MEMS microphone, electronic device, and preparation method for MEMS microphone

Abstract

A MEMS microphone, an electronic device, and a preparation method for the MEMS microphone. The MEMS microphone comprises a substrate, a first diaphragm, a back electrode and a second diaphragm, wherein a sound cavity is formed in the substrate; the back electrode is arranged on the substrate; a first support structure is provided on the side of the back electrode that faces the first diaphragm; a second support structure is provided on the side of the back electrode that is away from the first diaphragm; the second diaphragm is arranged on the back electrode; a second gap is formed between the second diaphragm and the back electrode; and the first diaphragm and / or the second diaphragm are / is a graphene diaphragm.

Description

MEMS microphone, electronic device, and method for manufacturing MEMS microphone

[0001] This disclosure claims priority to Chinese patent application number 202310722140.9, filed with the Patent Office of China on June 16, 2023, entitled “MEMS microphone, electronic device and method for manufacturing MEMS microphone,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to a MEMS microphone, an electronic device, and a method for manufacturing a MEMS microphone. Background Art

[0003] In the existing technology, SDM (Sealed Dual Diaphragm Microphone) is continuously expanding its market share due to its superior high performance, such as signal-to-noise ratio and maximum sound pressure level.

[0004] However, due to many issues such as large internal chip size, complex chip manufacturing process, and lack of reliability, SDM has high cost and limited its application range. Therefore, it is necessary to provide a new MEMS microphone, electronic device and MEMS microphone manufacturing method.

[0005] Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present disclosure is to provide a new technical solution for a MEMS microphone, an electronic device, and a method for manufacturing a MEMS microphone.

[0007] According to one aspect of the present disclosure, a MEMS microphone is provided. The MEMS microphone comprises:

[0008] a substrate having an acoustic cavity formed thereon;

[0009] a first diaphragm, the first diaphragm comprising a fixed portion and a suspended portion, the fixed portion being disposed on the substrate, and the suspended portion being opposite to the acoustic cavity;

[0010] a backpole, the backpole being disposed on the substrate, a first gap being formed between the backpole and the first diaphragm, a first supporting structure being disposed on a side of the backpole facing the first diaphragm, the first supporting structure extending toward the first diaphragm and opposite to the suspended portion, and a second supporting structure being disposed on a side of the backpole away from the first diaphragm;

[0011] a second diaphragm, wherein the second diaphragm is disposed on a back pole, a second gap is formed between the second diaphragm and the back pole, the second supporting structure extends toward the second diaphragm and is opposite to the second diaphragm, and the first diaphragm and / or the second diaphragm is a graphene diaphragm;

[0012] When the MEMS microphone is powered on, the first supporting structure abuts against the suspended portion, and the second supporting structure abuts against the second diaphragm.

[0013] Optionally, the graphene diaphragm includes at least one graphene material layer.

[0014] Optionally, the graphene diaphragm has a thickness ranging from 0.3 nanometers to 100 nanometers.

[0015] Optionally, both the first gap and the second gap are vacuum gaps.

[0016] Optionally, the second diaphragm is a graphene diaphragm.

[0017] Optionally, the material of the first diaphragm is the same as the material of the second diaphragm.

[0018] Optionally, the material of the first diaphragm is different from the material of the second diaphragm.

[0019] Optionally, the first supporting structure and the second supporting structure are arranged on two sides of the back pole opposite to each other.

[0020] Optionally, a third gap is provided between the first supporting structure and the first diaphragm, and a fourth gap is provided between the second supporting structure and the second diaphragm.

[0021] Optionally, the MEMS microphone is a differential pressure microphone.

[0022] According to another aspect of the present disclosure, an electronic device is provided, comprising any one of the above-mentioned MEMS microphones.

[0023] According to another aspect of the present disclosure, a method for preparing a MEMS microphone is provided. The method comprises:

[0024] Make the base;

[0025] Depositing a first diaphragm and a first supporting structure in sequence on the substrate;

[0026] Depositing a back electrode and a second supporting structure in sequence on the first supporting structure;

[0027] A second diaphragm is deposited on the second supporting structure, the first diaphragm and the second diaphragm are connected, and the first diaphragm and / or the second diaphragm is a graphene diaphragm.

[0028] Optionally, the step of sequentially depositing a first diaphragm and a first supporting structure on the substrate; sequentially depositing a back electrode and a second supporting structure on the first supporting structure; and depositing a second diaphragm on the second supporting structure comprises:

[0029] Depositing a first diaphragm on the substrate, wherein the first diaphragm is a polysilicon layer or is formed on a first sacrificial layer;

[0030] depositing a first support structure on the first diaphragm;

[0031] depositing a second sacrificial layer, wherein the second sacrificial layer is flush with the first support structure;

[0032] depositing a back electrode on the second sacrificial layer;

[0033] Depositing a third sacrificial layer, wherein the third sacrificial layer is flush with the back electrode;

[0034] depositing a second support structure on the third sacrificial layer;

[0035] depositing a fourth sacrificial layer, wherein the fourth sacrificial layer is flush with the second support structure;

[0036] depositing a fifth sacrificial layer;

[0037] Growing graphene, growing graphene on the fifth sacrificial layer, or growing graphene both below the first sacrificial layer and above the fifth sacrificial layer;

[0038] Release the sacrificial layer and obtain the MEMS microphone.

