Dual-diaphragm silicon microphone and manufacturing method thereof

Abstract

The present invention relates to a dual-diaphragm silicon microphone and a method for manufacturing the same. The microphone comprises a lower structural layer, a first diaphragm, a back plate, a second diaphragm, a first cavity, a first sacrificial layer anchoring area, a second cavity, a second sacrificial layer anchoring area, a third cavity, a third sacrificial layer anchoring area, a through hole, a gas flow channel, a connecting rod, a release hole, and a cavity sealing structure. The manufacturing method comprises the following steps: sequentially depositing a first sacrificial layer, a first diaphragm, and a second sacrificial layer on the lower structural layer; depositing the back plate and patterning it to form a through hole; depositing the third sacrificial layer and patterning it to form a deep groove; depositing a connecting rod film layer and patterning it; depositing the second diaphragm and patterning it to form a release hole; releasing the second and third sacrificial layers; depositing a sealing material and patterning it to form a cavity sealing structure; photolithographically etching the back of the lower structural layer and stopping at the first sacrificial layer to form a gas flow channel; and corroding and releasing part of the material of the first sacrificial layer to form a first cavity.

Description

Technical Field

[0001] The present invention relates to the field of silicon microphones, and in particular to a dual-diaphragm silicon microphone and a manufacturing method thereof. Background Art

[0002] MEMS (micro-electromechanical system) microphones, also known as silicon microphones, are widely used in popular consumer applications such as mobile phones, headphones, and speakers, as well as in emerging areas such as smart homes, the Internet of Things, wearable devices, VR, and AR, due to their small size, good consistency, suitability for mass production, and surface mountability. In the practical application of silicon microphones, signal-to-noise ratio is a key performance parameter. With the continuous emergence of high-end applications, improving this ratio is currently a focus of the industry.

[0003] At present, how to break through the performance limits caused by the limited size of MEMS microphones and develop MEMS microphones with smaller size, higher signal-to-noise ratio and larger acoustic overload point has very important research and commercial value, and is of great significance for China's MEMS manufacturing industry to move towards high-end. Summary of the Invention

[0004] The object of the present invention is to overcome the problem of poor signal-to-noise ratio of existing silicon microphones, thereby providing a dual-diaphragm silicon microphone and a manufacturing method thereof.

[0005] In order to solve the above technical problems, the technical solution of the present invention provides a dual-diaphragm silicon microphone, wherein the microphone structure body comprises, from bottom to top, a lower structure layer 7, a first diaphragm 5, a back plate 3, and a second diaphragm 1;

[0006] A first cavity 8 and a first sacrificial layer anchoring area 6 are provided between the lower structural layer 7 and the first diaphragm 5; a second cavity 9 and a second sacrificial layer anchoring area 4 are provided between the first diaphragm 5 and the back plate 3; the first cavity 8 and the second cavity 9 are used to provide movement space for the first diaphragm 5; a third cavity 15 and a third sacrificial layer anchoring area 2 are provided between the back plate 3 and the second diaphragm 1; the third cavity 15 is used to provide movement space for the second diaphragm 1;

[0007] A through hole 13 is provided in the middle of the back plate 3, and the through hole 13 is used to connect the second cavity 9 and the third cavity 15;

[0008] The lower structural layer 7 is provided with a gas flow channel 10;

[0009] A connecting rod 14 is provided between the first diaphragm 5 and the second diaphragm 1 , and the connecting rod 14 passes through the through hole 13 to connect the first diaphragm 5 and the second diaphragm 1 , so as to enable the first diaphragm 5 and the second diaphragm 1 to move synchronously;

[0010] A release hole 12 is provided on the second diaphragm 1 , and a cavity sealing structure 11 is provided on the release hole 12 .

[0011] As one of the improvements of the above technical solution, the back plate 3 is configured as a multi-layer composite layer, including a conductive layer 3-1 and other layers as structural layers 3-2;

[0012] When the back plate 3 adopts two composite layers, the following situations are included:

[0013] The lower layer is the back plate structural layer 3-2, and the upper layer is the back plate conductive layer 3-1;

[0014] The upper layer is the back plate structural layer 3-2, and the lower layer is the back plate conductive layer 3-1;

[0015] When the back plate 3 adopts a three-layer composite layer, the following situations are included:

[0016] The upper and lower layers are the back plate structural layer 3-2, and the middle layer is the back plate conductive layer 3-1;

[0017] The upper and lower layers are the back plate structure layer 3-2, the middle layer is the back plate conductive layer 3-1, and the sidewalls of the back plate conductive layer 3-1 are covered by the back plate structure layer 3-2;

[0018] The back plate conductive layer 3 - 1 is a conductor material, including polysilicon or amorphous silicon material; the back plate structural layer 3 - 2 is an insulating material, including silicon nitride material.

