WO2022007016A1

WO2022007016A1 - Piezoelectric microphone and preparation process therefor

Info

Publication number: WO2022007016A1
Application number: PCT/CN2020/104047
Authority: WO
Inventors: 童贝; 石正雨; 沈宇; 李杨
Original assignee: 瑞声声学科技(深圳)有限公司; 瑞声科技（南京）有限公司
Priority date: 2020-07-10
Filing date: 2020-07-24
Publication date: 2022-01-13
Also published as: CN111669690A

Abstract

The present invention provides a piezoelectric microphone and a preparation process therefor. The piezoelectric microphone comprises a substrate with a back cavity and a piezoelectric vibration diaphragm arranged on the substrate, wherein the piezoelectric vibration diaphragm comprises a vibration diaphragm layer fixed on the substrate and a piezoelectric unit fixed on the vibration diaphragm layer; and the piezoelectric microphone further comprises a housing covering the vibration diaphragm layer from above, wherein the housing and the vibration diaphragm layer define an accommodating cavity for accommodating the piezoelectric unit, with the accommodating cavity being a vacuum. The present invention can increase the output voltage of the piezoelectric unit, so as to improve the sensitivity of the piezoelectric microphone.

Description

Piezoelectric microphone and preparation process thereof

technical field

The invention belongs to the technical field of microphones, and in particular relates to a piezoelectric microphone and a preparation process thereof.

Background technique

MEMS (Micro-Electro-Mechanical Micro-electromechanical system) microphone is a kind of electric power sound transducer produced by micro-machining technology, which has the characteristics of small size, good frequency response characteristics and low noise. With the development of miniaturization and thinning of electronic devices, MEMS microphones are more and more widely used in these devices. Piezoelectric MEMS microphones have many advantages over traditional condenser MEMS microphones, including dust and water resistance and higher maximum sound pressure output (AOP).

In the related art, the diaphragm of a piezoelectric MEMS microphone is composed of a plurality of diaphragms, and the plurality of diaphragms are fixed on a substrate with a back cavity through elastic connection, and the upper and lower parts of the diaphragm are air. After the piezoelectric MEMS microphone is packaged, the airtight environment hinders the movement of the vibrating membrane, thereby reducing the output voltage of the piezoelectric unit and greatly reducing the sensitivity of the MEMS microphone.

technical problem

The purpose of the present invention is to provide a piezoelectric microphone and a manufacturing process thereof, aiming at increasing the output voltage of the piezoelectric unit and improving the sensitivity of the piezoelectric microphone.

technical solutions

The technical solution of the present invention is as follows: a piezoelectric microphone, comprising a base having a back cavity and a piezoelectric vibrating film arranged on the base, the piezoelectric vibrating film comprising a vibrating film layer fixed on the base and a piezoelectric unit fixed on the diaphragm layer, characterized in that: the piezoelectric microphone further includes a casing covering the diaphragm layer, the casing and the diaphragm layer are enclosed An accommodating cavity for accommodating the piezoelectric unit is formed, and the accommodating cavity is a vacuum environment.

Further, the casing is made of silicon, silicon nitride, polyethylene or glass.

Further, the base includes a side wall enclosing the back cavity, the orthographic projection of the piezoelectric unit along the vibration direction of the diaphragm layer and the positive projection of the side wall along the vibration direction of the diaphragm layer. The projections partially overlap.

Further, the diaphragm layer is an integral continuous structure.

Further, the piezoelectric unit includes a plurality of piezoelectric sheets, the plurality of piezoelectric sheets are arranged symmetrically in the center, and two adjacent piezoelectric sheets are arranged at intervals.

Further, the piezoelectric unit includes a first electrode layer, a piezoelectric layer and a second electrode layer stacked on the vibrating film layer in sequence, and the first electrode layer and the second electrode layer are made of aluminum, Molybdenum or titanium material, the piezoelectric layer is made of aluminum nitride, zinc oxide, scandium-doped aluminum nitride or lead zirconate titanate piezoelectric ceramic material.

Further, the diaphragm layer is made of aluminum nitride, polysilicon, silicon dioxide or silicon nitride.

The invention also provides a preparation process of the piezoelectric microphone, comprising the following steps:

Step S1: providing a substrate, and depositing a first oxide layer on the surface of the substrate;

Step S2: depositing a diaphragm layer on the surface of the first oxide layer;

Step S3: depositing a piezoelectric unit on the surface of the diaphragm layer;

Step S4: etching the piezoelectric unit;

Step S5: depositing on the surface of the piezoelectric unit a casing covering the vibrating membrane layer, the casing and the vibrating membrane are laminated to form an accommodation cavity for accommodating the piezoelectric unit;

Step S6: etching the other surface of the substrate away from the diaphragm layer to form a back cavity.

Further, step S5 specifically includes:

Step S51: Cover the surface of the piezoelectric unit with a second oxide layer, and perform polishing and patterning treatment;

Step S52: depositing a first sealing layer on the surface of the second oxide layer;

Step S53: etching the first sealing layer to form a release hole, and releasing the second oxide layer to form the receiving cavity;

Step S54: sealing the release hole.