[0039] Optionally, releasing the sacrificial layer and obtaining the MEMS microphone includes:

[0040] The first sacrificial layer, the second sacrificial layer, the third sacrificial layer, the fourth sacrificial layer and the fifth sacrificial layer between the first diaphragm and the second diaphragm are released to form a vacuum gap between the first diaphragm, the second diaphragm, the back pole, the first supporting structure and the second supporting structure, and there is a third gap between the first supporting structure and the first diaphragm, and there is a fourth gap between the second supporting structure and the second diaphragm.

[0041] Optionally, the releasing the first sacrificial layer, the second sacrificial layer, the third sacrificial layer, the fourth sacrificial layer, and the fifth sacrificial layer between the first diaphragm and the second diaphragm to form a vacuum gap between the first diaphragm, the second diaphragm, the back pole, the first supporting structure, and the second supporting structure includes:

[0042] Wet etching the first sacrificial layer, the second sacrificial layer, the third sacrificial layer, the fourth sacrificial layer, and the fifth sacrificial layer between the first diaphragm and the second diaphragm;

[0043] Cleaning and drying to obtain the vacuum gap; wherein the wet etching is performed using hydrofluoric acid or gaseous hydrogen fluoride.

[0044] One technical effect of the present disclosure is:

[0045] The MEMS microphone includes a substrate, a first diaphragm, a backpole, and a second diaphragm. An acoustic cavity is formed on the substrate. The first diaphragm includes a fixed portion and a suspended portion, the fixed portion being disposed on the substrate, and the suspended portion being opposite the acoustic cavity. The backpole is disposed on the substrate, with a first gap formed between the backpole and the first diaphragm. A first supporting structure is disposed on the side of the backpole facing the first diaphragm, extending toward the first diaphragm and opposing the suspended portion. A second supporting structure is disposed on the side of the backpole facing away from the first diaphragm. The second diaphragm is disposed on the backpole, with a second gap formed between the second diaphragm and the backpole, and the second supporting structure extending toward the second diaphragm and opposing the second diaphragm. The first diaphragm and / or the second diaphragm are graphene diaphragms. The excellent elastic modulus and tensile strength of graphene materials can be utilized to reduce the thickness of the first diaphragm and / or the second diaphragm, thereby reducing the overall size of the MEMS microphone and expanding its application range.

[0046] Other features and advantages of the present disclosure will become apparent from the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0048] FIG1 is a schematic structural diagram of a MEMS microphone according to an embodiment of the present disclosure;

[0049] FIG2 is a schematic diagram of a preparation process of a MEMS microphone according to an embodiment of the present disclosure;

[0050] FIG3 is a schematic diagram of a preparation process of a MEMS microphone according to an embodiment of the present disclosure;

[0051] FIG4 is a schematic diagram of a preparation process of another MEMS microphone according to an embodiment of the present disclosure;

[0052] FIG5 is a schematic diagram of a preparation process of another MEMS microphone according to an embodiment of the present disclosure.

[0053] Explanation of the accompanying reference numerals: 1. substrate; 11. acoustic cavity; 2. first diaphragm; 21. fixed portion; 22. suspended portion; 3. first supporting structure; 4. back pole; 5. second supporting structure; 6. second diaphragm. DETAILED DESCRIPTION

[0054] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0055] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0056] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0057] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0058] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0059] This disclosure provides a MEMS (Micro-Electro-Mechanical System) microphone. A MEMS microphone is a microphone manufactured using MEMS technology. Formed using a micro-electromechanical process, a MEMS microphone is compact and highly sensitive. It also exhibits excellent radio frequency interference (RFI) and electromagnetic interference (EMI) suppression capabilities. MEMS microphones are also commonly used in electronic devices such as mid-range and high-end mobile phones.