[0019] As one of the improvements of the above technical solution, a release stop structure 16 is provided on the inner and outer sides of the first sacrificial layer anchor area 6, the second sacrificial layer anchor area 4, and the third sacrificial layer anchor area 2 to control the boundaries of the first sacrificial layer anchor area 6, the second sacrificial layer anchor area 4, and the third sacrificial layer anchor area 2.

[0020] As one of the improvements of the above technical solution, the release stop structure 16 is further provided on the outer side of the back plate 3 to control the boundary of the back plate 3 .

[0021] As one of the improvements of the above technical solution, the release stop structure 16 is also provided on the outside of the first diaphragm 5 to control the boundary of the first diaphragm 5 .

[0022] As one of the improvements of the above technical solution, the upper and lower surfaces of the connecting rod 14 are electrically insulated.

[0023] As one of the improvements of the above technical solution, the material of the first sacrificial layer anchor region 6, the second sacrificial layer anchor region 4, and the third sacrificial layer anchor region 2 is a single material of silicon oxide, borosilicate glass, phosphosilicate glass, or borophosphosilicate glass, or a composite material of at least two of them randomly stacked;

[0024] The material of the first diaphragm 5 and the second diaphragm 1 is polycrystalline silicon or amorphous silicon;

[0025] The material of the lower structural layer 7 is silicon;

[0026] The connecting rod 14 is made of either a single silicon nitride material or a composite material comprising a random stack of silicon nitride, polycrystalline silicon, and / or amorphous silicon. Silicon nitride is an insulating material, so the connecting rod is made of silicon nitride or a composite material of silicon nitride, polycrystalline silicon, or silicon nitride and amorphous silicon. This means that if silicon nitride is used alone, it is insulating. If a composite material is used, even if the polycrystalline silicon or amorphous silicon is conductive, the silicon nitride between them still insulates the connecting rod from top to bottom.

[0027] The present invention also provides a method for manufacturing any of the above-mentioned dual-diaphragm silicon microphones, comprising the following steps:

[0028] 1) depositing a first sacrificial layer on the lower structural layer 7;

[0029] 2) depositing a first diaphragm 5 on the first sacrificial layer;

[0030] 3) depositing a second sacrificial layer on the first diaphragm 5;

[0031] 4) depositing a back plate 3 on the second sacrificial layer and patterning to form one or more through holes 13;

[0032] 5) depositing a third sacrificial layer on the back plate 3;

[0033] 6) Patterning to form a deep groove for subsequent deposition of the film material for the connecting rod 14, with the deep groove extending all the way to the surface of the first diaphragm 5, depositing the film layer for the connecting rod 14, and patterning to form the connecting rod 14; or, after the deposition in steps 3), 4), and 5) is completed, patterning is performed separately to form a partial structure of the connecting rod 14, and the connecting rod 14 is formed layer by layer;

[0034] 7) depositing a second diaphragm 1 on the third sacrificial layer and patterning a release hole 12, completing the etching release of the second and third sacrificial layers through the release hole 12, thereby forming a second sacrificial layer anchor region 4, a third sacrificial layer anchor region 2, a second cavity 9, and a third cavity 15;

[0035] 8) Depositing a sealing material for the release hole 12 on the second diaphragm 1 and patterning it to form a cavity sealing structure 11;

[0036] 9) Photolithographic etching of the back side of the lower structural layer 7, stopping at the first sacrificial layer, to form a gas flow channel 10;

[0037] 10) Etching to release part of the material of the first sacrificial layer to form a first cavity 8 and a first sacrificial layer anchor region 6 .

[0038] As one of the improvements to the above technical solution, when the release stop structure 16 is provided on the inner and outer sides of the first sacrificial layer anchor area 6, the second sacrificial layer anchor area 4, and the third sacrificial layer anchor area 2, the specific steps are further included: after the deposition of the first, second, and third sacrificial layers in steps 1), 3), and 5) is completed, the sacrificial layers are patterned to form grooves, and then an anchor area release stop material is deposited to pattern the anchor area release stop structure 16;

[0039] When a release stop structure 16 is provided on the inner and outer sides of the first sacrificial layer anchor area 6, the second sacrificial layer anchor area 4, the third sacrificial layer anchor area 2, and the outer side of the back plate 3, the specific steps are further included: after the deposition of the first and second sacrificial layers, the back plate 3, and the third sacrificial layer is completed in steps 1), 3), 4), and 5), the back plate and each sacrificial layer are patterned to form a groove, and then an anchor area release stop material is deposited to pattern the anchor area release stop structure 16;

