CN113873413A

CN113873413A - Capacitive sensor and microphone

Info

Publication number: CN113873413A
Application number: CN202111161567.3A
Authority: CN
Inventors: 石正雨; 王琳琳; 张睿
Original assignee: AAC Acoustic Technologies Shenzhen Co Ltd
Current assignee: AAC Technologies Holdings Shenzhen Co Ltd
Priority date: 2021-09-30
Filing date: 2021-09-30
Publication date: 2021-12-31

Abstract

The invention provides a capacitance type sensor and a microphone, wherein the capacitance type sensor comprises a substrate with a back cavity and a capacitance system arranged on the substrate, the capacitance system comprises a back plate and a vibrating diaphragm which are arranged at intervals, and a cavity is formed between the back plate and the vibrating diaphragm; the first surface of the back plate facing the vibrating diaphragm is provided with an elastic supporting structure, and the elastic supporting structure is arranged in the central area of the back plate. According to the invention, the rigidity of the middle part of the vibrating diaphragm is close to that of the periphery of the vibrating diaphragm through the elastic support of the middle part of the vibrating diaphragm, and the pressure acts on the vibrating diaphragm when the sensor works, so that the deformation of each part of the vibrating diaphragm is more uniform, and thus, the chip has a larger effective area, a higher pull-in voltage and a higher SNR (signal to noise ratio) performance.

Description

Capacitive sensor and microphone

[ technical field ] A method for producing a semiconductor device

The invention relates to a capacitive sensor and application thereof, in particular to a capacitive sensor with a back plate elastically supported and an acoustic device applying the sensor.

[ background of the invention ]

MEMS capacitive sensors are widely used in acoustic devices such as common MEMS capacitive microphone structures. As shown in fig. 1, the capacitive sensor has a back plate and a diaphragm, which are oppositely disposed, the back plate and the diaphragm are separated by a sacrificial layer, the periphery of the back plate is fixed, and the diaphragm is fixed in the peripheral area.

When the circumference of the diaphragm is partially or completely fixed, the pressure acts on the diaphragm when the sensor works, the peripheral movement displacement of the diaphragm is small, the central movement displacement of the diaphragm is large, the effective area of the chip is far smaller than the actual area of the chip, and the sensor has smaller pull-in voltage.

In view of these problems, it is necessary to provide a new capacitive sensor so that the deformation of the vibration region of the diaphragm is more uniform.

[ summary of the invention ]

In view of the above problems, the present invention provides a capacitive sensor and a microphone including the same.

Specifically, the scheme provided by the invention is as follows:

a capacitance type sensor comprises a substrate with a back cavity and a capacitance system arranged on the substrate, wherein the capacitance system comprises a back plate and a vibrating diaphragm which are oppositely arranged at intervals, and a cavity is formed between the back plate and the vibrating diaphragm; the first surface of the back plate facing the vibrating diaphragm is provided with an elastic supporting structure, and the elastic supporting structure is arranged in the central area of the back plate.

Further, the elastic support structure is initially connected to the diaphragm or has a gap.

Further, the elastic support structure is connected with the back plate through a folding beam.

Further, the folding beam comprises a spiral folding structure.

Further, the peripheral region of the diaphragm is fixedly connected to the substrate or the backplate.

Further, the back plate includes a plurality of first through holes communicating with the cavity.

Further, the peripheral region of the diaphragm includes a second through hole communicating with the cavity.

The invention also provides a microphone comprising the capacitive sensor.

The invention has the beneficial effects that:

the elastic support is arranged in the middle of the vibrating diaphragm of the capacitance type sensor structure, so that the rigidity of the middle of the vibrating diaphragm is close to that of the periphery of the vibrating diaphragm, when the sensor works, pressure acts on the vibrating diaphragm, and deformation of each part of the vibrating diaphragm is more uniform, so that a chip has a larger effective area, a higher pull-in voltage and a higher SNR performance.

[ description of the drawings ]

FIG. 1 is a schematic cross-sectional view of a prior art capacitive sensor structure;

FIG. 2 is a schematic cross-sectional view of a capacitive sensor structure according to one embodiment of the present invention;

FIG. 3 is a top view of a capacitive sensor structure in accordance with one embodiment of the present invention;

FIG. 4 is an enlarged schematic view of portion A of FIG. 3 of the present invention;

FIG. 5 is a schematic structural view of a back plate of the present invention;

FIG. 6 is a schematic cross-sectional view of a capacitive sensor structure according to one embodiment of the present invention;

FIG. 7 is a schematic cross-sectional view of a capacitive sensor structure according to one embodiment of the present invention;

fig. 8 is a schematic cross-sectional view of a capacitive sensor structure according to an embodiment of the invention.