[0060] As shown in FIG1 , according to one aspect of the present disclosure, a MEMS microphone is provided. The MEMS microphone comprises:

[0061] A substrate 1, wherein a sound cavity 11 is formed on the substrate 1;

[0062] a first diaphragm 2 , the first diaphragm 2 including a fixed portion 21 and a suspended portion 22 , the fixed portion 21 being disposed on the substrate 1 , and the suspended portion 22 being opposite to the acoustic cavity 11 ;

[0063] a backpole 4 disposed on the substrate 1, with a first gap formed between the backpole 4 and the first diaphragm 2; a first supporting structure 3 is disposed on the side of the backpole 4 facing the first diaphragm 2, the first supporting structure 3 extending toward the first diaphragm 2 and opposite to the suspended portion 22; and a second supporting structure 5 is disposed on the side of the backpole 4 away from the first diaphragm 2;

[0064] a second diaphragm 6, wherein the second diaphragm 6 is disposed on the back pole 4, a second gap is formed between the second diaphragm 6 and the back pole 4, the second supporting structure 5 extends toward the second diaphragm 6 and is opposite to the second diaphragm 6, and the first diaphragm 2 and / or the second diaphragm 6 are graphene diaphragms;

[0065] When the MEMS microphone is powered on, the first supporting structure 3 abuts against the suspended portion 22 , and the second supporting structure 5 abuts against the second diaphragm 6 .

[0066] As shown in Figure 1, the present embodiment has an acoustic cavity 11 formed on a substrate 1 for receiving sound signals. A first diaphragm 2 is disposed on the substrate 1. For example, a silicon dioxide layer may be deposited on the substrate 1, and then the first diaphragm 2 is deposited thereon and etched.

[0067] Based on its connection to the base 1, the first diaphragm 2 can be divided into a fixed portion 21 and a suspended portion 22. The fixed portion 21 is mounted on the base 1, while the suspended portion 22 faces the acoustic cavity 11. Specifically, the suspended portion 22 is located in the center and can vibrate, while the fixed portion 21 is located around it and cannot vibrate. Positioning the suspended portion 22 opposite the acoustic cavity 11 allows it to sense sound signals transmitted through the acoustic cavity 11 and vibrate accordingly.

[0068] A back electrode 4 is disposed on the substrate 1 and is disposed opposite the first diaphragm 2. A first gap is formed between the back electrode 4 and the first diaphragm 2, so that the back electrode 4, the first diaphragm 2, and the first gap therebetween collectively constitute a capacitor. The back electrode 4 may be formed using a laminated structure of silicon nitride and polycrystalline silicon, with the silicon nitride forming the structural layer of the back electrode 4 and the polycrystalline silicon forming the conductive layer of the back electrode 4.

[0069] As shown in FIG1 , the embodiment of the present disclosure is provided with a first support structure 3 on the side of the back pole 4 facing the first diaphragm 2. The first support structure 3 can be an annular protrusion structure formed on the back pole 4, such as a continuous annular protrusion or an annular structure formed by multiple discontinuous protrusions. The first support structure 3 can extend toward the first diaphragm 2 and oppose the suspended portion 22. When the MEMS microphone is powered on, the first diaphragm 2 can bend and contact the first support structure 3. The first support structure 3 can be made by depositing materials such as silicon nitride and silicon dioxide.

[0070] A second supporting structure 5 is provided on the side of the back pole 4 away from the first diaphragm 2 . The second supporting structure 5 may be a protruding structure formed on the back pole 4 , such as a continuous annular protrusion or an annular structure formed by multiple discontinuous protrusions.

[0071] Typically, the second support structure 5 and the first support structure 3 are disposed on opposite sides of the backplate 4. This facilitates the arrangement of the second support structure 5 and the first support structure 3, improves the connection reliability between the first support structure 3, the backplate 4, and the second support structure 5 and the first and second diaphragms 2 and 6 on either side, and also improves the structural symmetry and stability of the MEMS microphone. The second support structure 5 can be made of deposited materials such as silicon nitride and silicon dioxide.

[0072] As shown in Figure 1, the second diaphragm 6 is positioned on the backplate 4, with a second gap formed between the second diaphragm 6 and the backplate 4. This allows the backplate 4, the second diaphragm 6, and the second gap therebetween to form a capacitor, thereby forming a differential pressure capacitor structure and improving the overall acoustic performance of the MEMS microphone. A second support structure 5 is provided extending toward the second diaphragm 6 and capable of opposing the second diaphragm 6. When the MEMS microphone is powered on, the second diaphragm 6 can bend and contact the second support structure 5.

[0073] When the MEMS microphone is powered on, the suspended portion 22 can be pushed toward the back pole 4 under the action of electromagnetic force, thereby counteracting the first support structure 3. The second diaphragm 6 can also be pushed toward the back pole 4 under the action of electromagnetic force, thereby counteracting the second support structure 5.

[0074] Alternatively, when the MEMS microphone is formed through chemical vapor deposition, both the first gap and the second gap are vacuum gaps, meaning that the medium between the first diaphragm 2 and the second diaphragm 6 is a vacuum. In this case, under the influence of external atmospheric pressure, the suspended portion 22 can bend and contact the first support structure 3, and the second diaphragm 6 can also bend and contact the second support structure 5.