[0040] When a release stop structure 16 is provided on the inner and outer sides of the first sacrificial layer anchor area 6, the second sacrificial layer anchor area 4, and the third sacrificial layer anchor area 2, as well as on the outer sides of the first diaphragm 5 and the back plate 3, the specific steps are further included: after the deposition of the first sacrificial layer, the first diaphragm 5, the second sacrificial layer, the back plate 3, and the third sacrificial layer is completed in steps 1), 2), 3), 4), and 5), the first diaphragm 5, the back plate 3, and the sacrificial layers are patterned to form grooves, and then an anchor area release stop material is deposited to pattern the anchor area release stop structure 16;

[0041] The release stop structure 16 is made of polysilicon, amorphous silicon, or silicon nitride.

[0042] As one of the improvements of the above technical solution, the deposition method of the first sacrificial layer is: thermal oxidation or chemical vapor deposition CVD;

[0043] The deposition method of the second sacrificial layer, the third sacrificial layer, the first diaphragm 5, the second diaphragm 1, the back plate 3 and the deposition method of the release hole sealing material on the second diaphragm 1 are CVD;

[0044] The CVD includes: low pressure chemical vapor deposition LPCVD, atmospheric pressure chemical vapor deposition APCVD, sub-atmospheric pressure chemical vapor deposition SACVD, plasma enhanced chemical vapor deposition PECVD;

[0045] The etching release of the first sacrificial layer, the second sacrificial layer and the third sacrificial layer is achieved by wet etching with a hydrofluoric acid HF solution, a buffered oxide etchant BOE solution or vapor-phase hydrofluoric acid Vapor-phase HF etching.

[0046] The advantages of the present invention are that the dual-diaphragm silicon microphone proposed in the present invention has the following advantages:

[0047] 1. The first diaphragm, the second diaphragm, the sealing structure, and the edge anchor area form a closed constant pressure cavity with minimal long-term pressure changes, improving the device's signal-to-noise ratio and other performance;

[0048] 2. The back plate adopts a composite layer structure design to improve structural reliability;

[0049] 3. The connecting rod between the first diaphragm and the second diaphragm is formed by a composite stack of multiple layers of materials. Each layer of material has good flatness, which makes it easy to increase the cross-sectional area of ​​the connecting rod and improve the strength. Each layer is patterned in sequence, which facilitates flexible control of the gap between the connecting rod and the back plate through-hole, and can achieve a small gap design, thereby improving the chip area utilization;

[0050] 4. The anchor zone releases the stop structure to precisely control the cavity boundary;

[0051] 5. Better, the connecting rod part uses stress matching of silicon oxide and silicon nitride to reduce the impact of the connecting rod residual stress on the diaphragm, reduce film deformation, and make the diaphragm smoother, more sensitive, more consistent, and have a better yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a schematic cross-sectional view of the dual-diaphragm silicon microphone structure of the present invention;

[0053] Figure 2 and Figure 3 This is a cross-sectional schematic diagram of the double-layer composite back plate of the present invention, wherein Figure 2 The upper layer of the back plate is the conductive layer. Figure 3 The lower layer of the back plate is a conductive layer;

[0054] Figure 4 Schematic cross-sectional view of the three-layer composite back electrode plate of the present invention;

[0055] Figure 5 This is a cross-sectional schematic diagram of the three-layer composite back electrode plate of the present invention, in which the sidewall of the conductive layer is covered by the back electrode plate structure layer;

[0056] Figure 6 For connecting rod structure matching Figure 2 A schematic cross-sectional view of an embodiment of the back plate shown;

[0057] Figure 7 For connecting rod structure matching Figure 3 A schematic cross-sectional view of an embodiment of the back plate shown;

[0058] Figure 8 For connecting rod structure matching Figure 4 A schematic cross-sectional view of an embodiment of the back plate shown;

[0059] Figure 9 For connecting rod structure matching Figure 5 A schematic cross-sectional view of an embodiment of the back plate shown;

[0060] Figure 10 A schematic cross-sectional view of an embodiment of the present invention with two release holes and a sealing structure

[0061] Figure 11 It is a cross-sectional schematic diagram of an embodiment of the present invention in which release stop structures are provided on the inner and outer sides of the first sacrificial layer anchor region, the second sacrificial layer anchor region, and the third sacrificial layer anchor region;

[0062] Figure 12 A cross-sectional schematic diagram of an embodiment of the present invention in which a release stop structure is provided on the inner and outer sides of the first sacrificial layer anchor region, the second sacrificial layer anchor region, the third sacrificial layer anchor region, and the outer side of the back plate;

[0063] Figure 13 A cross-sectional schematic diagram of an embodiment of the present invention in which release stop structures are provided on the inner and outer sides of the first sacrificial layer anchor area, the second sacrificial layer anchor area, the third sacrificial layer anchor area, and the outer sides of the first diaphragm and the back plate;

[0064] Figure 14 A schematic cross-sectional view of an embodiment of the present invention in which multiple through holes and connecting rods are provided.

