Method for preparing micro-electro-mechanic-system microphone

Abstract

Provided in the present invention is a method for preparing a micro-electro-mechanic-system microphone, the method comprising the following steps: selecting a substrate, and preparing a first baffle structure on a first surface of the substrate; preparing a diaphragm structure on the side of the first baffle structure facing away from the substrate, the orthographic projection of the periphery of the diaphragm structure on the first baffle falling on the first baffle; preparing a second baffle structure on the side of the diaphragm structure facing away from the first baffle and at a distance from the first baffle, the second baffle structure being connected to the first baffle structure, and at least part of the orthographic projection of the second baffle structure on the diaphragm structure falling on the periphery of the diaphragm structure; preparing a backplate structure on the side of the second baffle structure facing away from the diaphragm structure and at a distance from the second baffle structure, the backplate structure comprising several acoustic through-holes; and etching a second surface of the substrate opposite the first surface, so as to form a back cavity structure. Compared with the related art, the method for preparing a micro-electro-mechanic-system microphone of the present invention aims to improve the degree of freedom of the diaphragm to improve the sensitivity of a micro-electro-mechanic-system microphone, and also improve the structural strength of the diaphragm structure.

Description

Preparation method of micro-electromechanical microphone Technical Field

[0001] The present invention relates to the technical field of microphones, and in particular to a method for preparing a micro-electromechanical microphone. Background Art

[0002] With the development of wireless communications, users have higher and higher requirements for the call quality of mobile phones. The microphone is the voice pickup device of the mobile phone, and its design directly affects the call quality of the mobile phone.

[0003] Micro-Electro-Mechanic System (MEMS) technology has gained industry favor due to its miniaturization, ease of integration, high performance, and low cost. MEMS microphones are widely used in current mobile phones. Common MEMS microphones are capacitive, consisting of a diaphragm and a backplate, which together form the MEMS acoustic sensor capacitor. In addition to low-noise design, high sensitivity is also a key consideration in high-performance MEMS microphones. Existing MEMS microphones use a four-cantilever beam design, which allows the diaphragm to have a large degree of freedom, thereby achieving high sensitivity.

[0004] However, in reliability tests of the aforementioned MEMS microphone design, the narrow cantilever beam becomes a weak point for the diaphragm to break when it collides with the substrate or backplate. Therefore, it is necessary to provide a new fabrication method for microelectromechanical microphones that increases the diaphragm's degree of freedom while also enhancing its structural strength. Summary of the Invention

[0005] The object of the present invention is to overcome the above technical problems and provide a method for preparing a micro-electromechanical microphone that can improve the degree of freedom of the diaphragm while improving the structural strength of the diaphragm.

[0006] To achieve the above object, an embodiment of the present invention provides a method for preparing a micro-electromechanical microphone, comprising the following steps:

[0007] selecting a substrate and depositing a first oxide layer on a first surface of the substrate;

[0008] patterning a first oxide layer, wherein the first oxide layer includes a plurality of first connecting through holes;

[0009] Depositing a first silicon nitride layer on the surface of the first oxide layer until the first connecting through hole is filled, and patterning the first silicon nitride layer to form a first baffle structure;

[0010] Depositing a second oxide layer on the surface of the first baffle structure and patterning the second oxide layer, wherein the second oxide layer includes a second connecting through hole;

[0011] Depositing a first polysilicon layer on the surface of the second oxide layer until the second connecting through hole is filled, patterning the first polysilicon layer to form a diaphragm structure, wherein the orthographic projection of the periphery of the diaphragm structure onto the first baffle falls on the first baffle;

[0012] Depositing a third oxide layer on the surface of the diaphragm structure and patterning the layer to expose at least a portion of the first baffle;

[0013] Depositing a second silicon nitride layer on the surface of the third oxide layer, and patterning the second silicon nitride layer to form a second baffle structure, wherein the second baffle structure is connected to the first baffle structure, and an orthographic projection of the second baffle structure onto the diaphragm structure at least partially falls on a periphery of the diaphragm structure;

[0014] Depositing a fourth oxide layer on the surface of the second baffle structure, depositing a backplane material layer on the surface of the fourth oxide layer, and patterning the backplane material layer to form a backplane structure, wherein the backplane structure includes a plurality of acoustic through holes;

[0015] etching the substrate from the back to form a back cavity structure corresponding to the middle main body area of ​​the back plate structure;

[0016] The third oxide layer and the fourth oxide layer are removed through the acoustic through hole, and the first oxide layer and the second oxide layer above the back cavity structure are removed through the back cavity structure.

