Microphone Chip and Its Packaging Structure

Abstract

The present invention provides a microphone chip and its packaging structure to solve the problem that the application scenarios of microphones based on the air-borne principle are limited in the prior art. The microphone chip includes a vibration acquisition unit, a conversion unit, and a first cavity located between the vibration acquisition unit and the conversion unit; wherein, the vibration acquisition unit converts the skull vibration generated by sound into mechanical vibration; the gas in the first cavity is compressed under the action of the mechanical vibration; and the conversion unit converts the compression signal of the gas into an electrical signal for output.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and particularly to a microphone chip and its packaging structure. Background Art

[0002] Sound waves have two propagation modes, namely air propagation and skull bone propagation. Most traditional microphones collect sound signals based on the air propagation principle. However, since the air propagation mode is greatly affected by the environment, the application scenarios of traditional microphones are limited. Therefore, it is necessary to provide a new type of microphone based on skull bone propagation. Summary of the Invention

[0003] In view of this, embodiments of the present invention are committed to providing a microphone chip and its packaging structure to solve the problem that the application scenarios of microphones based on the air propagation principle in the prior art are limited.

[0004] The first aspect of the present invention provides a microphone chip, including a vibration acquisition unit, a conversion unit, and a first cavity located between the vibration acquisition unit and the conversion unit. The vibration acquisition unit converts the skull vibration generated by sound into mechanical vibration; the gas in the first cavity is compressed under the action of the mechanical vibration; the conversion unit converts the compression signal of the gas into an electrical signal for output.

[0005] In one embodiment, the vibration acquisition unit includes a first diaphragm and a mass block located on the side of the first diaphragm away from the first cavity.

[0006] In one embodiment, the thickness of the first diaphragm is 2 - 20 microns; and / or the thickness of the mass block is 20% - 80% of the thickness of the cavity accommodating the mass block.

[0007] In one embodiment, the conversion unit includes a second diaphragm and a back plate, and a second cavity located between the second diaphragm and the back plate.

[0008] In one embodiment, the back plate is located between the first cavity and the second cavity, and the back plate includes at least one first through hole communicating the first cavity and the second cavity.

[0009] In one embodiment, at least one first through hole includes a plurality of first through holes, and the plurality of first through holes are uniformly arranged on the back plate.

[0010] In one embodiment, at least one of the surface of the back plate close to the first cavity and the surface close to the second cavity includes a protrusion.

[0011] In one embodiment, the second diaphragm includes a second through hole, and the second through hole penetrates the second diaphragm in the thickness direction.

[0012] In one embodiment, the first diaphragm, the back plate, and the second diaphragm are arranged in parallel in sequence.

[0013] In one embodiment, the distance between the first diaphragm and the back plate is greater than the distance between the back plate and the second diaphragm.

[0014] A second aspect of the present invention provides a packaging structure for a microphone chip, including: a substrate and a housing, with a receiving cavity between the substrate and the housing; and the microphone chip provided in any of the above embodiments fixed in the receiving cavity and an integrated circuit chip electrically connected to the microphone chip.

[0015] According to the microphone chip and its packaging structure provided by the embodiments of the present invention, a bone conduction microphone chip is provided, which collects cranial vibrations through a vibration acquisition unit. The cranial vibrations are transmitted to a conversion unit in the form of compressed gas, and the conversion unit converts the compressed signal of the gas into an electrical signal, thereby realizing the acquisition of sound signals through the bone conduction principle. Description of the Drawings

[0016] Figure 1 It is a three-dimensional cross-sectional schematic diagram of a microphone chip provided by an embodiment of the present invention.

[0017] Figure 2 is Figure 1 a cross-sectional schematic diagram of the shown microphone chip.

[0018] Figure 3 It is a schematic diagram of a packaging structure of a microphone chip provided by an embodiment of the present invention. Detailed Embodiments

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] Figure 1 It is a three-dimensional cross-sectional schematic diagram of a microphone chip provided by an embodiment of the present invention. Figure 2 is Figure 1 a cross-sectional schematic diagram of the shown microphone chip. Combining Figure 1 and Figure 2 it can be seen that the microphone chip 100 includes a vibration acquisition unit 103, a conversion unit, and a first cavity A located between the vibration acquisition unit 103 and the conversion unit. The vibration acquisition unit 103 converts the cranial vibrations generated by sound into mechanical vibrations; the gas in the first cavity A is compressed under the action of the mechanical vibrations; the conversion unit converts the compressed signal of the gas into an electrical signal for output.

[0021] In one embodiment, the vibration acquisition unit 103 includes a first diaphragm 103a and a mass block 103b located on the side of the first diaphragm 103a away from the first cavity A. The mass block 103b senses the vibration of the skull to generate mechanical vibration, and the mechanical vibration of the mass block 103b drives the first diaphragm 103a to squeeze the gas in the first cavity A. Subsequently, the conversion unit converts the compression signal of the gas into an electrical signal for output.

