CN-122027959-A - MEMS acoustic sensor and preparation method thereof

CN122027959ACN 122027959 ACN122027959 ACN 122027959ACN-122027959-A

Abstract

The invention provides an MEMS acoustic sensor and a preparation method thereof, wherein the substrate comprises a first area and a second area, the first area surrounds the second area, a supporting structure is positioned on part of the first area, a silicon vibrating diaphragm is positioned on the substrate, each of a plurality of piezoresistors is positioned in the silicon vibrating diaphragm, the piezoresistors form a bridge structure, a back electrode plate is positioned on part of the supporting structure and the silicon vibrating diaphragm, a piezoresistor electrode is positioned on the surface of each piezoresistor, a silicon vibrating diaphragm electrode is positioned on the surface of an edge area of the silicon vibrating diaphragm, and a back electrode plate electrode is positioned on the surface of the back electrode plate on part of the first area. Therefore, the sensor can monitor the dynamic stress of the silicon diaphragm through the bridge structure integrated on the silicon diaphragm, regulate and control the working state of the silicon diaphragm based on the monitored dynamic stress of the silicon diaphragm, avoid the silicon diaphragm from being broken due to overlarge stress and give consideration to higher sensitivity.

Inventors

Shan Yameng
ZHANG JIANQIANG
HUANG JINHAI
LIU YONGBO

Assignees

广州增芯科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260211

Claims (10)