[0065] Reference numerals

[0066] 1. Second diaphragm 2. Third sacrificial layer anchor area 3. Back plate 4. Second sacrificial layer anchor area

[0067] 5. First diaphragm 6. First sacrificial layer anchor area 7. Lower structure layer 8. First cavity

[0068] 9. Second cavity 10. Gas flow channel 11. Cavity sealing structure 12. Release hole

[0069] 13, through hole 14, connecting rod 15, third cavity 16, release stop structure

[0070] 3-1. Conductive layer 3-2. Structural layer DETAILED DESCRIPTION

[0071] The technical solution provided by the present invention is further illustrated below with reference to embodiments.

[0072] The present invention provides a dual-diaphragm silicon microphone and a manufacturing method thereof.

[0073] like Figure 1 The figure shows the structure of the dual-diaphragm silicon microphone of the present invention, which specifically includes:

[0074] (1) A gas flow channel 10 is provided in the lower structural layer 7;

[0075] (2) A first sacrificial layer is provided between the lower structural layer 7 and the first diaphragm 5. The first sacrificial layer is partially etched away to form a first cavity 8 and a first sacrificial layer anchoring area 6. The first cavity 8 provides a movement space for the first diaphragm 5. The first sacrificial layer anchoring area 6 connects the lower structural layer 7 and the first diaphragm 5.

[0076] (3) The first diaphragm 5 is provided on the first sacrificial layer;

[0077] (4) A second sacrificial layer is provided between the first diaphragm 5 and the back plate 3. The second sacrificial layer is partially etched away to form a second cavity 9 and a second sacrificial layer anchor area 4. The second cavity 9 provides a movement space for the first diaphragm 5. The second sacrificial layer anchor area 4 connects the first diaphragm 5 and the back plate 3.

[0078] (5) The back plate 3 is provided on the second sacrificial layer, and a through hole 13 is provided in the back plate 3;

[0079] (6) A third sacrificial layer is provided between the back plate 3 and the second diaphragm 1. The third sacrificial layer is partially etched and removed to form a third cavity 15 and a third sacrificial layer anchoring area 2. The third cavity 15 provides a movement space for the second diaphragm 1. The third cavity 15 and the second cavity 9 are connected by a through hole 13. The third sacrificial layer anchoring area 2 connects the back plate 3 and the second diaphragm 1.

[0080] (7) The second diaphragm 1 is provided on the third sacrificial layer;

[0081] (8) One or more connecting rods 14 are provided between the first diaphragm 5 and the second diaphragm 1. The connecting rods 14 pass through the through holes 13 in the back plate 3 to achieve synchronous movement of the first diaphragm 5 and the second diaphragm 1 after being subjected to external force.

[0082] (9) The second cavity 9 and the third cavity 15 are connected through the through hole 13 on the back plate 3 and are low-pressure cavities. The cavity pressure is lower than the external atmospheric pressure.

[0083] Preferably, the air pressure in the second cavity 9 and the third cavity 15 is much lower than the external atmospheric pressure, close to vacuum;

[0084] Preferably, the air pressure in the second cavity 9 and the third cavity 13 is kept constant, and the pressure variation within half a year is less than ±0.1 atmosphere;

[0085] Preferably, the back plate 3 is made of two composite layers, the lower layer of the two composite layers is the back plate lower structure layer 3-2, the upper layer of the two composite layers is the back plate conductive layer 3-1, and the back plate lower structure layer 3-2 is made of insulating material, such as Figure 2As shown, the back plate conductive layer 3-1 can be made of, for example, polysilicon or amorphous silicon, and the back plate lower structure layer 3-2 can be made of, for example, silicon nitride.

[0086] Preferably, the back plate 3 is made of two composite layers, the lower layer of the two composite layers is the back plate conductive layer 3-1, the upper layer of the two composite layers is the back plate structural layer 3-2, and the back plate structural layer 3-2 is made of insulating material, such as Figure 3 As shown, the back plate conductive layer 3-1 can be made of, for example, polysilicon or amorphous silicon, and the back plate structural layer 3-2 can be made of, for example, silicon nitride.