[0075] When sound pressure acts on the first diaphragm 2, the suspended portion 22 of the first diaphragm 2 will vibrate accordingly, and then drive the second diaphragm 6 to vibrate together through the first supporting structure 3, back pole 4 and second supporting structure 5, thereby forming a dual-diaphragm differential pressure sensing structure with the first diaphragm 2 and the second diaphragm 6.

[0076] Furthermore, the first diaphragm 2 and / or the second diaphragm 6 can be graphene diaphragms. For example, the lower first diaphragm 2 can be a graphene diaphragm, the upper second diaphragm 6 can be a graphene diaphragm, or both the first diaphragm 2 and the second diaphragm 6 can be graphene diaphragms. By leveraging the excellent elastic modulus and tensile strength of graphene materials, the thickness of the first diaphragm 2 and / or the second diaphragm 6 can be reduced, thereby reducing the overall size of the MEMS microphone and expanding its application range. While meeting bandwidth requirements, the mechanical sensitivity of the first diaphragm 2 and the second diaphragm 6 can also be increased, thereby improving the mechanical sensitivity and signal-to-noise ratio of the MEMS microphone, and enhancing the overall acoustic performance of the MEMS microphone.

[0077] According to the actual manufacturing process, a single layer or multi-layer graphene material can also be selected to manufacture the first diaphragm 2 and / or the second diaphragm 6 to improve the structural reliability of the first diaphragm 2 and / or the second diaphragm 6.

[0078] Optionally, the graphene diaphragm includes at least one graphene material layer.

[0079] Specifically, the graphene diaphragm in the disclosed embodiments includes at least one graphene material layer, that is, the graphene diaphragm may include one or more graphene material layers. This allows the graphene material's excellent elastic modulus and tensile strength to be utilized to reduce the thickness of the first diaphragm 2 and / or the second diaphragm 6. This allows the mechanical sensitivity of the first diaphragm 2 and the second diaphragm 6 to be increased while meeting bandwidth requirements, thereby improving the mechanical sensitivity and signal-to-noise ratio of the MEMS microphone, and enhancing the overall acoustic performance of the MEMS microphone. This also facilitates adaptation to different process capabilities and manufacturing requirements.

[0080] For example, a single layer of graphene material can be used to fabricate the first diaphragm 2 and / or the second diaphragm 6, thereby further reducing the thickness of the first diaphragm 2 and / or the second diaphragm 6, thereby facilitating the miniaturization of the MEMS microphone. Alternatively, multiple layers of graphene material can be used to fabricate the first diaphragm 2 and / or the second diaphragm 6, thereby improving the structural reliability of the first diaphragm 2 and / or the second diaphragm 6, thereby improving the structural stability of the MEMS microphone and adapting to more conventional process capabilities.

[0081] Optionally, the graphene diaphragm has a thickness ranging from 0.3 nanometers to 100 nanometers.

[0082] Specifically, the graphene diaphragm in the disclosed embodiments can have a thickness ranging from 0.3 nanometers to 100 nanometers. This means that the thickness of the first diaphragm 2 and / or second diaphragm 6 made of graphene is significantly thinner than that of a conventional polysilicon diaphragm 2 and / or second diaphragm 6. While meeting bandwidth requirements, this can improve the mechanical sensitivity of the first and second diaphragms 2 and 6, thereby enhancing the mechanical sensitivity and signal-to-noise ratio of the MEMS microphone, improving the overall acoustic performance of the MEMS microphone, and facilitating the miniaturization of the MEMS microphone.

[0083] Among them, by adjusting the number of graphene material layers included in the graphene diaphragm, the thickness of the graphene diaphragm can also be adjusted to adapt to different design requirements.

[0084] Optionally, both the first gap and the second gap are vacuum gaps.

[0085] Specifically, in the disclosed embodiment, both the first gap and the second gap are configured as vacuum gaps. For example, when releasing the sacrificial metal layer, a wet etching solution can be used to etch the sacrificial metal layer. After etching, the layer can be cleaned with a cleaning solution (such as deionized water) and dried to obtain a vacuum gap between the first diaphragm 2 and the second diaphragm 6. This vacuum gap can reduce air resistance in the region between the first diaphragm 2 and the second diaphragm 6, thereby improving the signal-to-noise ratio of the MEMS microphone and thereby enhancing the acoustic performance of the MEMS microphone.

[0086] Optionally, the second diaphragm 6 is a graphene diaphragm.

[0087] As shown in Figures 1 to 5 , the disclosed embodiment employs a graphene diaphragm as the second diaphragm 6 . This means that the upper second diaphragm 6 is a graphene diaphragm. This allows the thickness of the first diaphragm 2 and / or the second diaphragm 6 to be reduced by leveraging the excellent elastic modulus and tensile strength of graphene materials. This improves the mechanical sensitivity of the first and second diaphragms 2 and 6 while still meeting bandwidth requirements, thereby enhancing the mechanical sensitivity and signal-to-noise ratio of the MEMS microphone. This also improves the overall acoustic performance of the MEMS microphone and facilitates its miniaturization.

