm 30 gradually decreases linearly. The position of the connecting part 602 corresponding to the diaphragm 30 is reduced, which can avoid the diaphragm 30 from contacting and colliding with the side of the connecting part 602 during vibration and thus avoid failure.

[0041] Further, referring to Figures 2 and 3, the cross-sectional width of the connecting part 602 satisfies the following formula: d2 < 2d0, where d2 represents the cross-sectional width value of the bottom end 6021 of the connecting part, and d0 represents half of the difference between the cross-sectional width value of the bottom end 6011 of the support part and the cross-sectional width value of the top end 6012 of the support part.

[0042] In the embodiments provided by the present invention, as shown in FIG5, there are multiple connecting portions 602. The multiple connecting portions 602 are arranged in a ring with the axis of the support portion 601 along the vibration direction of the diaphragm 30 as the center line. Each connecting portion 602 is connected to the support portion 601 and the inner wall surface of the cavity 20, so that the support portion 601 can be more stably fixed in the cavity 20. When the MEMS microphone is subjected to a large impact force, the support portion 601 can always be supported at the center of the diaphragm 30 without displacement.

[0043] Preferably, there are four connecting parts 602, with the included angle between two adjacent connecting parts 602 being 90°, forming a cross-shaped structure. The support part 601 is located at the center of the cross-shaped structure. As those skilled in the art will know, the number of connecting parts 602 can also be set to other numbers, and the combined shape of each connecting part 602 can also be determined according to actual needs, such as a straight line, multiple parallel straight lines, a grid shape, a Y shape, etc. No limitation is made here.

[0044] Referring to FIG. 3 and FIG. 5, the inner wall surface of the cavity 20 is inclined to the vibration direction of the diaphragm 30, and the inclination angle of the inner wall surface of the cavity 20 can be determined according to actual conditions, which is not limited herein. Compared with the conventional technology in which the inner wall surface of the cavity 20 is parallel to the vibration direction of the diaphragm 30, in the embodiment provided by the present application, the inner wall surface of the cavity 20 is inclined, and the cavity 20 is wider near the diaphragm 30 than away from the diaphragm 30. The corresponding position of the cavity 20 and the diaphragm 30 is reduced, which can avoid the contact and collision failure of the diaphragm 30 with the inside of the cavity 20 when the diaphragm 30 vibrates.

[0045] Based on the MEMS microphone provided in the above embodiment, the present application further provides a manufacturing method, which comprises the following steps:

[0046] Step one, depositing a first isolation layer 90 on the substrate 10, and then forming the diaphragm 30 on the first isolation layer 90.

[0047] Step two, depositing a second isolation layer 100 on the diaphragm 30.

[0048] Step three, forming the back plate 40 on the second isolation layer 100. In step three, the second support 80 can be formed in the second isolation layer 100.

[0049] Step four, integrally forming the cavity 20 and the first support 60 in the substrate 10 below the diaphragm 30, for example, the cavity 20 and the first support 60 can be simultaneously formed in the substrate 10 by ion etching or chemical etching.

[0050] Step five, removing the first isolation layer 90 between the diaphragm 30 and the first support 60 by chemical etching, and simultaneously removing the second isolation layer 100 between the diaphragm 30 and the back plate 40, so as to form the first preset gap 50 between the back plate 40 and the diaphragm 30 and the second preset gap 70 between the diaphragm 30 and the connecting part 602.

[0051] In addition, by setting d1 as d1>2d0, it can be ensured that the second preset gap between the connecting part 605 of the first support 60 and the diaphragm 30 has sufficient distance when etching the first support 60, so as to reduce the noise generated when the diaphragm 30 vibrates, and improve the signal-to-noise ratio of the MEMS microphone.

[0052] In summary, the MEMS microphone provided in the embodiment of the present application is formed, which supports the diaphragm 30 by setting the first support 60, can effectively prevent the structural deformation of the diaphragm 30, and improve the firmness of the diaphragm 30. When the impact force of the sound wave is too large, the diaphragm 30 will not move greatly due to being supported by the first support 60, so as to avoid the damage of the diaphragm 30.

[0053] The above detailed description of the structure, features and effects of the present application is based on the embodiments shown in the drawings. The above description is only the preferred embodiments of the present application, but the present application is not limited to the embodiments shown in the drawings. Any changes or modifications made in accordance with the concept of the present application, or equivalent embodiments with equivalent changes, are still within the scope of the present application.

Claims

1. A MEMS microphone, characterized by, The application relates to a loudspeaker, comprising: a base provided with a cavity therein; a diaphragm supported on the base and covering the cavity; a back plate supported on the diaphragm, a first preset gap being formed between the back plate and the diaphragm; a first support formed in the cavity, the first support comprising a support portion spaced apart from the base and a connecting portion extending from the support portion towards the base and fixed to the base, and a boss portion extending from one end of the support portion close to the diaphragm towards the diaphragm and supporting the diaphragm, the diaphragm and the connecting portion forming a second preset gap along the vibration direction of the diaphragm.

2. The MEMS microphone of claim 1, wherein, The second preset gap has a width along the vibration direction of greater than or equal to 10 microns.

3. The MEMS microphone of claim 1, wherein, The boss portion is supported at the geometric center of the diaphragm.

4. The MEMS microphone of claim 1, wherein, A second support is arranged between the back plate and the diaphragm, and the second support is connected to the geometric center of the diaphragm and the back plate at opposite ends along the vibration direction of the diaphragm.

5. The MEMS microphone of claim 1, wherein, The support portion has a bottom end away from the diaphragm and a top end close to the diaphragm along the vibration direction, and the cross-sectional width of the support portion along the normal direction of the vibration direction of the diaphragm decreases from the bottom end to the top end.

6. The MEMS microphone of claim 5, wherein, The connecting portion has a bottom end away from the diaphragm and a top end close to the diaphragm along the vibration direction, and the cross-sectional width of the connecting portion along the normal direction of the vibration direction of the diaphragm decreases from the bottom end to the top end.

7. The MEMS microphone according to claim 6, characterized in that, The cross-sectional width of the support portion satisfies the formula d1>2d0, wherein d1 represents the cross-sectional width of the bottom end of the support portion, and d0 represents half of the difference between the cross-sectional width of the bottom end of the support portion and the cross-sectional width of the top end of the support portion.

8. The MEMS microphone of claim 6, wherein, The cross-sectional width of the connecting portion satisfies the formula d2<2d0, wherein d2 represents the cross-sectional width of the bottom end of the connecting portion, and d0 represents half of the difference between the cross-sectional width of the bottom end of the support portion and the cross-sectional width of the top end of the support portion.

9. The MEMS microphone of claim 1, wherein, The connecting portion is provided with a plurality of connecting portions, and the plurality of connecting portions are annularly spaced apart with the axis of the support portion along the vibration direction of the diaphragm as the center line.

10. The MEMS microphone according to claim 9, characterized in that, The connecting portion is provided with four connecting portions, and the included angle between two adjacent connecting portions is 90 degrees.

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