[0087] Preferably, the back plate 3 is made of three composite layers, the lower layer of the three composite layers is the back plate lower structure layer 3-2, the middle layer of the three composite layers is the back plate conductive layer 3-1, the upper layer of the three composite layers is the back plate structure layer 3-2, and both the back plate lower structure layer 3-2 and the back plate structure layer 3-2 are made of insulating materials, such as Figure 4 As shown, the back plate conductive layer 3-1 can be made of, for example, polysilicon or amorphous silicon, and the back plate upper structural layer 3-2 and the lower structural layer 3-2 can be made of, for example, silicon nitride.

[0088] Preferably, the back plate 3 is made of a three-layer composite layer, the lower layer of the three-layer composite layer is the back plate lower structural layer 3-2, the middle layer of the three-layer composite layer is the back plate conductive layer 3-1, the upper layer of the three-layer composite layer is the back plate upper structural layer 3-2, the side wall of the back plate conductive layer 3-1 is covered by the back plate upper structural layer 3-2, and the back plate lower structural layer 3-2 and the back plate upper structural layer 3-2 are both made of insulating materials, such as Figure 5 As shown, the back plate conductive layer 3-1 can be made of, for example, polysilicon or amorphous silicon, and the back plate upper structural layer 3-2 and the lower structural layer 3-2 can be made of, for example, silicon nitride.

[0089] Preferably, the connecting rod 14 between the first diaphragm 5 and the second diaphragm 1 is electrically insulated;

[0090] Preferably, the connecting rod 14 between the first diaphragm 5 and the second diaphragm 1 is formed by stacking multiple layers of materials. A typical connecting rod structure is as follows: Figure 6 (matching Figure 2 As shown in the back plate 3 structure shown in the figure, its connecting rod structure is specifically as follows: from bottom to top, it includes the second sacrificial layer part material, the back plate lower structure layer 3-2 part material, the back plate conductive layer 3-1 part material, the third sacrificial layer part material, and the second diaphragm 1 part material, wherein the back plate lower structure layer 3-2 material also wraps the side wall of the second sacrificial layer part material, and the second diaphragm 1 material also wraps the side wall of the third sacrificial layer part material;

[0091] like Figure 7 (matching Figure 3The connecting rod structure shown in the back plate 3 structure shown in the figure is specifically as follows: from bottom to top, it includes a portion of the second sacrificial layer material, a portion of the back plate conductive layer 3-1 material, a portion of the structural layer 3-2 material on the back plate, a portion of the third sacrificial layer material, and a portion of the second diaphragm 1 material, wherein the back plate conductive layer 3-1 material also wraps around the sidewalls of the second sacrificial layer material, and the second diaphragm 1 material also wraps around the sidewalls of the third sacrificial layer material;

[0092] like Figure 8 (matching Figure 4 The connecting rod structure shown in the back plate 3 structure shown in the figure is specifically as follows: from bottom to top, it includes, in sequence, the second sacrificial layer material, the back plate lower structural layer 3-2 material, the back plate conductive layer 3-1 material, the back plate structural layer 3-2 material, the third sacrificial layer material, and the second diaphragm 1 material, wherein the back plate lower structural layer 3-2 material also wraps the sidewalls of the second sacrificial layer material, and the second diaphragm 1 material also wraps the sidewalls of the third sacrificial layer material;

[0093] like Figure 9 (matching Figure 5 The connecting rod structure shown in the back plate 3 structure shown in the figure is specifically as follows: from bottom to top, it includes, in sequence, the second sacrificial layer portion material, the back plate lower structural layer 3-2 portion material, the back plate conductive layer 3-1 portion material, the back plate structural layer 3-2 portion material, the third sacrificial layer portion material, and the second diaphragm 1 portion material, wherein the back plate lower structural layer 3-2 material simultaneously wraps the side wall of the second sacrificial layer portion material, the back plate structural layer 3-2 material simultaneously wraps the side wall of the back plate conductive layer 3-1 portion material, and the second diaphragm 1 material simultaneously wraps the side wall of the third sacrificial layer portion material;

[0094] Preferably, a release stop structure 16 is provided on both sides of the boundary of the first sacrificial layer, the second sacrificial layer and the third sacrificial layer anchor area to accurately control the boundary of the sacrificial layer anchor area, such as Figure 11 As shown, the release stop structure 16 can be made of materials such as polysilicon, amorphous silicon, silicon nitride, etc.