[0017] Furthermore, patterning the first oxide layer includes etching a first ring-shaped connecting through hole at a position close to an edge of the first oxide layer and along an edge of the first oxide layer.

[0018] Furthermore, there are a plurality of first connection through holes, and the plurality of first connection through holes are sequentially spaced apart from each other in a direction from a central portion to an edge portion of the first oxide layer.

[0019] Furthermore, patterning the second oxide layer includes etching a second connecting through hole at a position close to an edge of the second oxide layer.

[0020] Furthermore, the portion of the first polysilicon layer that fills the second connecting through hole serves as an extraction electrode of the diaphragm structure.

[0021] Furthermore, depositing the first oxide layer includes sequentially depositing a first sub-oxide layer and a second sub-oxide layer, and the deposition thickness of the second sub-oxide layer is greater than that of the first sub-oxide layer.

[0022] Furthermore, a ratio of the thickness of the second sub-oxide layer to the thickness of the first sub-oxide layer is 2 to 5.

[0023] Furthermore, forming the back cavity structure includes thinning and etching the substrate from the second surface of the substrate.

[0024] Furthermore, depositing the back plate material layer includes sequentially depositing a third silicon nitride layer and a second polysilicon layer.

[0025] Compared with the related art, the preparation method of the micro-electromechanical microphone provided by the present invention respectively sets a first baffle structure and a second baffle structure at both ends of the diaphragm structure along the vibration direction, so as to utilize the first baffle structure and the second baffle structure to limit the displacement of the diaphragm structure in the vibration direction, thereby reducing the possibility of the diaphragm structure reaching the fracture stress, thereby improving the structural strength of the diaphragm structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which:

[0027] FIG1 is a schematic structural diagram of a micro-electromechanical microphone according to an embodiment of the present invention;

[0028] FIG2 is a flow chart of a method for manufacturing a micro-electro-mechanical microphone according to one embodiment of the present invention;

[0029] 3a to 3o are schematic diagrams of a fabrication process of a MEMS microphone according to one embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Referring to FIG. 1 , a micro-electro-mechanical microphone 100 fabricated using the fabrication method of the present invention includes a substrate 10 and a capacitor system 20 disposed on the substrate 10 and insulated from and connected to the substrate 10 .

[0032] The substrate 10 is preferably made of a semiconductor material, such as silicon, and has a back cavity 101, a first surface 10A, and a second surface 10B opposite the first surface 10A. Accordingly, in the following description of the embodiments of the present invention, the first surface 10A represents the upper surface direction, and the second surface 10B represents the lower surface direction. The back cavity 101 can be formed by a bulk silicon process or dry etching.

[0033] The capacitor system 20 includes a diaphragm 21, a backplate 22 opposite the diaphragm 21, and a first baffle 23 and a second baffle 24 disposed on the lower and upper sides of the diaphragm 21, respectively. The diaphragm 21 includes an electrode lead-out portion 103, through which the diaphragm 21 is connected to the first baffle 23. The remaining portion of the diaphragm 21 is spaced apart from the first baffle 23 in the vibration direction X. The diaphragm 21 is also spaced apart from the second baffle 24 in the vibration direction X. As a result, the diaphragm 21 is connected to the first baffle 23 only at one point, through the electrode lead-out portion 103. The remaining portion of the diaphragm 21 is not connected to any other components in the vibration direction X. This improves the release of the diaphragm 21, provides the diaphragm 21 with a greater degree of freedom in the vibration direction X, and thereby enhances the sensitivity of the micro-electromechanical microphone 100.

[0034] In these embodiments of the present application, the electrode lead portion 103 is a lead electrode of the diaphragm 21 .

[0035] At the same time, the projections of the peripheral portion of the diaphragm 21 and the first baffle 23, as well as the projections of the peripheral portion of the diaphragm 21 and the second baffle 24 in the vibration direction X overlap, so that the first baffle 23 and the second baffle 24 can respectively limit the diaphragm 21 when the diaphragm 21 vibrates, thereby reducing the possibility of the diaphragm 21 being displaced to the point of breaking stress, thereby reducing the risk of the diaphragm 21 breaking due to excessive displacement during vibration, thereby improving the structural strength of the diaphragm 21.

[0036] When the MEMS microphone 100 is powered on, the diaphragm 21 and the backplate 22 are charged with opposite polarities, thereby forming a capacitor. When the diaphragm 21 vibrates under the action of sound waves, the distance between the backplate 22 and the diaphragm 21 changes, causing the capacitance of the capacitor system 20 to change, thereby converting the sound wave signal into an electrical signal, thereby realizing the corresponding function of the MEMS microphone 100.

