A back-input MEMS microphone structure and its packaging structure

Abstract

The present invention provides a back-to-ear MEMS microphone structure and its packaging structure. The back-to-ear MEMS microphone structure includes a conductive structure located between a diaphragm and a substrate, forming a structural connection between the diaphragm and the substrate. Since both the diaphragm material and the substrate are conductive, an electrical connection is also achieved between the two. The conductive structure may include a first conductive portion located on the outer side wall of the bracket, a second conductive portion located on the inner side wall of the bracket, and may also include a third conductive portion located inside the bracket, which can enhance the electrical connection effect between the diaphragm and the substrate. The packaging structure of the present invention includes a circuit board, a metal packaging shell, the above-mentioned MEMS microphone structure and a dedicated integrated circuit. The packaging structure can realize that the back electrode is located in a Faraday cage composed of a diaphragm, a substrate, a circuit board and a metal packaging shell, thereby effectively shielding external radio frequency interference signals and effectively improving the anti-radio frequency interference capability of the back-to-ear MEMS microphone.

Description

Technical Field

[0001] The present invention belongs to the technical field of microphones and relates to a back-input MEMS microphone structure and a packaging structure thereof. Background Art

[0002] Today's smartphones and smart speakers all use microphones manufactured using micro-electromechanical systems (MEMS) technology. This type of microphone features small size, low power consumption, excellent performance, good consistency, and easy assembly. In practical applications, when mobile phones and wireless IoT devices transmit data, antennas pick up noise in various ways. For example, the diode junction in the application-specific integrated circuit (ASIC) rectifies the radio frequency signal, and the envelope of this rectified signal generates noise in the microphone's output sound. Therefore, a key development trend in MEMS microphones is resistance to radio frequency (RF) interference. The metal packaging of the MEMS microphone itself can provide a certain degree of electromagnetic shielding.

[0003] How to further improve the anti-radio frequency interference capability of MEMS microphones has become an important technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a back-input MEMS microphone structure and a packaging structure thereof, so as to solve the problem of poor radio frequency interference resistance of MEMS microphones in the prior art.

[0005] To achieve the above-mentioned and other related objectives, the present invention provides a back-input MEMS microphone structure, comprising:

[0006] A substrate, wherein the substrate is provided with a cavity penetrating the substrate in a vertical direction;

[0007] a diaphragm suspended above the cavity;

[0008] a bracket, located between the diaphragm and the substrate to support the diaphragm;

[0009] a conductive structure, located between the diaphragm and the substrate to electrically connect the diaphragm and the substrate;

[0010] a backpole, located above the diaphragm, with an air gap between the backpole and the diaphragm, and a plurality of first sound holes vertically penetrating the backpole, the first sound holes being connected to the air gap;

[0011] A back plate is connected to the substrate and the back electrode, and a plurality of second sound holes are provided in the back plate and pass through the back plate in a vertical direction, and the second sound holes are connected to the first sound holes.

[0012] Optionally, the conductive structure is connected to the bracket.

[0013] Optionally, the conductive structure includes a first conductive portion located on an outer side wall of the bracket.

[0014] Optionally, the conductive structure includes a second conductive portion located on the inner side wall of the bracket.

[0015] Optionally, the conductive structure includes a third conductive portion penetrating the bracket in a vertical direction, and a sidewall of the third conductive portion is surrounded by the bracket.

[0016] Optionally, in a direction from the center of the diaphragm to the edge of the diaphragm, the conductive structure includes at least two third conductive parts arranged at intervals from the inside to the outside.

[0017] Optionally, the third conductive portion is a continuous ring structure or a discontinuous ring structure.

[0018] Optionally, the annular structure includes one of a circular ring and a polygonal ring.

[0019] Optionally, the MEMS microphone structure further includes a backpole lead electrode electrically connected to the backpole and a diaphragm lead electrode electrically connected to the diaphragm.

[0020] Optionally, a plurality of blocking blocks are provided on the lower surface of the back plate, the blocking blocks vertically penetrate the back pole, and the lower surface of the blocking blocks is lower than the lower surface of the back pole.

[0021] Optionally, the MEMS microphone structure further includes an air leakage hole, and the air leakage hole passes through the diaphragm in a vertical direction.

[0022] The present invention also provides a packaging structure, comprising:

[0023] A circuit board, wherein the circuit board is provided with a sound inlet hole that passes through the circuit board in a vertical direction;

[0024] A metal packaging shell is connected to the circuit board and forms a receiving space with the circuit board;

[0025] The MEMS microphone structure as described in any one of the above items is located in the receiving space, the substrate is connected to the circuit board, and the cavity is connected to the sound inlet;

[0026] A dedicated integrated circuit is located in the receiving space and is electrically connected to the MEMS microphone structure.