[0095] Preferably, a release stop structure is provided on both sides of the anchor area boundary of the first sacrificial layer, the second sacrificial layer, and the third sacrificial layer and on the outside of the back plate 3 to precisely control the boundary between the anchor area of ​​the sacrificial layer and the back plate 3. Figure 12 As shown,

[0096] Preferably, a release stop structure 16 is provided on both sides of the anchor area boundary of the first sacrificial layer, the second sacrificial layer, and the third sacrificial layer, the outer side of the back plate 3, and the outer side of the first diaphragm 5, so as to accurately control the boundary of the sacrificial layer anchor area, the back plate 3, and the first diaphragm 5. Figure 13 As shown, the release stop structure 16 can be made of materials such as polysilicon, amorphous silicon, silicon nitride, etc.

[0097] Preferably, the second sacrificial layer and the third sacrificial layer are corroded and released through the release hole 12 provided in the second diaphragm 1 to form the second cavity 9 and the third cavity 15;

[0098] Preferably, a release hole sealing material is deposited on the second diaphragm 1 by CVD, and a cavity sealing structure 11 is patterned to achieve a pressure lower than the external environment in the second cavity 9 and the third cavity 15;

[0099] As a typical example, Figure 1 The key manufacturing process and sequence of the dual-diaphragm silicon microphone of the present invention are as follows: (wherein the lower structural layer is a silicon substrate)

[0100] (1) depositing a first sacrificial layer on the lower structural layer 7;

[0101] (2) depositing a first diaphragm 5 on the first sacrificial layer;

[0102] (3) depositing a second sacrificial layer on the first diaphragm 5;

[0103] (4) depositing a back electrode plate 3 on the second sacrificial layer and patterning to form one or more through holes 13;

[0104] (5) depositing a third sacrificial layer on the back plate 3 and patterning a deep groove for subsequent deposition of the film material of the connecting rod 14, the deep groove extending all the way to the surface of the first diaphragm 5; Figure 14 , which is a cross-sectional schematic diagram of the dual-diaphragm silicon microphone of the present invention provided with a plurality of through holes 13 and connecting rods 14 .

[0105] (6) depositing a connecting rod 14 film layer and patterning the connecting rod 14;

[0106] (7) depositing a second diaphragm 1 on the third sacrificial layer and patterning a release hole 12, completing the corrosion release of the second sacrificial layer and the third sacrificial layer through the release hole 12 to form a second cavity 9 and a third cavity 15;

[0107] (8) Using CVD method to deposit the release hole sealing material on the second diaphragm 1, and graphically forming the cavity sealing structure 11, to achieve a pressure lower than the external environment in the second cavity 9 and the third cavity 15; the number and position of the release holes 12 and the sealing structure 11 are not limited, such as Figure 10 , which is a cross-sectional schematic diagram of an embodiment of the dual-diaphragm silicon microphone of the present invention provided with two release holes 12 and a sealing structure 11.

[0108] (9) Photolithographic etching of the back side of the lower structural layer, with the etching stopping at the first sacrificial layer, to form a gas flow channel 10;

[0109] (10) Corrosion releases part of the material of the first sacrificial layer to form a first cavity 8, providing movement space for the first diaphragm 5.

[0110] As a typical example, Figure 6 The key manufacturing processes and sequences of the dual-diaphragm silicon microphone of the present invention are as follows:

[0111] (1) depositing a first sacrificial layer on the lower structural layer 7;

[0112] (2) depositing a first diaphragm 5 on the first sacrificial layer;

[0113] (3) depositing a second sacrificial layer on the first diaphragm 5 and patterning a portion of the connecting rod 14 and a groove surrounding the portion of the connecting rod 14 and extending through the surface of the first diaphragm;

[0114] (4) depositing a back electrode plate 3 on the second sacrificial layer, wherein the structural layer of the back electrode plate 3 fills the groove formed in step (3), and patterning the back electrode plate 3 to form one or more through holes 13, and patterning a portion of the connecting rod 14;

[0115] (5) depositing a third sacrificial layer on the back plate 3, and patterning to form a portion of the connecting rod 14 and a groove surrounding the portion of the connecting rod 14 and penetrating to the surface of the back plate conductive layer 3-1;

[0116] (6) depositing a second diaphragm 1 on the third sacrificial layer, the diaphragm filling the groove formed in step (5) to obtain the entire connecting rod 14, and patterning the second diaphragm 1 to form a release hole 12, completing the corrosion release of the second and third sacrificial layers through the release hole 12 to form a second cavity 9 and a third cavity 15;

[0117] (7) A sealing material for the release hole 12 is deposited on the second diaphragm 1 by CVD, and a cavity sealing structure 11 is formed by patterning, so as to achieve a pressure lower than the external environment in the second cavity 9 and the third cavity 15.

[0118] (8) Photolithographic etching of the back side of the lower structural layer 7, with the etching stopping at the first sacrificial layer, to form a gas flow channel 10;

[0119] (9) Corrosion releases part of the material of the first sacrificial layer to form a first cavity 8, providing movement space for the first diaphragm 5.

