MEMS microphone and manufacturing method thereof

Abstract

The invention provides an MEMS microphone and a manufacturing method thereof.The MEMS microphone comprises a substrate with a cavity, a vibrating diaphragm supported on the substrate and a back plate spaced from the vibrating diaphragm, the vibrating diaphragm comprises a fixing part fixedly connected with the substrate and a vibrating part suspended above the cavity, and the fixing part is fixedly connected with the substrate. The vibration part comprises a plane part, a plurality of concave diaphragm parts arranged on the plane part at intervals and a connecting part for connecting the plane part and the concave diaphragm parts, each concave diaphragm part comprises a first silicon nitride layer, a silicon oxide layer and a second silicon nitride layer which are sequentially stacked along the vibration direction of the diaphragm, and the first silicon nitride layer is closer to the substrate than the second silicon nitride layer. According to the MEMS microphone, the composite material is adopted to manufacture the vibrating diaphragm with the corrugated shape, the vibrating diaphragm can generate large displacement under sound pressure, so that high sensitivity is obtained, the corrugated vibrating diaphragm made of the composite material can decompose stress, the strength of the vibrating diaphragm is enhanced, and the reliability of the MEMS microphone is improved.

Description

Technical field

[0001] The present invention relates to the field of acoustic-to-electrical conversion, and in particular to a MEMS microphone and a manufacturing method thereof. [Background Technology]

[0002] With the development of wireless communications, users have higher and higher requirements for the call quality of mobile phones. The microphone is the voice pickup device of the mobile phone, and its design directly affects the call quality of the mobile phone.

[0003] Currently, the microphone that is most widely used in mobile phones is the MEMS microphone. In related technologies, the diaphragm of the microphone is completely fixed, that is, the upper and lower surfaces of the microphone diaphragm are covered and fixed to form a fixed part, which will result in lower sensitivity of the microphone. For this type of microphone, a diaphragm with a corrugated structure is generally used to overcome the problem of low sensitivity. However, the problem faced by the diaphragm with corrugations is that the steps of the corrugations will cause stress concentration, which will cause the diaphragm to be weak and easy to break.

[0004] Therefore, it is necessary to provide a new MEMS microphone to solve the above technical problems. [Summary of the invention]

[0005] The object of the present invention is to provide a MEMS microphone with high sensitivity and high structural strength.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A MEMS microphone comprising: a substrate having a cavity, a diaphragm supported on the substrate, and a backplate spaced apart from the diaphragm; the diaphragm comprising a fixed portion fixedly connected to the substrate and a vibrating portion suspended above the cavity; the vibrating portion comprising a planar portion, a plurality of recessed diaphragm portions spaced apart from the planar portion, and a connecting portion connecting the planar portion and the recessed diaphragm portions; the recessed diaphragm portion comprising a first silicon nitride layer, a silicon oxide layer, and a second silicon nitride layer stacked in sequence along a vibration direction of the diaphragm; the first silicon nitride layer being closer to the substrate than the second silicon nitride layer.

[0007] Preferably, the fixing portion and the planar portion both include a first silicon nitride layer, a polysilicon layer, and a second silicon nitride layer stacked in sequence along the vibration direction of the diaphragm, and the first silicon nitride layer is closer to the substrate than the second silicon nitride layer.

[0008] Preferably, the connecting portion includes a first silicon nitride layer, a polysilicon layer, a silicon oxide layer and a second silicon nitride layer stacked in sequence along the vibration direction of the diaphragm, and the first silicon nitride layer is closer to the substrate than the second silicon nitride layer.

[0009] Preferably, the thickness of the connecting portion of the diaphragm is greater than the thickness of the fixing portion of the diaphragm, the thickness of the planar portion, and the thickness of the recessed diaphragm portion.

[0010] Preferably, the thickness of the connecting portion of the diaphragm is H1, the thickness of the planar portion of the diaphragm is H2, and 2.6≤H1 / H2≤3.2.