[0027] As described above, the back-to-ear MEMS microphone structure of the present invention includes a conductive structure located between the diaphragm and the substrate, forming a structural connection between the diaphragm and the substrate. Since both the diaphragm material and the substrate are conductive, an electrical connection is also achieved between the two. The conductive structure may include a first conductive portion located on the outer side wall of the bracket, a second conductive portion located on the inner side wall of the bracket, and may also include a third conductive portion located inside the bracket, which can strengthen the electrical connection effect between the diaphragm and the substrate. After packaging, the back-to-ear MEMS microphone structure of the present invention can realize that the back electrode is located in a Faraday cage composed of the diaphragm, substrate, circuit board and metal packaging shell, thereby effectively shielding external radio frequency interference signals and effectively improving the anti-radio frequency interference capability of the back-to-ear MEMS microphone. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic cross-sectional structure diagram of the back-input sound MEMS microphone structure of the present invention.

[0029] Figure 2 Shown is a planar layout diagram of the conductive structure and the diaphragm.

[0030] Figure 3 Shown is a second planar layout diagram of the conductive structure and the diaphragm.

[0031] Figure 4 Shown is a third planar layout diagram of the conductive structure and the diaphragm.

[0032] Figure 5 Shown is a fourth planar layout diagram of the conductive structure and the diaphragm.

[0033] Figure 6 Shown is a schematic diagram of the packaging structure of the present invention.

[0034] Component number description

[0035] 1 substrate

[0036] 2 diaphragms

[0037] 3 brackets

[0038] 4 Conductive structure

[0039] 401 first conductive part

[0040] 402 second conductive portion

[0041] 403 third conductive portion

[0042] 5 Dorsal Pole

[0043] 6 vent holes

[0044] 7 Back Panel

[0045] 8 Cavity

[0046] 9 Air Gap

[0047] 10 First sound hole

[0048] 11 Second sound hole

[0049] 12 Back electrode lead-out electrode

[0050] 13 Diaphragm lead-out electrode

[0051] 14 Blocks

[0052] 15 Containment Space

[0053] 16 Circuit Board

[0054] 17 Metal package shell

[0055] 18 ASIC

[0056] 19 Sound inlet

[0057] 20 wires DETAILED DESCRIPTION

[0058] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0059] See also Figures 1 to 6 It should be noted that the diagrams provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the diagrams only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0060] Example 1

[0061] The present invention provides a back-input MEMS microphone structure. Figure 1, which is a schematic cross-sectional structure diagram of the back-entry MEMS microphone structure, including a substrate 1, a diaphragm 2, a bracket 3, a conductive structure 4, a back electrode 5 and a back plate 7, wherein the substrate 1 is provided with a cavity 8 that passes through the substrate 1 in a vertical direction; the diaphragm 2 is suspended above the cavity 8; the bracket 3 is located between the diaphragm 2 and the substrate 1 to support the diaphragm 2; the conductive structure 4 is located between the diaphragm 2 and the substrate 1 to electrically connect the diaphragm 2 and the substrate 1; the back electrode 5 is located above the diaphragm 2, and there is an air gap 9 between the back electrode 5 and the diaphragm 2, the back electrode 5 is provided with a plurality of first sound holes 10 that pass through the back electrode 5 in a vertical direction, and the first sound holes 10 are connected to the air gap 9; the back plate 7 is connected to the substrate 1 and the back electrode 5, and the back plate 5 is provided with a plurality of second sound holes 11 that pass through the back plate 5 in a vertical direction, and the second sound holes 11 are connected to the first sound holes 10.

[0062] Specifically, the diaphragm 2, the air gap 9 and the back pole 5 are used to form a capacitor structure. When the microphone is working, the sound signal can enter the capacitor structure (inside the air gap 9) through the second sound hole 11 and the first sound hole 10, and can also enter the capacitor structure through the cavity 8, so that the distance between the diaphragm 2 and the back pole 5 changes, thereby causing the capacitance value of the capacitor structure to change accordingly, and then converting the sound signal into an electrical signal.

[0063] Specifically, substrate 1 provides a process platform for forming a MEMS microphone structure, and may include, but is not limited to, a silicon substrate, a germanium substrate, a silicon-germanium substrate, a silicon carbide substrate, or a III-V compound substrate (e.g., a gallium nitride substrate or a gallium arsenide substrate). Substrate 1 may be made conductive to a certain extent through doping or other means. In this embodiment, substrate 1 is exemplified by a silicon substrate.

[0064] Specifically, the diaphragm 2 is used to vibrate under the air pressure generated by sound, and its material includes but is not limited to polysilicon. The diaphragm 2 can have a certain degree of conductivity through doping or the like.

[0065] Specifically, the bracket 3 is used to support the diaphragm 2 , and its material includes but is not limited to silicon oxide.