1. A kind of acoustic sensor of the MEMS, characterized by comprising the following steps: a substrate comprising a first region and a second region, the first region surrounding the second region; A support structure located on a portion of the substrate in the first region, the support structure having a lateral recess with a slot opening toward and surrounding the second region; the silicon vibrating diaphragm is positioned on the substrate, the edge area of the silicon vibrating diaphragm is filled with the transverse groove, and the silicon vibrating diaphragm is supported by the supporting structure and is spaced from the substrate; The piezoresistors are positioned in the silicon diaphragm and are adjacent to the edge area of the silicon diaphragm, the projection of each piezoresistor to the substrate spans the boundary between the first area and the second area, and the piezoresistors form a bridge structure; The back electrode plate is positioned on part of the supporting structure and the silicon vibrating diaphragm, a spacing cavity is arranged between the back electrode plate and the silicon vibrating diaphragm, the back electrode plate on the second area is provided with a plurality of through back electrode plate through holes, and the back electrode plate through holes are communicated with the spacing cavity; the piezoresistor electrode penetrates through the back electrode plate on the surface of the piezoresistor and is contacted with the surface of each piezoresistor; the silicon vibrating diaphragm electrode penetrates through the supporting structure on the transverse groove and is contacted with the surface of the edge area of the silicon vibrating diaphragm; and a back electrode plate electrode positioned on the surface of the back electrode plate on part of the first area.
2. The MEMS acoustic sensor of claim 1, wherein a spaced region between the silicon diaphragm and the substrate forms a diaphragm cavity; The MEMS acoustic sensor further comprises: And the substrate cavity is positioned in the second region of the substrate, penetrates through the substrate and is communicated with the vibrating diaphragm cavity.
3. The MEMS acoustic sensor of claim 1, further comprising a backplate protective layer on a surface of the backplate, each backplate through hole further passing through the backplate protective layer.
4. The MEMS acoustic sensor of claim 1, wherein the support structure comprises a first support layer and a second support layer on the first support layer; The first support layer is positioned on the surface of the substrate in part of the first region; the second supporting layer comprises a first part and a second part which are connected, the thickness of the first part is larger than that of the second part, the bottom surface of the first part is contacted with the surface of part of the first supporting layer, and the bottom surface of the second part, the side wall of the first part and the surface of the first supporting layer which is not contacted form a transverse groove.
5. The MEMS acoustic sensor according to claim 1, wherein each of the piezoresistors includes a lightly doped region and heavily doped regions located on opposite sides of the lightly doped region.
6. A method of manufacturing a MEMS acoustic sensor, the method comprising: Providing a substrate, wherein the substrate comprises a first region and a second region, and the first region surrounds the second region; Forming a support structure and a silicon vibrating diaphragm on the substrate, wherein the support structure is formed on part of the substrate in the first area, the support structure is provided with a transverse groove with a notch facing the second area and surrounding the second area, the silicon vibrating diaphragm is positioned on the substrate in the second area, the edge area of the silicon vibrating diaphragm extends and fills the transverse groove, and the silicon vibrating diaphragm is supported by the support structure and is spaced from the substrate to form a vibrating diaphragm cavity; Forming a plurality of piezoresistors adjacent to the edge area of the silicon diaphragm in the silicon diaphragm, wherein the projection of each piezoresistor to the substrate spans the boundary between the first area and the second area, and the piezoresistors form a bridge structure; Forming a back electrode plate on part of the supporting structure and the silicon vibrating diaphragm, wherein a spacing cavity is formed between the back electrode plate and the silicon vibrating diaphragm, the back electrode plate on the second area is provided with a plurality of back electrode plate through holes penetrating through the back electrode plate, and the back electrode plate through holes are communicated with the spacing cavity; Forming a piezoresistor electrode penetrating through the back electrode plate on the surface of each piezoresistor; forming a silicon diaphragm electrode penetrating through the support structure on the transverse groove on the surface of the edge area of the silicon diaphragm; And forming a back electrode plate electrode on the surface of the back electrode plate on part of the first area.
7. The method of manufacturing a MEMS acoustic sensor according to claim 6 wherein after forming the backplate electrode, the method further comprises forming a substrate cavity through the substrate in the second region, the substrate cavity communicating with the diaphragm cavity.
8. The method of manufacturing a MEMS acoustic sensor according to claim 6, wherein forming a backplate over a portion of the support structure and the silicon diaphragm comprises: forming an initial back electrode plate on a part of the surface of the supporting structure and the silicon diaphragm; forming the initial back electrode plate protective layer on the surface of the initial back electrode plate; Before forming the substrate cavity and after forming the piezoresistor electrode, the silicon diaphragm electrode and the back electrode plate electrode, forming the back electrode plate on part of the supporting structure and the silicon diaphragm further comprises etching the initial back electrode plate protection layer and the initial back electrode plate to form a plurality of back electrode plate through holes penetrating through the initial back electrode plate and the initial back electrode plate protection layer to form a back electrode plate and a back electrode plate protection layer.
9. The method of manufacturing a MEMS acoustic sensor according to claim 8, wherein after forming the back plate electrode and before forming the back plate via hole, the method further comprises forming an initial protection layer on the surface of the varistor electrode, the surface of the silicon diaphragm electrode, the surface of the back plate electrode, and the surface of the initial back plate protection layer; in the process of forming the back plate through hole, the initial protection layer is also etched, so that the back plate through hole also penetrates through the initial protection layer to form a protection layer; after forming the diaphragm cavity, the method further includes removing the protective layer.
10. The method of manufacturing a MEMS acoustic sensor according to claim 9, wherein the method of forming a support structure on a portion of the substrate in the first region comprises: Forming an initial first support layer on the surface of the substrate before forming the silicon diaphragm; after the piezoresistor is formed and before the back electrode plate is formed, an initial second supporting layer is formed on the surface of the initial first supporting layer and the surface of the silicon vibrating diaphragm; Removing the initial first support layer on the second region and on a portion of the first region to form a first support layer before removing the protective layer and after forming the substrate cavity; after forming the first support layer and before removing the protective layer, removing the initial second support layer on the second region and part of the initial second support layer on the first region to form a second support layer, wherein the second support layer comprises a first part and a second part which are connected, the thickness of the first part is larger than that of the second part, the bottom surface of the first part is contacted with part of the surface of the first support layer, and the bottom surface of the second part, the side wall of the first part and the surface of the first support layer which is not contacted form a transverse groove.