[0088] On the other hand, setting the second diaphragm 6 located at the top as a graphene diaphragm can also utilize the gas isolation property of the graphene material to improve the dustproof ability of the MEMS microphone, improve the working reliability of the MEMS microphone, and also facilitate the formation of a vacuum gap between the first diaphragm 2 and the second diaphragm 6.

[0089] Optionally, the material of the first diaphragm 2 is the same as the material of the second diaphragm 6 .

[0090] As shown in Figures 1 to 3 , the disclosed embodiment employs the same material for the first diaphragm 2 and the second diaphragm 6 , i.e., both the first diaphragm 2 and the second diaphragm 6 are graphene diaphragms. This reduces their thickness, further increasing their mechanical sensitivity while still meeting bandwidth requirements. This improves the mechanical sensitivity and signal-to-noise ratio of the MEMS microphone, enhances its overall acoustic performance, and facilitates its miniaturization.

[0091] On the other hand, setting the first diaphragm 2 and the second diaphragm 6 to be graphene diaphragms, for example, graphene diaphragms can be grown simultaneously on the upper and lower sides of the metal sacrificial layer, which also facilitates the implementation of the process and reduces the difficulty of manufacturing the MEMS microphone. At the same time, it also improves the structural symmetry of the first diaphragm 2 and the second diaphragm 6, which facilitates improving the differential sensing performance of the MEMS microphone.

[0092] Optionally, the material of the first diaphragm 2 is different from the material of the second diaphragm 6 .

[0093] As shown in Figures 1, 4, and 5, the materials of the first diaphragm 2 and the second diaphragm 6 in the disclosed embodiments can be different. Specifically, the first diaphragm 2 can be a conventional polysilicon diaphragm, while the second diaphragm 6 can be a graphene diaphragm. The graphene diaphragm can also be used to reduce the thickness of the second diaphragm 6. This allows the mechanical sensitivity of both the first and second diaphragms 2 and 6 to be increased while still meeting bandwidth requirements. This improves the mechanical sensitivity and signal-to-noise ratio of the MEMS microphone, enhances the overall acoustic performance of the MEMS microphone, and facilitates the miniaturization of the MEMS microphone.

[0094] In addition, keeping the first diaphragm 2 as a conventional polysilicon diaphragm also facilitates adaptation to conventional process capabilities, reduces the processing difficulty of the MEMS microphone, improves the processing efficiency of the MEMS microphone, and facilitates mass production of the MEMS microphone.

[0095] Optionally, the first supporting structure 3 and the second supporting structure 5 are arranged on two sides of the back pole 4 opposite to each other.

[0096] As shown in Figure 1, the embodiment of the present disclosure arranges a first support structure 3 and a second support structure 5 on opposite sides of a backplate 4, which facilitates the arrangement of the second support structure 5 and the first support structure 3, improves the connection reliability between the first support structure 3, the backplate 4, and the second support structure 5 and the first diaphragm 2 and the second diaphragm 6 on either side, and facilitates the vibration of the first diaphragm 2 by driving the second diaphragm 6 to vibrate together through the first support structure 3, the backplate 4, and the second support structure 5. This also improves the structural symmetry and stability of the MEMS microphone. The first support structure 3 and the second support structure 5 can both be made of deposited materials such as silicon nitride and silicon dioxide.

[0097] Optionally, the structure of the second diaphragm 6 is at least the same as the structure of the suspended portion 22 of the first diaphragm 2 .

[0098] Specifically, in the disclosed embodiment, the structure of the second diaphragm 6 is at least identical to that of the suspended portion 22 of the first diaphragm 2. For example, the structure of the second diaphragm 6 is completely identical to that of the suspended portion 22 of the first diaphragm 2. This improves the structural symmetry between the second diaphragm 6 and the first diaphragm 2, thereby enhancing the differential sensing capability of the second diaphragm 6 and the first diaphragm 2. Furthermore, the fact that the structure of the second diaphragm 6 is at least identical to that of the suspended portion 22 of the first diaphragm 2 also enhances the overall aesthetics of the MEMS microphone.

[0099] Optionally, in an embodiment of the present disclosure, when the MEMS microphone is in its initial state, a third gap is provided between the first support structure 3 and the first diaphragm 2, and a fourth gap is provided between the second support structure 5 and the second diaphragm 6. That is, the first support structure 3 and the first diaphragm 2 do not abut against each other, and the second support structure 5 and the second diaphragm 6 do not abut against each other, allowing the first diaphragm 2 and the second diaphragm 6 to sense the external atmospheric pressure and bend accordingly. The third and fourth gaps can be formed after the sacrificial layer between the first diaphragm 2 and the second diaphragm 6 is released.