[0011] Preferably, the recessed depth of the recessed diaphragm portion is greater than the sum of the thickness of the first silicon nitride layer and the thickness of the polysilicon layer.

[0012] Preferably, the thickness of the silicon oxide layer is greater than or equal to the thickness of the polysilicon layer.

[0013] Preferably, the diaphragm includes a first surface facing the substrate and a second surface opposite to the first surface, the back plate is arranged on a side of the diaphragm away from the substrate, and the MEMS microphone also includes a spacer layer arranged between the diaphragm and the back plate, and part of the back plate and part of the spacer layer are laminated on the second surface of the diaphragm.

[0014] Compared to related technologies, the present invention provides a MEMS microphone comprising: a substrate having a cavity, a diaphragm supported on the substrate, and a backplate spaced apart from the diaphragm. The diaphragm comprises a fixed portion fixedly connected to the substrate and a vibrating portion suspended above the cavity. The vibrating portion comprises a planar portion, a plurality of recessed diaphragm portions spaced apart from the planar portion, and a connecting portion connecting the planar portion and the recessed diaphragm portions. The recessed diaphragm portion comprises a first silicon nitride layer, a silicon oxide layer, and a second silicon nitride layer stacked in sequence along the diaphragm's vibration direction. The first silicon nitride layer is closer to the substrate than the second silicon nitride layer. The diaphragm of the MEMS microphone of the present invention is made of a composite material. The diaphragm can produce a large displacement under sound pressure, thereby improving the diaphragm's mechanical sensitivity. Furthermore, the composite material can reduce the diaphragm's stress and increase its strength, enabling it to achieve a high pass rate in reliability tests.

[0015] Another object of the present invention is to provide a method for manufacturing a MEMS microphone, wherein the microphone manufactured by the method has not only high sensitivity but also high structural strength.

[0016] In order to achieve the above object, the technical solution of the present invention is as follows: a method for manufacturing a MEMS microphone, the method for manufacturing a MEMS microphone comprising the following steps:

[0017] providing a substrate layer;

[0018] depositing a silicon dioxide layer on the substrate layer, and etching the silicon dioxide layer to form a gap;

[0019] Depositing a first silicon nitride layer on the substrate layer and the silicon dioxide layer, wherein the first silicon nitride layer includes a first recessed portion located in the gap;

[0020] depositing a polysilicon layer on the first silicon nitride layer, and removing a portion of the polysilicon layer located in the first recess;

[0021] Depositing a silicon oxide layer on the polysilicon layer and the first silicon nitride layer, etching the silicon oxide layer, leaving the remaining silicon oxide layer located in the first recess and extending onto a portion of the polysilicon layer connected to the first recess, and forming a second recess in the first recess.

[0022] depositing a second silicon nitride layer on the silicon oxide layer and the polysilicon layer;

[0023] forming a spacer layer and a back plate on the substrate layer;

[0024] The substrate layer is reversely etched to form a substrate with a cavity, and the silicon dioxide layer is removed to release the silicon dioxide layer to form a diaphragm.

[0025] Preferably, the diaphragm includes a fixed part fixedly connected to the substrate and a vibrating part suspended above the cavity, the vibrating part includes a planar part, a plurality of recessed diaphragm parts spaced apart from the planar part, and a connecting part connecting the planar part and the recessed diaphragm part, the recessed diaphragm part includes a first silicon nitride layer, a silicon oxide layer, and a second silicon nitride layer stacked in sequence along the vibration direction of the diaphragm.

[0026] Compared with the related art, the present invention provides a method for manufacturing a MEMS microphone. The diaphragm of the microphone manufactured by this manufacturing method is made of a composite material. The diaphragm can produce a large displacement under sound pressure, thereby improving the mechanical sensitivity of the diaphragm. At the same time, the diaphragm made of the composite material can reduce the stress of the diaphragm and increase the strength of the diaphragm, so that it can obtain a higher pass rate in reliability experiments.