[0022] By adjusting the width or height of the mass block 103b, the size of the mass block 103b can be changed. The size of the mass block 103b is one of the key factors affecting the sensitivity of the vibration acquisition unit 103. The smaller the mass block 103b, the higher the sensitivity of the vibration acquisition unit 103. The material of the first diaphragm 103a includes polysilicon. By adjusting the surface area, thickness of the first diaphragm 103a, and the cross-sectional area of the mass block in the direction parallel to the first diaphragm 103a, the stiffness of the microphone chip 100 can be changed.

[0023] The thickness selection of the first diaphragm 103a and the mass block 103b restricts each other. Generally speaking, the thickness of the first diaphragm 103a is positively correlated with the thickness of the mass block 103b. In one embodiment, as Figure 2 shown, the thickness D1 of the first diaphragm 103a is 2 - 20 microns, and the thickness D2 of the mass block 103b is 20% - 80% of the thickness D3 of the cavity C that houses the mass block 103b. Preferably, the thickness D2 of the mass block 103b is 50% - 80% of the thickness D3 of the cavity C that houses the mass block 103b.

[0024] In one embodiment, the conversion unit includes a second diaphragm 108, a back plate 105, and a second cavity B located between the second diaphragm 108 and the back plate 105. After the gas in the first cavity A is compressed, the second diaphragm 108 generates a displacement, thereby changing the capacitance between the second diaphragm 108 and the back plate 105, and the change in capacitance generates an electrical signal. In this case, for the overall structure of the microphone chip, the mass block 103b and the second diaphragm 108 are separately provided. Compared with the prior art structure in which the mass block and the diaphragm are integrally formed, the following beneficial effects can be achieved. First, in terms of material selection, in the prior art, since the mass block and the diaphragm are integrally formed, the mass block needs to meet both the vibration requirements and the conductive requirements of the diaphragm; while in the present application, since the mass block 103b and the second diaphragm 108 are separately provided, the mass block 103b only needs to meet the vibration requirements. Therefore, the material selection of the mass block 103b in the microphone chip of the present application is more flexible. Second, for the prior art structure in which the mass block and the diaphragm are integrally formed, due to process requirements, several holes, such as release holes, are usually formed in the diaphragm. Due to the existence of these holes, cracks are easily generated during the vibration of the diaphragm, resulting in low reliability of the diaphragm. In the present application, the mass block 103b and the second diaphragm 108 are separately provided, thereby greatly reducing the problem of crack generation in the second diaphragm 108 and improving the reliability of the diaphragm. The sizes of the first cavity A and the second cavity B are one of the important factors affecting the sensitivity of the microphone chip 100. The larger the sum of the volumes of the first cavity A and the second cavity B, the higher the sensitivity of the microphone chip 100.

[0025] According to the microphone chip provided in this embodiment, a bone conduction microphone chip is provided. The vibration acquisition unit 103 collects the vibration of the skull, and the vibration of the skull is transmitted to the conversion unit in the form of compressed gas. The conversion unit converts the compressed signal of the gas into an electrical signal, thereby realizing the acquisition of sound signals through the bone conduction principle.

[0026] In one embodiment, as Figure 1 and Figure 2 shown, the back plate 105 is located between the first cavity A and the second cavity B. The back plate 105 includes at least one first through hole 105b communicating the first cavity A and the second cavity B. When the back plate 105 includes a connection between the first cavity A and the second cavity B, it is necessary to form a first through hole 105b in the back plate 105 to ensure that the compression of the gas in the first cavity A can be transmitted to the gas in the first cavity A, and then the second diaphragm 108 vibrates.

[0027] According to the microphone chip provided in this embodiment, by disposing the back plate 105 between the first cavity A and the second cavity B, compared with disposing the second diaphragm 108 between the first cavity A and the second cavity B, the former can avoid the problem of easy adhesion caused by the adjacent two diaphragms. At the same time, since at least one first through hole 105b is formed on the back plate 105, therefore, according to this embodiment, by disposing the back plate 105 between the first cavity A and the second cavity B, compared with disposing the second diaphragm 108 between the first cavity A and the second cavity B, the sealing performance of the first cavity A and the second cavity B is better, so that a good dust-proof effect can be achieved, thereby avoiding the adverse effect of dust on the vibration of the second diaphragm 108 and / or the first diaphragm 103a and ensuring the device accuracy. In one embodiment, at least one first through hole 105b includes a plurality of first through holes 105b, and the plurality of first through holes 105b are uniformly arranged on the back plate 105.