[0100] Optionally, the MEMS microphone is a differential pressure microphone, which can achieve good differential pressure perception through the first diaphragm 2 and the second diaphragm 6 .

[0101] The present disclosure also provides an electronic device, which includes the above-mentioned MEMS microphone and should have the technical effects possessed by the above-mentioned MEMS microphone.

[0102] In this embodiment, when the electronic device is in operation, the MEMS microphone inside it can receive the user's voice signal and convert the voice signal into an electrical signal. The electronic device may be a mobile phone, a television, a computer, a Bluetooth wireless headset, a smart watch, etc.

[0103] As shown in FIG. 2 and FIG. 3 , the present disclosure further provides a method for manufacturing a MEMS microphone. The first diaphragm 2 and the second diaphragm 6 of the MEMS microphone manufactured by the manufacturing method are both graphene diaphragms.

[0104] Specifically, the preparation method of the MEMS microphone includes:

[0105] Prepare a substrate 1 (not shown);

[0106] The substrate 1 is generally a silicon substrate.

[0107] Depositing a first diaphragm 2 and a first supporting structure 3 on the substrate 1 in sequence;

[0108] As shown in Figure 2(a), silicon is first used as a substrate 1. A layer of silicon dioxide is deposited on the substrate 1, and then selectively masked and etched to form an insulating layer. A first sacrificial layer is then deposited on the insulating layer. This first sacrificial layer is used to form the first diaphragm 2. The material of this first sacrificial layer can be a metal such as nickel, copper, or molybdenum. Silicon nitride, silicon dioxide, or the like is then deposited on this first sacrificial layer and etched to form the first support structure 3.

[0109] Depositing a back electrode 4 and a second supporting structure 5 on the first supporting structure 3 in sequence;

[0110] As shown in Figure 2 (b), a second sacrificial layer is deposited on the first sacrificial layer, and the second sacrificial layer is flush with the first supporting structure 3. The material of the second sacrificial layer can be metals such as nickel, copper, and molybdenum. Afterwards, as shown in Figure 2 (c), a stacked structure of silicon nitride and polysilicon is deposited, and the back electrode 4 is obtained by etching. The back electrode 4 can also be made of other conventional materials. Afterwards, as shown in Figure 2 (d), a third sacrificial layer is deposited, and the third sacrificial layer is flush with the back electrode 4. The material of the third sacrificial layer can be metals such as nickel, copper, and molybdenum. Afterwards, silicon nitride, silicon dioxide, etc. are deposited on the third sacrificial layer, and the second supporting structure 5 is obtained after etching.

[0111] A second diaphragm 6 is deposited on the second supporting structure 5 . The first diaphragm 2 and the second diaphragm 6 are connected to each other, and the first diaphragm 2 and the second diaphragm 6 are graphene diaphragms.

[0112] As shown in Figure 2(e), a fourth sacrificial layer is deposited and aligned with the second support structure 5. The fourth sacrificial layer can be made of a metal such as nickel, copper, or molybdenum. Subsequently, as shown in Figure 2(f), a fifth sacrificial layer is deposited on the fourth sacrificial layer. This fifth sacrificial layer is used to form the second diaphragm 6. The fifth sacrificial layer can be made of a metal such as nickel, copper, or molybdenum.

[0113] Next, as shown in Figure 2(g), graphene is grown below the first sacrificial layer and above the fifth sacrificial layer to form the first diaphragm 2 and the second diaphragm 6. Next, as shown in Figure 2(h), chromium or titanium tungsten is deposited to form the connecting metal. Next, as shown in Figure 3(i), silicon nitride, silicon dioxide, etc. are deposited and passivation treatment is performed.

[0114] Afterwards, as shown in (j) in Figure 3, the first to fifth sacrificial layers are partially released. Afterwards, as shown in (k) in Figure 3, the lower electrode is made. Afterwards, as shown in (l) in Figure 3, solder joints are made, and solder joints are provided on at least the first diaphragm 2, the second diaphragm 6 and the back pole 4. Afterwards, as shown in (m) in Figure 3, the substrate 1 is released, and the acoustic cavity 11 is formed. Afterwards, as shown in (n) in Figure 3, the connecting metal is partially released to expose the second diaphragm 6. Afterwards, as shown in (o) in Figure 3, the insulating layer is partially released to expose the first diaphragm 2. Finally, as shown in (p) in Figure 3, the remaining sacrificial layer between the first diaphragm 2 and the second diaphragm 6 is released to connect the first diaphragm 2 and the second diaphragm 6 and form a vacuum gap.

[0115] As shown in Figures 4 and 5, the present disclosure also provides another method for preparing a MEMS microphone. The first diaphragm 2 of the MEMS microphone prepared by this method is a polysilicon diaphragm, and the second diaphragm 6 is a graphene diaphragm. The preparation method of this MEMS microphone is basically similar to the above method, except that:

[0116] First, a layer of polysilicon is deposited on the insulating layer to form the first diaphragm 2, followed by the first sacrificial layer. When graphene is subsequently grown, it is grown only on top of the fifth sacrificial layer to form the second diaphragm 6, resulting in the MEMS microphone structure shown in Figure 5 (p).