[0037] In these embodiments of the present invention, the cross section of the diaphragm 21 perpendicular to the vibration direction X may be, but is not limited to, rectangular or circular.

[0038] The first baffle 23 and the second baffle 24 may be made of or include a semiconductor material such as silicon, for example, germanium, silicon germanium, silicon carbide, gallium nitride, indium, indium gallium nitride, indium gallium arsenide, indium gallium zinc oxide, or other elemental and / or compound semiconductors (e.g., III-V compound semiconductors such as gallium arsenide or indium phosphide, or II-VI compound semiconductors, or ternary compound semiconductors, or quaternary compound semiconductors). They may also be made of or include at least one of the following: a metal, a dielectric material, a piezoelectric material, a piezoresistive material, and a ferroelectric material. They may also be made of a dielectric material such as silicon nitride.

[0039] In some embodiments of the present invention, the first baffle 23 , the second baffle 24 and the back plate 22 may be integrally formed.

[0040] Please refer to FIG. 3 a to FIG. 3 o , which are flow charts of an embodiment of a method for manufacturing a MEMS microphone provided by the present invention. The method is used to manufacture the MEMS microphone 100 shown in FIG. 1 or FIG. 2 , and specifically includes the following steps.

[0041] Step S1, selecting a substrate 10, and preparing a first baffle 23 structure on the first surface 10A of the substrate 10, including the following sub-steps:

[0042] S11 , selecting a substrate 10 , and depositing a first oxide layer 231 on the first surface 10A of the substrate 10 , as shown in FIG. 3 a .

[0043] The substrate 10 is, for example, a semiconductor silicon substrate, or may be a substrate of other semiconductor materials, such as germanium, silicon germanium, silicon carbide, gallium nitride, indium, indium gallium nitride, indium gallium arsenide, indium gallium zinc oxide, or other element and / or compound semiconductors (e.g., III-V compound conductors such as gallium arsenide or indium phosphide), germanium, or gallium nitride.

[0044] The first oxide layer 231 is, for example, silicon dioxide, and can be formed by conventional processes such as thermal oxidation and vapor deposition.

[0045] In some embodiments, depositing the first oxide layer 231 may include sequentially depositing a first sub-oxide layer 2311 and a second sub-oxide layer 2312 , wherein a deposition thickness of the second sub-oxide layer 2312 is greater than a deposition thickness of the first sub-oxide layer 2311 .

[0046] For example, in some embodiments, the ratio of the thickness of the second sub-oxide layer 2312 to the thickness of the first sub-oxide layer 2311 can be set to 2 to 5. For example, the thickness of the second sub-oxide layer 2312 can be set to 3 times or 4 times the thickness of the first sub-oxide layer 2311.

[0047] S12, patterning the first oxide layer 231 so that the first oxide layer 231 includes a plurality of first connecting through holes 104, as shown in FIG. 3b.

[0048] In this step, the first connecting vias 104 expose a portion of the first surface 10A of the substrate 10 from the first oxide layer 231 , so as to contact the first silicon nitride layer 232 during a subsequent deposition process to form a connecting conductive structure.

[0049] In some embodiments of the present invention, a first connecting through hole 104 having a ring shape can be etched along the edge of the first oxide layer 231 near the edge of the first oxide layer 231. The edge of the first oxide layer 231 refers to the edge on a plane parallel to the first surface 10A of the substrate 10; and the ring shape of the first connecting through hole 104 refers to the ring shape of the cross section of the first connecting through hole 104 parallel to the first surface 10A of the substrate 10, which is similar to the outer contour of the first oxide layer 231.

[0050] Preferably, in some embodiments, a plurality of first connecting through holes 104 may be provided, and the plurality of first connecting through holes 104 may be spaced apart from each other along the center portion toward the edge portion of the first oxide layer 231. This increases the contact area between the subsequently deposited first silicon nitride layer 232 and the substrate 10, thereby improving the structural consistency between the first silicon nitride layer 232 and the substrate 10.

[0051] S13 , depositing a first silicon nitride layer 232 on the surface of the first oxide layer 231 until the first connecting through hole 104 is filled, and patterning the first silicon nitride layer 232 to form a first baffle 23 structure, as shown in FIG. 3 d .

[0052] The first silicon nitride layer 232 is patterned so as to be processed into a first baffle 23 structure in a ring shape.

[0053] Step S2, preparing the diaphragm 21 structure on the side of the first baffle 23 structure facing away from the substrate 10, includes the following sub-steps:

[0054] S21 , depositing a second oxide layer 211 on the surface of the first baffle 23 structure, and patterning the second oxide layer 211 , wherein the second oxide layer 211 includes a second connecting through hole 2111 , as shown in FIG. 3 e .