Description

MEMS acoustic sensor and preparation method thereof Technical Field The invention relates to the technical field of semiconductors, in particular to an MEMS acoustic sensor and a preparation method thereof. Background In the MEMS acoustic sensor, a vibrating diaphragm is a core sensitive element, and the vibrating diaphragm generates mechanical vibration by receiving the acoustic wave signals and converts the mechanical vibration into an electric signal to realize acoustic detection. However, in a high sound pressure environment or an abnormal condition, the diaphragm is easily broken due to the fact that the stress generated by the high sound pressure exceeds the limit that the diaphragm material can withstand, and the MEMS acoustic sensor fails. Disclosure of Invention The invention provides an MEMS acoustic sensor and a preparation method thereof, which can monitor the dynamic stress of a silicon diaphragm, so that the working state of the silicon diaphragm can be adjusted according to the stress change of the silicon diaphragm, and the silicon diaphragm is prevented from being broken due to overlarge stress. According to a first aspect of the present invention there is provided a MEMS acoustic sensor comprising: a substrate comprising a first region and a second region, the first region surrounding the second region; A support structure located on a portion of the substrate in the first region, the support structure having a lateral recess with a slot opening toward and surrounding the second region; the silicon vibrating diaphragm is positioned on the substrate, the edge area of the silicon vibrating diaphragm is filled with the transverse groove, and the silicon vibrating diaphragm is supported by the supporting structure and is spaced from the substrate; The piezoresistors are positioned in the silicon diaphragm and are adjacent to the edge area of the silicon diaphragm, the projection of each piezoresistor to the substrate spans the boundary between the first area and the second area, and the piezoresistors form a bridge structure; The back electrode plate is positioned on part of the supporting structure and the silicon vibrating diaphragm, a spacing cavity is arranged between the back electrode plate and the silicon vibrating diaphragm, the back electrode plate on the second area is provided with a plurality of through back electrode plate through holes, and the back electrode plate through holes are communicated with the spacing cavity; the piezoresistor electrode penetrates through the back electrode plate on the surface of the piezoresistor and is contacted with the surface of each piezoresistor; the silicon vibrating diaphragm electrode penetrates through the supporting structure on the transverse groove and is contacted with the surface of the edge area of the silicon vibrating diaphragm; and a back electrode plate electrode positioned on the surface of the back electrode plate on part of the first area. Optionally, a diaphragm cavity is formed by a spacing region between the silicon diaphragm and the substrate; The MEMS acoustic sensor further comprises: And the substrate cavity is positioned in the second region of the substrate, penetrates through the substrate and is communicated with the vibrating diaphragm cavity. Optionally, the back electrode plate protective layer is positioned on the surface of the back electrode plate, and each back electrode plate through hole also penetrates through the back electrode plate protective layer. Optionally, the support structure comprises a first support layer and a second support layer positioned on the first support layer; The first support layer is positioned on the surface of the substrate in part of the first region; the second supporting layer comprises a first part and a second part which are connected, the thickness of the first part is larger than that of the second part, the bottom surface of the first part is contacted with the surface of part of the first supporting layer, and the bottom surface of the second part, the side wall of the first part and the surface of the first supporting layer which is not contacted form a transverse groove. Optionally, each varistor includes a lightly doped region and heavily doped regions located on two sides of the lightly doped region. According to a second aspect of the present invention, there is provided a method of manufacturing a MEMS acoustic sensor for manufacturing a MEMS acoustic sensor as described above, the method comprising: Providing a substrate, wherein the substrate comprises a first region and a second region, and the first region surrounds the second region; forming a support structure and a silicon vibrating diaphragm on the substrate, wherein the support structure is formed on part of the substrate in the first area, the support structure is provided with a transverse groove with a notch facing the second area and surrounding the second area, the silicon vibrating diaphragm is positi