[0120] Preferably, the lower structural layer 7 is made of single crystal silicon material;

[0121] Preferably, the first sacrificial layer is made of silicon oxide, borosilicate glass, phosphosilicate glass, borophosphosilicate glass, or a composite material of at least two randomly stacked materials, and is deposited by thermal oxidation or CVD. Specifically, when the first sacrificial layer is silicon oxide, thermal oxidation or CVD deposition can be used, and when the first sacrificial layer is made of borosilicate glass, phosphosilicate glass, or borophosphosilicate glass, CVD deposition can be used. Preferably, the first diaphragm 5 and the second diaphragm 1 are made of polycrystalline silicon or amorphous silicon.

[0122] Preferably, the second sacrificial layer and the third sacrificial layer are made of silicon oxide, borosilicate glass, phosphosilicate glass, borophosphosilicate glass, or a composite material of at least two randomly stacked materials, and are deposited by CVD.

[0123] Preferably, the back plate 3 is made of polycrystalline silicon, amorphous silicon, a composite layer of polycrystalline silicon and silicon nitride, or a composite layer of amorphous silicon and silicon nitride;

[0124] Preferably, the upper and lower surfaces of the connecting rod 14 are electrically insulated;

[0125] Preferably, the connecting rod 14 is made of silicon nitride, a composite layer of silicon nitride and polysilicon, or a composite layer of silicon nitride and amorphous silicon;

[0126] Preferably, the first sacrificial layer, the second sacrificial layer, and the third sacrificial layer can be released by wet etching using HF solution, BOE solution, or vapor-phase hydrofluoric acid etching.

[0127] In an embodiment, the dual-diaphragm silicon microphone of the present invention is in a circular, square or polygonal shape.

[0128] From the above detailed description of the present invention, it can be seen that the manufacturing method of the dual-diaphragm silicon microphone of the present invention can accurately control the cavity boundary. The dual-diaphragm silicon microphone of the present invention has higher structural reliability and can effectively improve the signal-to-noise ratio.

[0129] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A dual-diaphragm silicon microphone, characterized in that: The microphone structure body comprises, from bottom to top, a lower structure layer (7), a first diaphragm (5), a back plate (3), and a second diaphragm (1); A first cavity (8) and a first sacrificial layer anchoring area (6) are provided between the lower structural layer (7) and the first diaphragm (5); a second cavity (9) and a second sacrificial layer anchoring area (4) are provided between the first diaphragm (5) and the back plate (3); the first cavity (8) and the second cavity (9) are used to provide a movement space for the first diaphragm (5); a third cavity (15) and a third sacrificial layer anchoring area (2) are provided between the back plate (3) and the second diaphragm (1); the third cavity (15) is used to provide a movement space for the second diaphragm (1); A through hole (13) is provided in the middle of the back plate (3), and the through hole (13) is used to connect the second cavity (9) and the third cavity (15); the back plate is configured as a multi-layer composite layer; A gas flow channel (10) is provided in the lower structural layer (7); A connecting rod (14) is provided between the first diaphragm (5) and the second diaphragm (1), and the connecting rod (14) passes through the through hole (13) to connect the first diaphragm (5) and the second diaphragm (1), so as to enable the first diaphragm (5) and the second diaphragm (1) to move synchronously; A release hole (12) is provided on the second diaphragm (1), and a cavity sealing structure (11) is provided on the release hole (12).

2. The dual-diaphragm silicon microphone according to claim 1, characterized in that: Release stop structures (16) are provided on the inner and outer sides of the first sacrificial layer anchor area (6), the second sacrificial layer anchor area (4), and the third sacrificial layer anchor area (2) for controlling the boundaries of the first sacrificial layer anchor area (6), the second sacrificial layer anchor area (4), and the third sacrificial layer anchor area (2).

3. The dual-diaphragm silicon microphone according to claim 2, characterized in that: The release stop structure (16) is also arranged on the outside of the back plate (3) and is used to control the boundary of the back plate (3).

4. The dual-diaphragm silicon microphone according to claim 3, characterized in that: The release stop structure (16) is also arranged on the outside of the first diaphragm (5) and is used to control the boundary of the first diaphragm (5).

5. The dual-diaphragm silicon microphone according to claim 1, characterized in that: The upper and lower surfaces of the connecting rod (14) are electrically insulated.