Brief Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art in the art can also derive other drawings based on these drawings without inventive efforts. Among them:

[0028] Figure 1 A schematic diagram of a three-dimensional structure of a partial structure of a MEMS microphone of the present invention;

[0029] Figures 2 to 8For example Figure 1 The manufacturing flow chart of MEMS microphone is shown. [Specific implementation method]

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] See also Figure 1 and Figure 8 As shown, the present invention provides a MEMS microphone 100, Figure 1 The schematic diagram of the three-dimensional structure of the partial structure of the MEMS microphone 100 of the present invention is only a quarter of the structure of the entire MEMS microphone 100. The entire MEMS microphone 100 is composed of four Figure 1 The MEMS microphone 100 includes a substrate 1 having a cavity 10 , a diaphragm 2 supported on the substrate 1 , a back plate 3 spaced apart from the diaphragm 2 , and a spacer layer 4 disposed between the diaphragm 2 and the back plate 3 .

[0032] The diaphragm 2 includes a fixed portion 21 fixedly connected to the substrate 1 and a vibrating portion 22 suspended above the cavity 10. The vibrating portion 22 includes a planar portion 23, a plurality of recessed diaphragm portions 24 spaced apart from the planar portion 23, and a connecting portion 25 connecting the planar portion 23 and the recessed diaphragm portions 24. The recessed diaphragm portion 24 includes a first silicon nitride layer 261, a silicon oxide layer 262, and a second silicon nitride layer 263 stacked in sequence along the vibration direction of the diaphragm 2. The fixed portion 21 and the planar portion 23 each include a first silicon nitride layer 261, a polysilicon layer 264, and a second silicon nitride layer 263 stacked in sequence along the vibration direction of the diaphragm 2. The connecting portion 25 includes a first silicon nitride layer 261, a polysilicon layer 264, a silicon oxide layer 262, and a second silicon nitride layer 263 stacked in sequence along the vibration direction of the diaphragm 2. The first silicon nitride layer 261 of the recessed diaphragm portion 24 is the same layer as the first silicon nitride layer 261 of the fixed portion 21, the planar portion 23, and the connecting portion 25. The second silicon nitride layer 263 of the recessed diaphragm portion 24 is the same layer as the second silicon nitride layer 263 of the fixed portion 21, the planar portion 23, and the connecting portion 25. The first silicon nitride layer 261 of the recessed diaphragm portion 24, the fixed portion 21, the planar portion 23, and the connecting portion 25 is closer to the substrate 1 than the second silicon nitride layer 263.

[0033] The thickness of the connecting portion 25 of the diaphragm 2 is the area with the largest thickness of the entire diaphragm 2, that is, the thickness of the connecting portion 25 is greater than the thickness of the fixing portion 21 of the diaphragm 2, the thickness of the planar portion 23, and the thickness of the recessed diaphragm portion 24. Optionally, the thickness of the connecting portion 25 of the diaphragm 2 is H1, and the thickness of the planar portion 23 of the diaphragm 2 is H2, then 2.6≤H1 / H2≤3.2 is satisfied. The recessed depth of the recessed diaphragm portion 24 is greater than the sum of the thickness of the first silicon nitride layer 261 and the thickness of the polysilicon layer 264, as shown in FIG. Figure 8 As shown, the recessed diaphragm portion 24 has a recessed depth D. The thickness of the silicon oxide layer 262 is greater than or equal to the thickness of the polysilicon layer 264. The recessed diaphragm portion 24, the planar portion 23, and the connecting portion 25 of the present invention together form a corrugated structure, which can improve the mechanical sensitivity of the diaphragm.

[0034] In this embodiment, the diaphragm 2 is closer to the substrate 1 than the backplate 3. That is, the backplate 3 is disposed on the side of the diaphragm 2 away from the substrate 1. The diaphragm 2 includes a first surface 201 facing the substrate 1 and a second surface 202 opposite the first surface 201. The first surface 201 is located on the first silicon nitride layer 261, and the second surface 202 is located on the second silicon nitride layer 263. Part of the backplate 3 and part of the spacer layer 4 are pressed against the second surface 202 of the diaphragm 2. In other embodiments, the backplate 3 may be closer to the substrate 1 than the diaphragm 2.