[0055] In some embodiments, patterning the second oxide layer 211 may include etching a second connecting through hole 2111 near an edge of the second oxide layer 211 .

[0056] S22, depositing a first polysilicon layer 212 on the surface of the second oxide layer 211 until the second connecting through-hole 2111 is completely filled, and patterning the first polysilicon layer 212 to form a diaphragm 21 structure. The orthographic projection of the periphery of the diaphragm 21 structure onto the first baffle 23 falls on the first baffle 23, as shown in Figures 3f to 3g.

[0057] In these embodiments of the present invention, the portion of the first polysilicon layer 212 that fills the second connecting through-hole 2111 is the subsequent connection position between the diaphragm 21 and the first baffle 23. In some embodiments, the second connecting through-hole 2111 can be set at a certain position along the periphery of the second oxide layer 211, thereby reducing the number of connection points between the diaphragm 21 and other components, thereby releasing the diaphragm 21 more, allowing the diaphragm 21 to obtain more degrees of freedom in the vibration direction, and thereby improving the sensitivity of the micro-electromechanical microphone 100.

[0058] For example, in some embodiments, the portion of the diaphragm 21 structure corresponding to the second connecting through hole 2111 may be set as the electrode lead-out structure of the diaphragm 21 to simultaneously achieve connection and electrical conduction of the diaphragm 21 .

[0059] At the same time, the positive projection of the periphery of the diaphragm 21 structure onto the first baffle 23 falls on the first baffle 23. The first baffle 23 can be used to provide a limit for the diaphragm 21 on one side of the vibration direction X of the diaphragm 21, so that the diaphragm 21 will not undergo excessive displacement on this side, thereby reducing the possibility of the diaphragm 21 structure reaching fracture stress, thereby improving the structural strength of the diaphragm 21 structure.

[0060] Step S3, preparing a second baffle 24 structure on a side of the diaphragm 21 structure away from the first baffle 23, includes the following sub-steps:

[0061] S31 , depositing a third oxide layer 241 on the surface of the diaphragm 21 and patterning the layer to expose at least a portion of the first baffle 23 , as shown in FIG3 h .

[0062] S32, depositing a second silicon nitride layer 242 on the surface of the third oxide layer 241, and patterning the second silicon nitride layer 242 to form a second baffle 24 structure, wherein the second baffle 24 structure is connected to the first baffle 23 structure, and the orthographic projection of the second baffle 24 structure onto the diaphragm 21 structure at least partially falls on the periphery of the diaphragm 21 structure, as shown in Figure 3i.

[0063] The second baffle 24 is connected to the first baffle 23 , meaning that when depositing the second silicon nitride layer 242 , the second silicon nitride layer 242 can be in contact with the portion of the first baffle 23 exposed in step S31 . Furthermore, when the second silicon nitride layer 242 is subsequently patterned, the portion of the second silicon nitride layer 242 in contact with the first baffle 23 is retained, so that the first baffle 23 and the second baffle 24 form an integrated structure. This improves the structural consistency of the MEMS microphone 100 and enhances its structural reliability.

[0064] The positive projection of the second baffle 24 structure onto the diaphragm 21 structure at least partially falls on the periphery of the diaphragm 21 structure, which means that the structure of the second baffle 24 is similar to that of the first baffle 23, both of which are annular structures corresponding to the periphery of the diaphragm 21. The second baffle 24 is used to provide a limit for the diaphragm 21 on the other side of the diaphragm 21 along the vibration direction X, thereby reducing the excessive displacement of the diaphragm 21 on the side close to the second baffle 24 during the vibration process, thereby reducing the possibility of the diaphragm 21 structure reaching the fracture stress, thereby improving the structural strength of the diaphragm 21 structure.

[0065] Step S4, preparing a back plate 22 structure on a side of the second baffle 24 structure away from the diaphragm 21 structure, wherein the back plate 22 structure includes a plurality of acoustic through holes 102, includes the following sub-steps:

[0066] S41, depositing a fourth oxide layer 221 on the surface of the second baffle 24 structure, depositing a backplane material layer 222 on the surface of the fourth oxide layer 221, and patterning the backplane material layer 222 to form a backplane 22 structure, the backplane 22 structure including a plurality of acoustic through holes 102, as shown in Figures 3j to 3m.

[0067] Depositing the back plate material layer 222 includes sequentially depositing a third silicon nitride layer 2221 and a second polysilicon layer 2222 .

[0068] The acoustic through hole 102 penetrates the third silicon nitride layer 2221 and the second polysilicon layer 2222 along the vibration direction X of the diaphragm 21 .