[0028] The shape of the first through hole 105b can be arbitrary, such as a round hole, a square hole, a triangular hole, etc. The larger the volume ratio of the first through hole 105b on the back plate 105, the smaller the impedance, the lower frequency part will attenuate, the smaller the wind noise, and the better the reliability of the microphone chip.

[0029] According to the microphone chip provided in this embodiment, by arranging a plurality of first through holes 105b to be uniformly arranged on the back plate 105, it can ensure that the pressure of the gas in the first cavity A is uniformly applied to the gas in the second cavity B, thereby avoiding the concentrated force on the second diaphragm 108, and further improving the reliability of the microphone chip.

[0030] In one embodiment, at least one of the surface of the back plate 105 close to the first cavity A and the surface close to the second cavity B includes a protrusion 105a.

[0031] The shape and height of the protrusion 105a are adjustable. The protrusion 105a has a limiting effect, which can prevent the amplitude of the first diaphragm 103a and / or the second diaphragm 108 from being too large, and the contact area between the first diaphragm 103a and / or the second diaphragm 108 and the protrusion 105a is smaller than the contact area between the first diaphragm 103a and / or the second diaphragm 108 and the back plate 105, thereby effectively preventing film adhesion.

[0032] In one embodiment, the second diaphragm 108 includes a second through hole, and the second through hole penetrates the second diaphragm 108 in the thickness direction. The second through hole includes two types, namely an air leakage hole 108a and a release hole 108b.

[0033] Among them, the air vent 108a is used to balance the gas pressure received by the second diaphragm 108, thereby preventing the second diaphragm 108 from rupturing due to excessive concentration of gas pressure. The shape of the air vent 108a includes any one of strip-shaped, U-shaped, circular, and square. The air vent 108a can be arranged at the peripheral edge or the central position of the second diaphragm 108. The number of air vents 108a can be reasonably set according to actual needs. In one embodiment, the number of air vents 108a is multiple, and the multiple air vents 108a are arranged around the center of the second diaphragm 108.

[0034] The release hole 108b is for process requirements and is used to remove the sacrificial layer to form the second cavity B and / or the first cavity A. The shape of the release hole 108b includes any one of strip-shaped, U-shaped, circular, and square. The release hole 108b can be arranged at the peripheral edge or the central position of the second diaphragm 108. The number of release holes 108b can be reasonably set according to actual needs. In one embodiment, the number of release holes 108b is one, and one air vent 108a is arranged at the center of the second diaphragm 108.

[0035] In one embodiment, the first diaphragm 103a, the back plate 105, and the second diaphragm 108 are arranged in parallel in sequence.

[0036] For example, as Figure 1 and Figure 2 shown, the microphone chip 100 includes a substrate 101, and the substrate 101 includes an annular through hole that penetrates the substrate 101 in the thickness direction. A first annular sacrificial layer 102 surrounding the annular through hole is provided on the upper surface of the substrate 101. The first diaphragm 103a is suspended on the first annular sacrificial layer 102, and the mass block 103b is located in the annular through hole. A second annular sacrificial layer 104 is provided on the upper surface of the first diaphragm 103a, and the back plate 105 is suspended on the second annular sacrificial layer 104 to form a first cavity A between the back plate 105 and the first diaphragm 103a. A third annular sacrificial layer 107 is provided on the upper surface of the back plate 105, and the second diaphragm 108 is suspended on the third annular sacrificial layer 107 to form a second cavity B between the back plate 105 and the second diaphragm 108. In this embodiment, the surface of the mass block 103b away from the first diaphragm 103a senses the vibration of the skull, and this vibration is sequentially transmitted through the vibration acquisition unit 103, the gas in the first cavity A and the second cavity B, and the conversion of the conversion unit to generate an electrical signal.

[0037] The materials of the first annular sacrificial layer 102, the second annular sacrificial layer 104, and the third annular sacrificial layer 107 mentioned here can be silicon oxide. In addition, the back plate 105 can be a single film layer or a composite film layer formed by stacking multiple film layers. In one embodiment, as Figure 1As shown, the microphone chip 100 further includes another back plate 106 stacked on the side of the back plate 105 close to the second cavity B.

[0038] In one embodiment, the distance between the first diaphragm 103a and the back plate 105 is greater than the distance between the back plate 105 and the second diaphragm 108, that is, for Figure 1 and Figure 2 the shown microphone chip 100, the thickness of the second annular sacrificial layer 104 is greater than the thickness of the third annular sacrificial layer 107. On the premise that the sum of the volumes of the first cavity A and the second cavity B is constant, by setting the distance between the first diaphragm 103a and the back plate 105 to be greater than the distance between the back plate 105 and the second diaphragm 108, on the one hand, the probability of collision between the mass block 103b and the back plate 105 can be further reduced, improving the reliability; on the other hand, the volume of the first cavity A can be increased. Since under the premise that the pressure in the cavity is constant, when a certain pressure is applied to the cavity, the smaller the volume of the cavity, the smaller the deformation, and the larger the volume, the larger the deformation. Therefore, when the volume of the first cavity A increases, the sensitivity of the first diaphragm 103a can be improved.

