CN117376796B - Preparation method of microelectromechanical microphone - Google Patents

Abstract

The invention provides a method for preparing a microelectromechanical microphone, which includes the following steps: selecting a substrate, preparing a first baffle structure on the 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 to the first baffle falls on the first baffle; a second baffle structure is prepared at intervals on the side of the diaphragm structure away from the first baffle, and the second baffle structure is in contact with the first baffle. The plate structures are connected, and the orthographic projection of the second baffle structure to the diaphragm structure at least partially falls on the periphery of the diaphragm structure; a backplate structure is prepared at intervals on the side of the second baffle structure away from the diaphragm structure, and the backplate structure includes A plurality of acoustic through holes; etching the second surface of the substrate opposite to the first surface to form a back cavity structure. Compared with related technologies, the preparation method of the microelectromechanical microphone of the present invention aims to increase the degree of freedom of the diaphragm to improve the sensitivity of the microelectromechanical microphone and at the same time improve the structural strength of the diaphragm structure.

Description

Preparation method of microelectromechanical microphone

Technical field

The present invention relates to the field of microphone technology, and in particular, to a method for preparing a microelectromechanical microphone.

Background technique

With the development of wireless communications, users have higher and higher requirements for the call quality of mobile phones. As the voice pickup device of mobile phones, the design of the microphone directly affects the call quality of mobile phones.

Micro-Electro-Mechanic System (MEMS) technology is favored by the industry due to its miniaturization, easy integration, high performance, and low cost. MEMS microphones are widely used in current mobile phones; common MEMS microphones are capacitive, which include a diaphragm and a backplate, both of which constitute a MEMS sound sensing capacitor. In addition to low-noise design, high-performance MEMS microphones also require high-sensitivity MEMS microphone design. important factors to consider. In the existing technology, MEMS microphones adopt a design of four cantilever beams, which allows the diaphragm to obtain a greater degree of freedom and thereby obtain high sensitivity.

However, in the reliability test of the aforementioned MEMS microphone design, when the diaphragm collides with the substrate or back plate, the narrow cantilever beam becomes the fracture weak point of the diaphragm. Based on this, it is necessary to provide a new method of preparing a microelectromechanical microphone to improve the degree of freedom of the diaphragm and at the same time improve the structural strength of the diaphragm.

Contents of the invention

The purpose of the present invention is to overcome the above technical problems and provide a method for preparing a microelectromechanical microphone that can improve the degree of freedom of the diaphragm while simultaneously improving the structural strength of the diaphragm.

In order to achieve the above object, an embodiment of the present invention provides a method for preparing a microelectromechanical microphone, which includes the following steps:

Select a substrate and deposit a first oxide layer on the first surface of the substrate;

Patterning a first oxide layer, the first oxide layer including a plurality of first connection vias;

Deposit a first silicon nitride layer on the surface of the first oxide layer until the first connection via hole is 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, pattern the second oxide layer, and the second oxide layer includes a second connection via hole;

Deposit a first polysilicon layer on the surface of the second oxide layer until the second connection via hole is filled, pattern the first polysilicon layer to form a diaphragm structure, and the periphery of the diaphragm structure projects orthogonally to the first baffle Fall on the first baffle;

Deposit and pattern a third oxide layer on the surface of the diaphragm structure to expose at least part of the first baffle;

A second silicon nitride layer is deposited on the surface of the third oxide layer, and the second silicon nitride layer is patterned to form a second baffle structure. The second baffle structure is connected to the first baffle structure, and the second baffle structure The orthographic projection onto the diaphragm structure falls at least partially on the periphery of the diaphragm structure;

A fourth oxide layer is deposited on the surface of the second baffle structure, a backplane material layer is deposited on the surface of the fourth oxide layer, and the patterned backplane material layer forms a backplane structure, and the backplane structure includes a plurality of acoustic through holes;

The substrate is etched on the back to form a back cavity structure corresponding to the middle main area of the back plate structure;

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.

Further, patterning the first oxide layer includes etching a ring-shaped first connection via hole along the edge of the first oxide layer at a position close to the edge of the first oxide layer.

Further, the number of the first connection via holes is multiple, and the plurality of first connection via holes are arranged at intervals in a direction from the central part to the edge part of the first oxide layer.

Further, patterning the second oxide layer includes etching a second connection via hole in a position close to an edge of the second oxide layer.

Further, the part of the first polysilicon layer that fills the second connection through hole is the extraction electrode of the diaphragm structure.

Further, 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.

Further, the ratio of the thickness of the second sub-oxide layer to the thickness of the first sub-oxide layer is 2 to 5.