[ detailed description ] embodiments

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of the invention, as illustrated in the accompanying drawings.

As shown in fig. 2, a capacitive sensor according to an embodiment of the present invention is prepared by using a MEMS process. When applied to acoustic devices, they are typically MEMS microphones. The capacitive sensor comprises a substrate 1, for example of silicon, glass or other suitable material. A back cavity 2 is formed on the substrate 1. The back cavity 2 may be formed using a body etch process. The capacitance system 3 is arranged on the substrate 1, the capacitance system 3 comprises a back plate 4 and a vibrating diaphragm 5 which are oppositely arranged at intervals, and a cavity 6 is formed between the back plate 4 and the vibrating diaphragm 5; the projection of the cavity 6 onto the substrate 1 overlaps with the majority of the area of the back cavity 2. The first surface 401 of the back plate 4 facing the diaphragm 5 is provided with an elastic support structure 7, and the elastic support structure 7 is arranged in the central area of the back plate 4.

Wherein, backplate 4 and vibrating diaphragm 5 are capacitance sensor's the two poles of the earth, and middle cavity 6 constitutes the capacitance medium, and circular telegram during operation, backplate 4 and vibrating diaphragm 5 can take opposite polarity's electric charge, and when as microphone during operation, under the acoustic wave effect, vibrating diaphragm 5 vibration leads to its and backplate apart from to change to the capacitance value that leads to the electric capacity changes, and then converts the sound wave signal into the signal of telecommunication, realizes the function of microphone.

When the peripheral region of the diaphragm 5 is partly or wholly fixed, during vibration, in the absence of the elastic support structure 7: the maximum amplitude in the central region of the diaphragm 5 may result in the diaphragm adhering to the backplate at a very low voltage, i.e. a low pull-in voltage. The invention adds the elastic supporting structure 7, so that the rigidity of the middle part of the vibrating diaphragm 5 is close to the rigidity of the periphery of the vibrating diaphragm 5, when the sensor works, pressure acts on the vibrating diaphragm, the deformation of each part of the vibrating diaphragm is more uniform, and the chip has larger effective area and higher pull-in voltage, thereby having higher SNR performance.

The elastic support structure 7 has a supporting function and avoids reducing the sensitivity of the device, so the connection mode of the elastic support structure and the back plate 4 is set to be elastic connection.

In particular, as shown in fig. 3-5, the resilient support structure 7 is connected to the back panel 4 via a folding beam 8. The folding beam 8 is, for example, a spiral folding structure, so that the elastic support structure 7 and the back plate 4 are elastically connected to avoid the sensitivity reduction problem caused by rigid connection.

Alternatively, the elastic support structure 7 and the diaphragm 5 may be in a connected state or may leave a gap 9.

Alternatively, as shown in FIGS. 2, 6-7, the peripheral region of the diaphragm 5 may be fixedly attached to the substrate 1; may also be attached to the back plate 4 as shown in fig. 8.

Optionally, as shown in fig. 2, the second surface 402 of the backplate 4 is further provided with a plurality of first through holes 10, the first through holes 10 penetrate through the backplate 4 to communicate with the cavity 6, and the first through holes 10 are, for example, sound inlet holes or release holes.

Optionally, a plurality of anti-adhesion studs 11 are further disposed on the first surface 401 of the back plate 4.

Optionally, a second through hole 12 communicating with the cavity 6 is further included in the peripheral region of the diaphragm.

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

Claims

1. A capacitance type sensor comprises a substrate with a back cavity and a capacitance system arranged on the substrate, wherein the capacitance system comprises a back plate and a vibrating diaphragm which are oppositely arranged at intervals, and a cavity is formed between the back plate and the vibrating diaphragm; the method is characterized in that: the first surface of the back plate facing the vibrating diaphragm is provided with an elastic supporting structure, and the elastic supporting structure is arranged in the central area of the back plate.

2. A capacitive sensor according to claim 1 in which the resilient support structure is initially attached to the diaphragm or has a gap.

3. A capacitive sensor according to claim 1 in which the resilient support structure is connected to the back plate via a folded beam.

4. A capacitive sensor according to claim 3 in which the folded beam comprises a spiral fold.

5. A capacitive sensor according to claim 1 in which the peripheral region of the diaphragm is fixedly attached to the substrate or the backplate.

6. A capacitive sensor according to claim 1 in which the backplate comprises a plurality of first through-holes communicating with the cavity.

7. A capacitive sensor according to claim 5 in which the peripheral region of the diaphragm includes a second through-hole communicating with the cavity.

8. A microphone comprising a capacitive sensor according to any one of claims 1 to 7.