[0039] The thicknesses of the second annular sacrificial layer 104 and the third annular sacrificial layer 107 are both adjustable. The thinner at least one of the thickness of the second annular sacrificial layer 104 and the thickness of the third annular sacrificial layer 107 is, the higher the sensitivity of the microphone chip 100, but at the same time, it will bring the disadvantage of high noise. Therefore, the optimal signal-to-noise ratio can be achieved by optimizing the parameters through experiments.

[0040] In one embodiment, the microphone chip 100 is a Micro Electromechanical System (MEMS) microphone chip. In this case, the first cavity A and the second cavity B can be made as small as possible, so that the pressure transmitted to the second diaphragm 108 is relatively large, and thus the microphone chip 100 has a high sensitivity.

[0041] It should be noted that according to any embodiment of the present invention, the mass block 103b of the microphone chip is arranged on the first diaphragm 103a. Compared with the technical solution of directly arranging the mass block 103b on the second diaphragm 108 and omitting the first diaphragm 103a at the same time, the advantage is that there are more adjustable design parameters, making the design margin wider, so that microphone chips with different requirements can be realized according to different application scenarios.

[0042] Figure 3 It is a schematic diagram of the packaging structure of the microphone chip provided by an embodiment of the present invention. As Figure 3As shown, the packaging structure 200 of the microphone chip includes a substrate 201 and a housing 204, and there is a receiving cavity between the substrate 201 and the housing 204. The packaging structure 200 further includes a microphone chip 203 fixed in the receiving cavity and an integrated circuit chip 202 electrically connected to the microphone chip 203. The microphone chip 203 is the microphone chip 203 provided by any embodiment of the present invention. The integrated circuit chip 202 is used to process the electrical signal output by the bone conduction microphone chip 203 to convert it into an analog or digital signal.

[0043] In one embodiment, as Figure 3 shown, the microphone chip 203 and the integrated circuit chip 202 are fixed on the substrate 201, and the microphone chip 203 and the integrated circuit chip 202 are interconnected through wire bonding.

[0044] The packaging structure 200 of the microphone chip provided according to this embodiment has the corresponding technical effects to those of the microphone chip 203, which will not be elaborated here.

[0045] The above description has been given for purposes of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions, and sub-combinations thereof.

Claims

1. A microphone chip, characterized in that, It includes a vibration acquisition unit, a conversion unit, and a first cavity located between the vibration acquisition unit and the conversion unit; Among them, the vibration acquisition unit converts the skull vibration generated by sound into mechanical vibration; the gas in the first cavity is compressed under the action of the mechanical vibration; the conversion unit converts the compression signal of the gas into an electrical signal for output; The vibration acquisition unit includes a first diaphragm and a mass block located on the side of the first diaphragm away from the first cavity; the mass block generates mechanical vibration according to the skull vibration, and the mechanical vibration drives the first diaphragm to squeeze the gas in the first cavity; The conversion unit includes a second diaphragm and a back plate, and a second cavity located between the second diaphragm and the back plate; after the gas in the first cavity is compressed, the second diaphragm generates displacement to change the capacitance between the second diaphragm and the back plate, and the change in capacitance generates an electrical signal.

2. The microphone chip according to claim 1, characterized in that, The thickness of the first diaphragm is 2-20 microns; and / or The thickness of the mass block is 20%-80% of the thickness of the cavity accommodating the mass block.

3. The microphone chip according to claim 1, characterized in that, The back plate is located between the first cavity and the second cavity, and the back plate includes at least one first through hole communicating the first cavity and the second cavity.

4. The microphone chip according to claim 3, characterized in that, The at least one first through hole includes a plurality of the first through holes, and the plurality of the first through holes are uniformly arranged on the back plate.

5. The microphone chip according to claim 1, characterized in that, At least one of the surface of the back plate close to the first cavity and the surface close to the second cavity includes a protrusion.

6. The microphone chip according to claim 1, characterized in that, The second diaphragm includes a second through hole, and the second through hole penetrates the second diaphragm in the thickness direction.

7. The microphone chip according to claim 1, characterized in that, The first diaphragm, the back plate, and the second diaphragm are arranged in parallel in sequence.

8. The microphone chip according to claim 7, characterized in that, The distance between the first diaphragm and the back plate is greater than the distance between the back plate and the second diaphragm.

9. An encapsulation structure of a microphone chip, characterized in that, It includes: a substrate and a housing, and there is an accommodation cavity between the substrate and the housing; and a microphone chip according to any one of claims 1-8 fixed in the accommodation cavity and an integrated circuit chip electrically connected to the microphone chip.

Images