Further, forming the back cavity structure includes thinning and etching the substrate from the second surface of the substrate.

Further, depositing the backplane material layer includes sequentially depositing a third silicon nitride layer and a second polysilicon layer.

Compared with related technologies, the method of manufacturing a microelectromechanical microphone provided by the present invention is to utilize the first baffle structure and the second baffle structure by respectively arranging a first baffle structure and a second baffle structure at both ends of the diaphragm structure along the vibration direction. The second baffle structure limits the displacement of the diaphragm structure in the vibration direction, thereby reducing the possibility of the diaphragm structure reaching fracture stress, thereby improving the structural strength of the diaphragm structure.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts, among which:

Figure 1 is a schematic structural diagram of a microelectromechanical microphone according to one embodiment of the present invention;

Figure 2 is a flow chart of a method for preparing a microelectromechanical microphone according to one embodiment of the present invention;

3a to 3o are schematic diagrams of a manufacturing process of a microelectromechanical microphone according to one embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Referring to FIG. 1 , a microelectromechanical microphone 100 prepared using the preparation method proposed by the present invention includes a substrate 10 and a capacitor system 20 disposed on the substrate 10 and insulatedly connected to the substrate 10 .

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 to the first surface 10A. Correspondingly, in the following description of the embodiment 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 bulk silicon process or dry etching.

The capacitive system 20 includes a diaphragm 21, a back plate 22 opposite to the diaphragm 21, and a first baffle 23 and a second baffle 24 respectively provided on the lower and upper sides of the diaphragm 21, wherein the diaphragm 21 It includes an electrode lead-out part 103 through which the diaphragm 21 is connected to the first baffle 23, and the remaining parts of the diaphragm 21 are spaced apart from the first baffle 23 in the vibration direction X. The diaphragm 21 It is spaced apart from the second baffle 24 in the vibration direction X. In this way, the diaphragm 21 is only connected to the first baffle 23 at one point through the electrode lead-out part 103, so that the remaining positions of the diaphragm 21 are not connected to other components in the vibration direction With a release degree of 21, the diaphragm 21 has a great degree of freedom in the vibration direction X, thereby improving the sensitivity of the microelectromechanical microphone 100.

In these embodiments of the present application, the electrode extraction part 103 is an extraction electrode of the diaphragm 21 .

At the same time, the projections between the peripheral portion of the diaphragm 21 and the first baffle 23 and between the peripheral portion of the diaphragm 21 and the second baffle 24 in the vibration direction The second baffle 24 plays a role in limiting the position of the diaphragm 21 when the diaphragm 21 vibrates, reducing the possibility of the diaphragm 21 being displaced to a breaking stress, thereby reducing the risk of the diaphragm 21 being damaged due to excessive displacement during vibration. The risk of breakage thus increases the structural strength of the diaphragm 21 .

When the microelectromechanical microphone 100 is powered on, the diaphragm 21 and the back plate 22 will be charged with opposite polarities, thereby forming a capacitor. When the diaphragm 21 vibrates under the action of sound waves, the space between the back plate 22 and the diaphragm 21 The distance will change, thereby causing the capacitance of the capacitor system 20 to change, thereby converting the acoustic signal into an electrical signal, thereby realizing the corresponding function of the microelectromechanical microphone 100 .

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

The first baffle 23 and the second baffle 24 may be composed of or may include a semiconductor material such as silicon. Such as 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 (for example, such as gallium arsenide or indium phosphide). Class III-V compound semiconductor, or II-VI compound semiconductor, or ternary compound semiconductor, or quaternary compound semiconductor). It may also be composed of or may include at least one of the following items: metal, dielectric material, piezoelectric material, piezoresistive material, and ferroelectric material. It can also be made of dielectric materials such as silicon nitride.

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

Please refer to Figure 3a to Figure 3o, which is a flow chart of an embodiment of a microelectromechanical microphone preparation method provided by the present invention. The preparation method is used to manufacture the microelectromechanical microphone 100 shown in Figure 1 or Figure 2. Specifically, Include the following steps.

Step S1, select the substrate 10 and prepare the first baffle 23 structure on the first surface 10A of the substrate 10, including the following sub-steps:

S11, select the substrate 10, and deposit the first oxide layer 231 on the first surface 10A of the substrate 10, as shown in FIG. 3a.

The substrate 10 is, for example, a semiconductor silicon substrate, or may be another semiconductor material substrate, such as: germanium, silicon germanium, silicon carbide, gallium nitride, indium, indium gallium nitride, indium gallium arsenide, indium gallium zinc oxide, Or other elements and/or compound semiconductors (for example, III-V compound conductors such as gallium arsenide or indium phosphide) germanium or gallium nitride and the like.