[0066] Specifically, the conductive structure 4 forms a structural connection between the diaphragm 2 and the substrate 1 . Since the material of the diaphragm 2 and the material of the substrate 1 are both conductive, an electrical connection is achieved between the two through the conductive structure 4 .

[0067] As an example, the conductive structure 4 and the bracket 3 can be provided separately or connected to each other. In this embodiment, the conductive structure 4 is preferably connected to the bracket 3.

[0068] As an example, the conductive structure 4 can be made of the same material as the diaphragm 2, such as polysilicon, and can be manufactured simultaneously with the diaphragm 2 to simplify the manufacturing process.

[0069] As an example, the conductive structure 4 may include a first conductive portion 401 located on an outer sidewall of the bracket 3 , and may include a second conductive portion 402 located on an inner sidewall of the bracket.

[0070] As an example, the conductive structure 4 may further include a third conductive portion 403 vertically extending through the bracket 3, with the sidewalls of the third conductive portion 403 surrounded by the bracket 3. The conductive layer within the bracket can enhance the electrical connection between the diaphragm 2 and the substrate 1 based on the conductive layer on the bracket sidewalls.

[0071] As an example, in a direction from the center of the diaphragm 2 toward the edge of the diaphragm 2, the conductive structure 4 may include one third conductive portion 403, or may include at least two third conductive portions 403 spaced apart from each other from the inside out. In other words, to achieve a better electrical connection, the number of horizontal layers of the third conductive portions 403 within the bracket may be appropriately increased.

[0072] As an example, see Figure 2 , which shows a planar layout diagram of the conductive structure 4 and the diaphragm 2, wherein: Figure 2 The conductive structure 4 shown here includes a third conductive portion 403, extending from the center of the diaphragm 2 toward the edge of the diaphragm 2. The conductive structure 4, consisting of the first conductive portion 401, the third conductive portion 403, and the second conductive portion 402, forms a three-ring structure. If the third conductive portion 403 has multiple horizontal layers, the conductive structure 4 will form at least a four-ring structure.

[0073] As an example, the third conductive portion 4 may be a continuous ring structure or a discontinuous ring structure, and the ring structure includes but is not limited to a circular ring or a polygonal ring. The same applies to the first conductive portion 104 and the second conductive portion 402. Figure 2 The first conductive portion 401 , the third conductive portion 403 , and the second conductive portion 402 are all continuous square rings.

[0074] As an example, see Figure 3 , which shows a second planar layout diagram of the conductive structure 4 and the diaphragm 2, wherein the first conductive portion 401, the third conductive portion 403 and the second conductive portion 402 are all continuous circular rings.

[0075] As an example, see Figure 4, which shows a third planar layout diagram of the conductive structure 4 and the diaphragm 2, wherein the first conductive portion 401, the third conductive portion 403 and the second conductive portion 402 are all discontinuous square rings.

[0076] As an example, see Figure 5 , which shows a fourth planar layout diagram of the conductive structure 4 and the diaphragm 2 , wherein the first conductive portion 401 , the third conductive portion 403 and the second conductive portion 402 are all discontinuous circular rings.

[0077] It should be noted that, in other embodiments, the annular structure layout and the number of layers in the horizontal direction of the third conductive structure 4 can be adjusted as needed and are not limited to the above embodiment.

[0078] As an example, see Figure 1 The MEMS microphone structure further includes a back electrode lead electrode 12 electrically connected to the back electrode 5 and a diaphragm lead electrode 13 electrically connected to the diaphragm 2. The material of the back electrode 5 includes, but is not limited to, polysilicon. The back electrode lead electrode 12 and the diaphragm lead electrode 13 are made of a conductive material, such as a conductive metal.

[0079] As an example, a plurality of blocking blocks 14 are provided on the lower surface of the back plate 5 , and the blocking blocks 14 pass through the back pole 5 in the vertical direction, and the lower surface of the blocking blocks 14 is lower than the lower surface of the back pole 5 to prevent the diaphragm 2 from adhering to the back pole 5 .

[0080] As an example, the MEMS microphone structure further includes bleed holes 6 that vertically penetrate the diaphragm 2. These bleed holes 6 are used to release air through them when the diaphragm 2 is subjected to high pressure, thereby reducing the pressure on the diaphragm 2. The number and distribution of the bleed holes 6 can be adjusted as needed.

[0081] The back-firing MEMS microphone structure of this embodiment includes a conductive structure located between the diaphragm and the substrate, forming a structural connection between the diaphragm and the substrate. Because both the diaphragm material and the silicon substrate are conductive, they also achieve electrical connection. The conductive structure can include a first conductive portion located on the outer sidewall of the bracket, a second conductive portion located on the inner sidewall of the bracket, and a third conductive portion located within the bracket, thereby strengthening the electrical connection between the diaphragm and the substrate.