[0035] The back plate 3 includes a back plate support layer 31 and an electrode layer 32 provided on a side of the back plate support layer 31 close to the diaphragm 2 . The back plate support layer 31 is made of silicon nitride material, and the electrode layer 32 is made of polysilicon material.

[0036] The spacer layer 4 is made of silicon oxide.

[0037] Compared to related technologies, the present invention provides a MEMS microphone comprising: a substrate having a cavity, a diaphragm supported on the substrate, and a backplate spaced apart from the diaphragm. The diaphragm comprises a fixed portion fixedly connected to the substrate and a vibrating portion suspended above the cavity. The vibrating portion comprises a planar portion, a plurality of recessed diaphragm portions spaced apart from the planar portion, and a connecting portion connecting the planar portion and the recessed diaphragm portions. The recessed diaphragm portion comprises a first silicon nitride layer, a silicon oxide layer, and a second silicon nitride layer stacked in sequence along the diaphragm's vibration direction. The first silicon nitride layer is closer to the substrate than the second silicon nitride layer. The diaphragm of the MEMS microphone of the present invention is made of a composite material. The diaphragm can produce a large displacement under sound pressure, thereby improving the diaphragm's mechanical sensitivity. Furthermore, the composite material can reduce the diaphragm's stress and increase its strength, enabling it to achieve a high pass rate in reliability tests.

[0038] See also Figures 2 to 8 The present invention further provides a method for manufacturing a MEMS microphone 100, the method comprising the following steps:

[0039] A substrate material is provided to form the substrate layer 11 .

[0040] A silicon dioxide layer 5 is deposited on the substrate layer 11 , and the silicon dioxide layer 5 is etched to form a gap 51 .

[0041] A first silicon nitride layer 261 is deposited on the substrate layer 11 and the silicon dioxide layer 5 . The first silicon nitride layer 261 includes a first recessed portion 241 located in the gap 51 .

[0042] A polysilicon layer 264 is deposited on the first silicon nitride layer 261 , and a portion of the polysilicon layer 264 located in the first recess 241 is removed to expose a portion of the first silicon nitride layer 261 .

[0043] A silicon oxide layer 262 is deposited on the polysilicon layer 264 and the first silicon nitride layer 261, and the silicon oxide layer 262 is etched so that the remaining silicon oxide layer 262 is located in the first recess 241 and extends to the portion of the polysilicon layer 264 connected to the first recess 241. The silicon oxide layer 262 is located in the first recess 241 to form a second recess 242.

[0044] A second silicon nitride layer 263 is deposited on the silicon oxide layer 262 and the polysilicon layer 264 .

[0045] A spacer layer 4 and a back plate 3 are formed on the substrate layer 11 .

[0046] The substrate layer 11 is reversely etched to form a substrate 1 having a cavity 10 , and the silicon dioxide layer 5 is removed to release and form a diaphragm 2 .

[0047] At this point, the entire MEMS microphone is completed.

[0048] Compared with the related art, the present invention provides a method for manufacturing a MEMS microphone. The diaphragm of the microphone manufactured by this manufacturing method is made of a composite material. The diaphragm can produce a large displacement under sound pressure, thereby improving the mechanical sensitivity of the diaphragm. At the same time, the diaphragm made of the composite material can reduce the stress of the diaphragm and increase the strength of the diaphragm, so that it can obtain a higher pass rate in reliability experiments.

[0049] The above description is only an embodiment of the present invention. It should be pointed out that those skilled in the art can make improvements without departing from the creative concept of the present invention, but these improvements all fall within the scope of protection of the present invention.