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

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

Exemplarily, 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 be 2 to 5. 3 or 4 times the thickness of a sub-oxide layer 2311.

S12, pattern the first oxide layer 231 so that the first oxide layer 231 includes a plurality of first connection vias 104, as shown in FIG. 3b.

In this step, the first connection via 104 exposes part of the first surface 10A of the substrate 10 to the first oxide layer 231 so as to contact the first silicon nitride layer 232 during the subsequent deposition process to form a connection conductive structure.

In some embodiments of the present invention, a ring-shaped first connection via 104 may be etched along the edge of the first oxide layer 231 near the edge of the first oxide layer 231 . The edge position of the first oxide layer 231 refers to the edge position on a plane parallel to the first surface 10A of the substrate 10; the annular shape of the first connection via hole 104 refers to the edge position of the first connection via hole 104 on a parallel plane. The cross-sectional shape of the first surface 10A of the substrate 10 is annular, similar to the outer contour of the first oxide layer 231 .

Preferably, in some embodiments, the number of the first connection vias 104 may be multiple, and the plurality of first connection vias 104 are spaced apart from the central part toward the edge part of the first oxide layer 231 . In order to increase the contact area between the subsequently deposited first silicon nitride layer 232 and the substrate 10, the structural consistency between the first silicon nitride layer 232 and the substrate 10 is improved.

S13, deposit the first silicon nitride layer 232 on the surface of the first oxide layer 231 until the first connection via hole 104 is filled, and pattern the first silicon nitride layer 232 to form the first baffle 23 structure, as shown in Figure 3d. Show.

The first silicon nitride layer 232 is patterned so that the first silicon nitride layer 232 is processed into a ring-shaped first baffle 23 structure.

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

S21, deposit a second oxide layer 211 on the surface of the first baffle 23 structure, and pattern the second oxide layer 211. The second oxide layer 211 includes a second connection through hole 2111, as shown in FIG. 3e.

In some embodiments, patterning the second oxide layer 211 may include etching a second connection via 2111 near an edge of the second oxide layer 211 .

S22, deposit the first polysilicon layer 212 on the surface of the second oxide layer 211 until the second connection via hole 2111 is filled, and pattern the first polysilicon layer 212 to form the diaphragm 21 structure. Wherein, the orthogonal projection of the periphery of the diaphragm 21 structure to the first baffle 23 falls on the first baffle 23, as shown in Figures 3f to 3g.

In these embodiments of the present invention, the part filled with the first polysilicon layer 212 to the second connection through hole 2111 is the connection position between the subsequent diaphragm 21 and the first baffle 23. In some embodiments, this can be set The second connection through hole 2111 is located 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, so as to release more of the diaphragm 21, so that the diaphragm 21 can vibrate in the direction of vibration. to obtain more degrees of freedom, thereby improving the sensitivity of the microelectromechanical microphone 100.

For example, in some embodiments, the structure of the diaphragm 21 can be set to correspond to the electrode extraction structure of the diaphragm 21 that is part of the second connection through hole 2111, so as to realize the connection and conduction of the diaphragm 21 at the same time.

At the same time, the orthogonal projection of the periphery of the diaphragm 21 structure to the first baffle 23 falls on the first baffle 23 , and the first baffle 23 can be used to provide the diaphragm 21 with energy on one side of the vibration direction X of the diaphragm 21 . The position limitation prevents the diaphragm 21 from 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.

Step S3, preparing a second baffle 24 structure at intervals on the side of the diaphragm 21 structure away from the first baffle 23, including the following sub-steps:

S31, deposit the third oxide layer 241 on the surface of the diaphragm 21 structure and pattern it to expose at least part of the first baffle 23, as shown in FIG. 3h.

S32, deposit the second silicon nitride layer 242 on the surface of the third oxide layer 241, and pattern the second silicon nitride layer 242 to form the second baffle 24 structure, where the second baffle 24 structure is the same as the first baffle. 23 structure is connected, and the orthographic projection of the second baffle 24 structure to the diaphragm 21 structure at least partially falls on the periphery of the diaphragm 21 structure, as shown in Figure 3i.

The structure of the second baffle 24 is connected to the structure of the first baffle 23, which means that when depositing the second silicon nitride layer 242, the second silicon nitride layer 242 can be connected with the part of the first baffle 23 exposed in step S31. contact, and when the second silicon nitride layer 242 is subsequently patterned, the portion of the second silicon nitride layer 242 that contacts the first baffle 23 is retained to allow the first baffle 23 and the second baffle 24 to travel The integrated structure improves the structural consistency of the microelectromechanical microphone 100 and provides better structural reliability.