[0082] Example 2

[0083] This embodiment provides a packaging structure. Figure 6, which is a schematic diagram of the packaging structure, includes a circuit board 16, a metal packaging shell 17, the MEMS microphone structure as described in Example 1, and an application-specific integrated circuit 18, wherein the circuit board 16 is provided with a sound inlet hole 19 that passes through the circuit board 16 in a vertical direction; the metal packaging shell 17 is connected to the circuit board 16 and together with the circuit board 16, forms a receiving space 15; the MEMS microphone structure is located in the receiving space 15, the substrate 1 of the MEMS microphone structure is connected to the circuit board 16, and the cavity 8 is in communication with the sound inlet hole 19; the application-specific integrated circuit 18 is located in the receiving space 15 and is electrically connected to the MEMS microphone structure, for example, via a wire 20.

[0084] The packaging structure of this embodiment can realize that the back pole 5 of the MEMS microphone structure is located in a Faraday cage composed of the diaphragm 2, substrate 1, circuit board 16 and metal packaging shell 17, thereby effectively shielding external radio frequency interference signals and effectively improving the anti-radio frequency interference capability of the back-to-back MEMS microphone.

[0085] In summary, the back-to-ear sound MEMS microphone structure of the present invention includes a conductive structure located between the diaphragm and the substrate, forming a structural connection between the diaphragm and the substrate. Since both the diaphragm material and the substrate are conductive, an electrical connection is also achieved between the two. Among them, the conductive structure may include a first conductive part located on the outer side wall of the bracket, a second conductive part located on the inner side wall of the bracket, and may also include a third conductive part located inside the bracket, which can enhance the electrical connection effect between the diaphragm and the substrate. After packaging, the back-to-ear sound MEMS microphone structure of the present invention can realize that the back pole is located in a Faraday cage composed of the diaphragm, substrate, circuit board and metal packaging shell, thereby effectively shielding external radio frequency interference signals and effectively improving the anti-radio frequency interference capability of the back-to-ear sound MEMS microphone. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial utilization value.

[0086] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A back-input MEMS microphone structure, characterized in that: include: A substrate, wherein the substrate is provided with a cavity penetrating the substrate in a vertical direction; a diaphragm suspended above the cavity; a bracket, located between the diaphragm and the substrate to support the diaphragm; a conductive structure, located between the diaphragm and the substrate to electrically connect the diaphragm and the substrate; a backpole, located above the diaphragm, with an air gap between the backpole and the diaphragm, and a plurality of first sound holes vertically penetrating the backpole, the first sound holes being connected to the air gap; a back plate connected to the substrate and the back electrode, wherein the back plate is provided with a plurality of second sound holes penetrating the back plate in a vertical direction, wherein the second sound holes are connected to the first sound holes; The conductive structure is connected to the bracket; the conductive structure includes a first conductive part located on the outer side wall of the bracket, a second conductive part located on the inner side wall of the bracket, and a third conductive part that passes through the bracket in a vertical direction, and the side wall of the third conductive part is surrounded by the bracket; in the direction from the center of the diaphragm to the edge of the diaphragm, the conductive structure includes at least two third conductive parts arranged at intervals from the inside to the outside.

2. The back-input MEMS microphone structure according to claim 1, wherein: The third conductive portion is in a continuous ring structure or a discontinuous ring structure.

3. The back-input MEMS microphone structure according to claim 2, wherein: The annular structure includes one of a circular ring and a polygonal ring.

4. The back-input MEMS microphone structure according to claim 1, wherein: The MEMS microphone structure further includes a back electrode lead-out electrode electrically connected to the back electrode and a diaphragm lead-out electrode electrically connected to the diaphragm.

5. The back-input MEMS microphone structure according to claim 1, wherein: A plurality of blocking blocks are provided on the lower surface of the back plate. The blocking blocks penetrate the back electrode in a vertical direction, and the lower surface of the blocking blocks is lower than the lower surface of the back electrode.

6. The back-input MEMS microphone structure according to claim 1, wherein: The MEMS microphone structure further includes an air leakage hole, which passes through the diaphragm in a vertical direction.

7. A packaging structure, characterized in that: include: A circuit board, wherein the circuit board is provided with a sound inlet hole that passes through the circuit board in a vertical direction; A metal packaging shell is connected to the circuit board and forms a receiving space with the circuit board; The MEMS microphone structure according to any one of claims 1 to 6, located in the receiving space, the substrate is connected to the circuit board, and the cavity is connected to the sound inlet; an application-specific integrated circuit, located in the receiving space and electrically connected to the MEMS microphone structure; The back electrode is located in a Faraday cage composed of the diaphragm, substrate, circuit board and metal packaging shell.

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