6. The dual-diaphragm silicon microphone according to claim 1, characterized in that: The materials of the first sacrificial layer anchor region (6), the second sacrificial layer anchor region (4), and the third sacrificial layer anchor region (2) are single materials of silicon oxide, borosilicate glass, phosphosilicate glass, or borosilicate glass, or composite materials of at least two of them stacked randomly; The material of the first diaphragm (5) and the second diaphragm (1) is polycrystalline silicon or amorphous silicon; The material of the lower structural layer (7) is silicon; The material of the connecting rod (14) is a single material of silicon nitride or a multi-layer composite material of silicon nitride and polysilicon and / or amorphous silicon stacked randomly.

7. A method for manufacturing the dual-diaphragm silicon microphone according to claim 1, comprising the following steps: 1) depositing a first sacrificial layer on the lower structural layer (7); 2) depositing a first diaphragm (5) on the first sacrificial layer; 3) depositing a second sacrificial layer on the first diaphragm (5); 4) depositing a back plate (3) on the second sacrificial layer and patterning to form one or more through holes (13); 5) depositing a third sacrificial layer on the back plate (3); 6) Graphically forming a deep groove for subsequent deposition of a film material for filling the connecting rod (14), the deep groove extending all the way to the surface of the first diaphragm (5), depositing the connecting rod (14) film layer, and graphically forming the connecting rod (14); or after the deposition is completed in steps 3), 4), and 5), respectively performing patterning, and then forming a partial structure of the connecting rod (14), and completing the process layer by layer to form the connecting rod (14); 7) depositing a second diaphragm (1) on the third sacrificial layer and patterning a release hole (12), completing the corrosion release of the second sacrificial layer and the third sacrificial layer through the release hole (12), forming a second sacrificial layer anchor area (4), a third sacrificial layer anchor area (2), a second cavity (9), and a third cavity (15); 8) depositing a sealing material for the release hole (12) on the second diaphragm (1), and patterning the material to form a cavity sealing structure (11); 9) Back-side photolithography etching of the lower structural layer (7), with the etching stopping at the first sacrificial layer, to form a gas flow channel (10); 10) Etching and releasing part of the material of the first sacrificial layer to form a first cavity (8) and a first sacrificial layer anchor region (6).

8. The method for manufacturing a dual-diaphragm silicon microphone according to claim 7, wherein: When the release stop structure (16) is provided on the inner and outer sides of the first sacrificial layer anchor area (6), the second sacrificial layer anchor area (4), and the third sacrificial layer anchor area (2), the specific steps are as follows: after the deposition of the first, second, and third sacrificial layers is completed in steps 1), 3), and 5), the sacrificial layers are patterned to form grooves, and then an anchor area release stop material is deposited to pattern the anchor area release stop structure (16); When a release stop structure (16) is provided on the inner and outer sides of the first sacrificial layer anchor area (6), the second sacrificial layer anchor area (4), the third sacrificial layer anchor area (2), and the outer side of the back plate (3), the specific steps are as follows: after the deposition of the first and second sacrificial layers, the back plate (3), and the third sacrificial layer is completed in steps 1), 3), 4), and 5), the back plate (3) and each sacrificial layer are patterned to form a groove, and then an anchor area release stop material is deposited to pattern the anchor area release stop structure (16); When a release stop structure (16) is provided on the inner and outer sides of the first sacrificial layer anchor area (6), the second sacrificial layer anchor area (4), and the third sacrificial layer anchor area (2), as well as on the outer sides of the first diaphragm (5) and the back plate (3), the specific steps are as follows: after the deposition of the first sacrificial layer, the first diaphragm (5), the second sacrificial layer, the back plate (3), and the third sacrificial layer is completed in steps 1), 2), 3), 4), and 5), the first diaphragm (5), the back plate (3), and each sacrificial layer are patterned to form a groove, and then an anchor area release stop material is deposited to pattern the anchor area release stop structure (16); The release stop structure (16) is made of polysilicon, amorphous silicon or silicon nitride.

9. The method for manufacturing a dual-diaphragm silicon microphone according to claim 7, wherein: The first sacrificial layer is deposited by thermal oxidation or chemical vapor deposition (CVD). The deposition method of the second sacrificial layer, the third sacrificial layer, the first diaphragm (5), the second diaphragm (1), and the back plate (3), and the method of depositing the release hole sealing material on the second diaphragm (1) are CVD; The CVD includes: low pressure chemical vapor deposition LPCVD, atmospheric pressure chemical vapor deposition APCVD, sub-atmospheric pressure chemical vapor deposition SACVD, plasma enhanced chemical vapor deposition PECVD; The etching release of the first sacrificial layer, the second sacrificial layer and the third sacrificial layer is achieved by wet etching with a hydrofluoric acid HF solution, a buffered oxide etchant BOE solution or vapor-phase hydrofluoric acid Vapor-phase HF etching.

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