Claims

1. A MEMS microphone, comprising: A substrate having a cavity, a diaphragm supported on the substrate, and a back plate spaced apart from the diaphragm, characterized in that the diaphragm includes a fixed portion fixedly connected to the substrate and a vibrating portion suspended above the cavity, the vibrating portion includes a planar portion, a plurality of recessed diaphragm portions spaced apart from the planar portion, and a connecting portion connecting the planar portion and the recessed diaphragm portion, the recessed diaphragm portion includes a first silicon nitride layer, a silicon oxide layer, and a second silicon nitride layer stacked in sequence along the vibration direction of the diaphragm, the first silicon nitride layer being closer to the substrate than the second silicon nitride layer.

2. The MEMS microphone according to claim 1, wherein: The fixing portion and the planar portion both include a first silicon nitride layer, a polysilicon layer, and a second silicon nitride layer stacked in sequence along the vibration direction of the diaphragm. The first silicon nitride layer is closer to the substrate than the second silicon nitride layer.

3. The MEMS microphone according to claim 1, wherein: The connecting portion includes a first silicon nitride layer, a polysilicon layer, a silicon oxide layer, and a second silicon nitride layer stacked in sequence along a vibration direction of the diaphragm. The first silicon nitride layer is closer to the substrate than the second silicon nitride layer.

4. The MEMS microphone according to claim 1, wherein: The thickness of the connecting portion of the diaphragm is greater than the thickness of the fixing portion of the diaphragm, the thickness of the planar portion, and the thickness of the concave diaphragm portion.

5. The MEMS microphone according to claim 4, characterized in that The thickness of the connecting portion of the diaphragm is H1, the thickness of the planar portion of the diaphragm is H2, and 2.6≤H1 / H2≤3.

2.

6. The MEMS microphone according to claim 2, wherein: The recessed diaphragm portion has a recessed depth greater than the sum of the thickness of the first silicon nitride layer and the thickness of the polysilicon layer.

7. The MEMS microphone according to claim 2, wherein: The thickness of the silicon oxide layer is greater than or equal to the thickness of the polysilicon layer.

8. The MEMS microphone according to claim 1, wherein: The diaphragm includes a first surface facing the substrate and a second surface opposite to the first surface. The backplate is arranged on a side of the diaphragm away from the substrate. The MEMS microphone also includes a spacer layer arranged between the diaphragm and the backplate. Part of the backplate and part of the spacer layer are laminated on the second surface of the diaphragm.

9. A method for manufacturing a MEMS microphone, characterized in that: The manufacturing method of the MEMS microphone comprises the following steps: providing a substrate layer; depositing a silicon dioxide layer on the substrate layer, and etching the silicon dioxide layer to form a gap; Depositing a first silicon nitride layer on the substrate layer and the silicon dioxide layer, wherein the first silicon nitride layer includes a first recessed portion located in the gap; depositing a polysilicon layer on the first silicon nitride layer, and removing a portion of the polysilicon layer located in the first recess; Depositing a silicon oxide layer on the polysilicon layer and the first silicon nitride layer, etching the silicon oxide layer, leaving the remaining silicon oxide layer located in the first recess and extending onto a portion of the polysilicon layer connected to the first recess, and forming a second recess in the first recess. depositing a second silicon nitride layer on the silicon oxide layer and the polysilicon layer; forming a spacer layer and a back plate on the substrate layer; The substrate layer is reversely etched to form a substrate with a cavity, and the silicon dioxide layer is removed to release the silicon dioxide layer to form a diaphragm.

10. The method for manufacturing a MEMS microphone according to claim 9, wherein: The diaphragm includes a fixed part fixedly connected to the substrate and a vibrating part suspended above the cavity, the vibrating part includes a planar part, a plurality of recessed diaphragm parts spaced apart from the planar part, and a connecting part connecting the planar part and the recessed diaphragm part, the recessed diaphragm part includes a first silicon nitride layer, a silicon oxide layer, and a second silicon nitride layer stacked in sequence along the vibration direction of the diaphragm.

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