[0069] Step S5, etching the second surface 10B of the substrate 10 opposite to the first surface 10A to form a back cavity 101 structure, includes the following sub-steps:

[0070] S51, etching the substrate 10 from the back to form a back cavity 101 structure corresponding to the middle main body area of ​​the back plate 22 structure, as shown in FIG3n.

[0071] For example, in some embodiments, the second surface 10B of the substrate 10 may be thinned by a grinding process, and then the second surface 10B of the substrate 10 may be patterned and etched to form the back cavity 101 region, with the etching stopping at the first oxide layer 231 .

[0072] S52 , removing the third oxide layer 241 and the fourth oxide layer 221 through the acoustic through hole 102 , and removing the first oxide layer 231 and the second oxide layer 211 above the back cavity 101 structure through the back cavity 101 structure, as shown in FIG. 3 o .

[0073] For example, the first oxide layer 231 , the second oxide layer 211 , the third oxide layer 241 and the fourth oxide layer 221 may be removed by using a BOE solution or HF vapor etching technique.

[0074] The above description is only an embodiment of the present invention. It should be pointed out that those skilled in the art can make improvements without departing from the creative concept of the present invention, but these improvements all fall within the scope of protection of the present invention.

Claims

1. A method for manufacturing a microelectromechanical microphone, characterized in that, it comprises the following steps: Select a substrate, and deposit a first oxide layer on the first surface of the substrate; Pattern the first oxide layer, and the first oxide layer includes a plurality of first connection through-holes; Deposit a first silicon nitride layer on the surface of the first oxide layer until the first connection through-holes are filled, and pattern the first silicon nitride layer to form a first baffle structure; Deposit a second oxide layer on the surface of the first baffle structure, and pattern the second oxide layer, and the second oxide layer includes second connection through-holes; Deposit a first polysilicon layer on the surface of the second oxide layer until the second connection through-holes are filled, and pattern the first polysilicon layer to form a diaphragm structure, and the orthographic projection of the periphery of the diaphragm structure onto the first baffle falls on the first baffle; Deposit a third oxide layer on the surface of the diaphragm structure and pattern it to expose at least part of the first baffle; Deposit a second silicon nitride layer on the surface of the third oxide layer, and pattern the second silicon nitride layer to form a second baffle structure, the second baffle structure is connected to the first baffle structure, and the orthographic projection of the second baffle structure onto the diaphragm structure at least partially falls on the periphery of the diaphragm structure; Deposit a fourth oxide layer on the surface of the second baffle structure, deposit a backplate material layer on the surface of the fourth oxide layer, and pattern the backplate material layer to form a backplate structure, and the backplate structure includes a plurality of acoustic through-holes; Etch the back of the substrate to form a back cavity structure corresponding to the middle main area of the backplate structure; Remove the third oxide layer and the fourth oxide layer through the acoustic through-holes, and remove the first oxide layer and the second oxide layer above the back cavity structure through the back cavity structure.

2. The method for manufacturing a microelectromechanical microphone according to claim 1, characterized in that, The patterning of the first oxide layer includes etching a ring-shaped first connection through-hole along the edge of the first oxide layer at a position close to the edge of the first oxide layer.

3. The method for manufacturing a microelectromechanical microphone according to claim 2, characterized in that, The number of the first connection through-holes is multiple, and the multiple first connection through-holes are sequentially arranged at intervals in the direction from the central part to the edge part of the first oxide layer.

4. The method for manufacturing a microelectromechanical microphone according to claim 1, characterized in that, The patterning of the second oxide layer includes etching the second connection through-hole at a position close to the edge of the second oxide layer.

5. The method for manufacturing a microelectromechanical microphone according to claim 4, characterized in that, The part of the first polysilicon layer that fills the second connection through-hole is the lead electrode of the diaphragm structure.

6. The method for manufacturing a microelectromechanical microphone according to claim 1, characterized in that, The deposition of the first oxide layer includes sequentially depositing a first sub-oxide layer and a second sub-oxide layer, and the deposition thickness of the second sub-oxide layer is greater than the deposition thickness of the first sub-oxide layer.

7. The method for manufacturing a microelectromechanical microphone according to claim 6, characterized in that, The ratio of the thickness of the second sub-oxide layer to the thickness of the first sub-oxide layer is 2 to 5.

8. The method for manufacturing a MEMS microphone according to claim 1, wherein, forming the back cavity structure includes thinning and etching the substrate from the second surface of the substrate.

9. The method for manufacturing a MEMS microphone according to claim 1, wherein, depositing the backplane material layer includes sequentially depositing a third silicon nitride layer and a second polysilicon layer.

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