[0117] Optionally, the step of sequentially depositing a first diaphragm 2 and a first supporting structure 3 on the substrate 1; sequentially depositing a back electrode 4 and a second supporting structure 5 on the first supporting structure 3; and depositing a second diaphragm 6 on the second supporting structure 5 comprises:

[0118] A first diaphragm 2 is deposited on the substrate 1, wherein the first diaphragm 2 is a polysilicon layer or a first sacrificial layer; Figures 2 and 3 illustrate that the first diaphragm 2 is formed on the first sacrificial layer, and Figures 4 and 5 illustrate that the first diaphragm 2 is a polysilicon layer;

[0119] Depositing a first supporting structure 3 on the first diaphragm 2, as shown in FIG2(a) and FIG4(a);

[0120] Depositing a second sacrificial layer, wherein the second sacrificial layer is flush with the first supporting structure 3, as shown in FIG. 2(b) and FIG. 4(b);

[0121] Depositing a back electrode 4 on the second sacrificial layer, as shown in FIG. 2( c ) and FIG. 4( c );

[0122] Depositing a third sacrificial layer, wherein the third sacrificial layer is flush with the back electrode 4;

[0123] Depositing a second support structure 5 on the third sacrificial layer, as shown in FIG. 2( d ) and FIG. 4( d );

[0124] Depositing a fourth sacrificial layer, wherein the fourth sacrificial layer is flush with the second supporting structure 5 , as shown in FIG. 2 ( e ) and FIG. 4 ( e );

[0125] Depositing a fifth sacrificial layer, as shown in FIG2(f) and FIG4(f);

[0126] Growing graphene, growing graphene on the fifth sacrificial layer, or growing graphene both below the first sacrificial layer and above the fifth sacrificial layer, as shown in FIG. 2( g ) and FIG. 4( g );

[0127] Release the sacrificial layer and obtain the MEMS microphone.

[0128] Optionally, releasing the sacrificial layer and obtaining the MEMS microphone includes:

[0129] As shown in (p) in Figure 3 and (p) in Figure 5, the first sacrificial layer, the second sacrificial layer, the third sacrificial layer, the fourth sacrificial layer and the fifth sacrificial layer between the first diaphragm 2 and the second diaphragm 6 are released to form a vacuum gap between the first diaphragm 2, the second diaphragm 6, the back pole 4, the first supporting structure 3 and the second supporting structure 5, and there is a third gap between the first supporting structure 3 and the first diaphragm 2, and a fourth gap between the second supporting structure 5 and the second diaphragm 6.

[0130] Optionally, the releasing of the first sacrificial layer, the second sacrificial layer, the third sacrificial layer, the fourth sacrificial layer, and the fifth sacrificial layer between the first diaphragm 2 and the second diaphragm 6 to form a vacuum gap between the first diaphragm 2, the second diaphragm 6, the back pole 4, the first supporting structure 3, and the second supporting structure 5 includes:

[0131] Wet etching the first sacrificial layer, the second sacrificial layer, the third sacrificial layer, the fourth sacrificial layer, and the fifth sacrificial layer between the first diaphragm 2 and the second diaphragm 6;

[0132] Among them, based on the fact that the second diaphragm 6 is made of graphene material, the characteristics of the graphene material can be utilized to achieve pore-free wet chemical etching, so that a vacuum gap can be conveniently formed between the first diaphragm 2, the second diaphragm 6, the back pole 4, the first support structure 3 and the second support structure 5 while releasing the sacrificial layer, thereby improving the sensing sensitivity of the MEMS microphone obtained by this preparation method.

[0133] Cleaning and drying to obtain the vacuum gap; wherein the wet etching can be performed using hydrofluoric acid or gaseous hydrogen fluoride.

[0134] The above embodiments focus on the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. Considering the simplicity of the text, they will not be repeated here.