The orthographic projection of the second baffle 24 structure to 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 the first baffle 23 and both correspond to 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 Excessive displacement occurs on one side, thereby reducing the possibility of the diaphragm 21 structure reaching fracture stress, thereby improving the structural strength of the diaphragm 21 structure.

Step S4, prepare a back plate 22 structure at intervals on the side of the second baffle 24 structure away from the diaphragm 21 structure. The back plate 22 structure includes a plurality of acoustic through holes 102, including the following sub-steps:

S41, deposit the fourth oxide layer 221 on the surface of the second baffle 24 structure, deposit the backplate material layer 222 on the surface of the fourth oxide layer 221, and pattern the backplate material layer 222 to form the backplate 22 structure. The backplate 22 The structure includes a number of acoustic vias 102, as shown in Figures 3j to 3m.

Wherein, depositing the backplane material layer 222 includes sequentially depositing a third silicon nitride layer 2221 and a second polysilicon layer 2222.

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 .

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

S51, the substrate 10 is etched on the back side to form a back cavity 101 structure corresponding to the middle body area of the back plate 22 structure, as shown in Figure 3n.

For example, in some embodiments, a grinding process can be used to thin the second surface 10B of the substrate 10, and then the second surface 10B of the substrate 10 is patterned and etched to form the back cavity 101 area, and the etching is stopped. on the first oxide layer 231.

S52, remove the third oxide layer 241 and the fourth oxide layer 221 through the acoustic through hole 102, and remove 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. 3o.

For example, BOE solution or HF vapor etching technology can be used to remove the first oxide layer 231, the second oxide layer 211, the third oxide layer 241 and the fourth oxide layer 221.

What is described above is only the embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, improvements can be made without departing from the creative concept of the present invention, but these all belong to the present invention. scope of protection.

Claims (9)

1. A method for manufacturing a microelectromechanical microphone, comprising the steps of:

selecting a substrate, and depositing a first oxide layer on a first surface of the substrate;

patterning the first oxide layer, wherein the first oxide layer comprises a plurality of first connecting through holes;

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;

depositing a second oxide layer on the surface of the first baffle structure, and patterning the second oxide layer, wherein the second oxide layer comprises a second connecting through hole;

depositing a first polysilicon layer on the surface of the second oxide layer until the second connecting through hole is filled, and patterning the first polysilicon layer to form a vibrating diaphragm structure, wherein orthographic projection of the periphery of the vibrating diaphragm structure to the first baffle plate falls on the first baffle plate;

depositing and patterning a third oxide layer on the surface of the vibrating diaphragm structure to expose at least part of the first baffle;

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 with the first baffle structure, and the orthographic projection of the second baffle structure to the vibrating diaphragm structure at least partially falls on the periphery of the vibrating diaphragm structure;

depositing a fourth oxide layer on the surface of the second baffle structure, depositing a backboard material layer on the surface of the fourth oxide layer, and patterning the backboard material layer to form a backboard structure, wherein the backboard structure comprises a plurality of acoustic through holes;

etching the substrate on the back surface to form a back cavity structure corresponding to the middle main body area of the back plate structure;

and removing the third oxide layer and the fourth oxide layer through the acoustic through hole, and removing the first oxide layer and the second oxide layer above the back cavity structure through the back cavity structure.

2. The method of claim 1, wherein patterning the first oxide layer includes etching the first connection via in a ring shape along an edge of the first oxide layer at a position near 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 connecting holes is plural, and the plural first connecting holes are sequentially arranged at intervals along the direction from the center portion to the edge portion of the first oxide layer.

4. The method of claim 1, wherein patterning the second oxide layer includes etching the second connection via at a location of the second oxide layer near an edge.

5. The method of claim 4, wherein the portion of the first polysilicon layer that fills the second connection via is an extraction electrode of the diaphragm structure.

6. The method of claim 1, wherein depositing the first oxide layer comprises sequentially depositing a first sub-oxide layer and a second sub-oxide layer, the second sub-oxide layer having a deposition thickness greater than a deposition thickness of the first sub-oxide layer.

7. The method of claim 6, wherein a ratio of a thickness of the second sub-oxide layer to a thickness of the first sub-oxide layer is 2 to 5.

8. The method of claim 1, wherein forming the back cavity structure comprises thinning and etching the substrate from the second surface of the substrate.

9. The method of claim 1, wherein depositing the backplate material layer comprises sequentially depositing a third silicon nitride layer and a second polysilicon layer.