[0135] Although some specific embodiments of the present disclosure have been described in detail by way of examples, those skilled in the art will appreciate that the above examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Those skilled in the art will appreciate that modifications may be made to the above embodiments without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A MEMS microphone, include: A substrate (1), wherein a sound cavity (11) is formed on the substrate (1); A first diaphragm (2), the first diaphragm (2) comprising a fixed portion (21) and a suspended portion (22), the fixed portion (21) being arranged on the substrate (1), and the suspended portion (22) being opposite to the acoustic cavity (11); a back pole (4), the back pole (4) being arranged on the substrate (1), a first gap being formed between the back pole (4) and the first diaphragm (2), a first supporting structure (3) being arranged on a side of the back pole (4) facing the first diaphragm (2), the first supporting structure (3) extending towards the first diaphragm (2) and opposite to the suspended portion (22), and a second supporting structure (5) being arranged on a side of the back pole (4) away from the first diaphragm (2); a second diaphragm (6), wherein the second diaphragm (6) is arranged on the back pole (4), a second gap is formed between the second diaphragm (6) and the back pole (4), the second supporting structure (5) extends toward the second diaphragm (6) and is opposite to the second diaphragm (6), and the first diaphragm (2) and / or the second diaphragm (6) are graphene diaphragms; When the MEMS microphone is powered on, the first supporting structure (3) abuts against the suspended portion (22), and the second supporting structure (5) abuts against the second diaphragm (6).

2. A MEMS microphone according to claim 1, in, The graphene diaphragm includes at least one graphene material layer.

3. A MEMS microphone according to claim 1 or 2, in, The thickness of the graphene diaphragm ranges from 0.3 nanometers to 100 nanometers.

4. A MEMS microphone according to any one of claims 1 to 3, in, The first gap and the second gap are both vacuum gaps.

5. A MEMS microphone according to any one of claims 1 to 4, in, The second diaphragm (6) is a graphene diaphragm.

6. A MEMS microphone according to any one of claims 1 to 5, in, The material of the first diaphragm (2) is the same as the material of the second diaphragm (6).

7. A MEMS microphone according to any one of claims 1 to 6, in, The material of the first diaphragm (2) is different from the material of the second diaphragm (6).

8. A MEMS microphone according to any one of claims 1 to 7, in, The first supporting structure (3) and the second supporting structure (5) are arranged oppositely on two sides of the back pole (4).

9. A MEMS microphone according to any one of claims 1 to 8, in, A third gap is provided between the first supporting structure (3) and the first diaphragm (2), and a fourth gap is provided between the second supporting structure (5) and the second diaphragm (6).

10. A MEMS microphone according to any one of claims 1 to 9, in, The MEMS microphone is a differential pressure microphone.

11. An electronic device comprising the MEMS microphone according to any one of claims 1 to 10.

12. A method for preparing a MEMS microphone, include: Making a base; Depositing a first diaphragm and a first supporting structure on the substrate in sequence; Depositing a back electrode and a second supporting structure sequentially on the first supporting structure; A second diaphragm is deposited on the second supporting structure, the first diaphragm is connected to the second diaphragm, and the first diaphragm and / or the second diaphragm is a graphene diaphragm.

13. The method for preparing a MEMS microphone according to claim 12, in, Depositing a first diaphragm and a first supporting structure on the substrate in sequence; Depositing a back electrode and a second supporting structure sequentially on the first supporting structure; Depositing a second diaphragm on the second supporting structure comprises: Depositing a first diaphragm on the substrate, wherein the first diaphragm is a polysilicon layer or is formed on a first sacrificial layer; depositing a first support structure on the first diaphragm; depositing a second sacrificial layer, wherein the second sacrificial layer is flush with the first support structure; depositing a back electrode on the second sacrificial layer; Depositing a third sacrificial layer, wherein the third sacrificial layer is flush with the back electrode; depositing a second support structure on the third sacrificial layer; depositing a fourth sacrificial layer, wherein the fourth sacrificial layer is flush with the second support structure; depositing a fifth sacrificial layer; Growing graphene, growing graphene on the fifth sacrificial layer, or growing graphene both below the first sacrificial layer and above the fifth sacrificial layer; Release the sacrificial layer and obtain the MEMS microphone.

14. A method for preparing a MEMS microphone according to claim 12 or 13, in, The method of releasing the sacrificial layer and obtaining the MEMS microphone comprises: The first sacrificial layer, the second sacrificial layer, the third sacrificial layer, the fourth sacrificial layer and the fifth sacrificial layer between the first diaphragm and the second diaphragm are released to form a vacuum gap between the first diaphragm, the second diaphragm, the back pole, the first supporting structure and the second supporting structure, and a third gap is formed between the first supporting structure and the first diaphragm, and a fourth gap is formed between the second supporting structure and the second diaphragm.

15. A method for preparing a MEMS microphone according to any one of claims 12 to 14, in, The step of releasing the first sacrificial layer, the second sacrificial layer, the third sacrificial layer, the fourth sacrificial layer and the fifth sacrificial layer between the first diaphragm and the second diaphragm to form a vacuum gap between the first diaphragm, the second diaphragm, the back pole, the first supporting structure and the second supporting structure comprises: Wet-etching the first sacrificial layer, the second sacrificial layer, the third sacrificial layer, the fourth sacrificial layer and the fifth sacrificial layer between the first diaphragm and the second diaphragm; Cleaning and drying to obtain the vacuum gap; wherein the wet etching is performed using hydrofluoric acid or gas phase hydrogen fluoride.

Images