Further, the step S5 specifically includes:

Step S501: depositing a peripheral wall layer on the edge of the diaphragm layer, the peripheral wall layer surrounding the piezoelectric unit;

Step S502: providing a second sealing layer;

Step S503 : bonding the peripheral wall layer and the second sealing layer to form the casing.

beneficial effect

The beneficial effect of the present invention is that: by arranging a casing above the diaphragm layer, the casing and the diaphragm are laminated to form an accommodation cavity for accommodating the piezoelectric unit, and the accommodation cavity is a vacuum environment, so the diaphragm layer is subjected to vibration during vibration. The air damping is greatly reduced, and the output voltage of the piezoelectric unit will increase under the same sound pressure, which effectively improves the sensitivity of the microphone.

Description of drawings

1 is a schematic diagram of the overall structure of a piezoelectric microphone provided by a first embodiment of the present invention;

2 is a schematic diagram of an exploded structure of the piezoelectric microphone provided by the first embodiment of the present invention;

Fig. 3 is the A-A direction sectional schematic diagram of Fig. 1;

Fig. 4 is the preparation flow chart of the piezoelectric microphone provided by the second embodiment of the present invention;

5 to 13 are schematic diagrams of the manufacturing process of the piezoelectric microphone provided by the second embodiment of the present invention;

14 is a schematic diagram of a preparation process for depositing a peripheral wall layer on the edge of the diaphragm layer according to the third embodiment of the present invention;

15 is a schematic diagram of a preparation process for providing a second sealing layer on the peripheral wall layer according to the third embodiment of the present invention.

Embodiments of the present invention

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Example:

Please refer to FIG. 1 to FIG. 2 , which is a piezoelectric microphone provided by the first embodiment of the present invention, including a substrate 1 having a back cavity 4 and a piezoelectric vibrating membrane 2 disposed on the substrate 1 . The piezoelectric vibrating membrane 2 It includes a diaphragm layer 21 fixed on the base 1 and a piezoelectric unit 22 fixed on the diaphragm layer 21 . The piezoelectric unit 22 is pressed to drive the diaphragm layer 21 to deform in the space above the back cavity 4, thereby generating a voltage signal.

In this embodiment, as shown in FIG. 2 , the piezoelectric microphone further includes a casing 3 covering the diaphragm layer 21 . The casing 3 and the diaphragm layer 21 enclose a receiving cavity 5 for accommodating the piezoelectric unit 22 . , the containment cavity 5 is a vacuum environment. By arranging the casing 3 covering the diaphragm layer 21, the casing 3 and the diaphragm layer 21 enclose the accommodation cavity 5 for accommodating the piezoelectric unit 22, and the accommodation cavity 5 is a vacuum environment, so the diaphragm layer 21 is in the The air damping received during vibration is greatly reduced. Compared with the related art, the output voltage of the piezoelectric unit 22 will increase under the same sound pressure, which effectively improves the sensitivity of the microphone.

Specifically, the housing 3 includes a peripheral wall 31 disposed along the periphery of the diaphragm layer 21 and a top wall 32 covering the side of the peripheral wall 31 away from the diaphragm layer 21 . The peripheral wall 31 and the diaphragm layer 21 are fixed and the peripheral wall 31 is connected to The edges of the diaphragm layer 21 are flush. The peripheral wall 31 is flush with the edge of the diaphragm layer 21 , so that the piezoelectric microphone is balanced and stable as a whole and is more beautiful. The diaphragm layer 21 in this embodiment has an overall continuous structure, and there is no fault or gap in the diaphragm layer 21 , so it can ensure that a completely vacuum vacuum chamber 5 is formed above the diaphragm layer 21 .

Preferably, the casing 3 is made of silicon, silicon nitride, polyethylene or glass. Of course, the casing 3 can also be a combination of silicon nitride, polyethylene or glass.

Further, the substrate 1 includes a side wall 11 enclosing the back cavity 4 , and the orthographic projection of the piezoelectric unit 22 along the vibration direction of the diaphragm layer 21 partially overlaps with the orthographic projection of the side wall 11 along the vibration direction of the diaphragm layer 21 . That is to say, the edge of the piezoelectric unit 22 is at least partially laterally beyond the edge of the back cavity 4, so that when the diaphragm layer 21 vibrates, the part of the piezoelectric unit 22 corresponding to the edge of the back cavity 4 will be subjected to greater stress , thereby further increasing the output voltage of the piezoelectric unit 22 .

The piezoelectric unit 22 of this embodiment includes a first electrode layer 222 , a piezoelectric layer 223 and a second electrode layer 224 sequentially stacked on the diaphragm layer 21 , the first electrode layer 222 , the piezoelectric layer 223 and the second electrode The edges of layers 224 are flush with each other. The substrate 1 is a micro-silicon substrate, the diaphragm layer 21 is disposed on the substrate 1, the first electrode layer 222 is disposed on the diaphragm layer 21, the piezoelectric layer 223 is disposed on the first electrode layer 222, and the second electrode layer 224 is disposed on the piezoelectric layer 223 . The first electrode layer 222 and the second electrode layer 224 are made of aluminum, molybdenum or titanium, or a combination of the above materials, and the piezoelectric layer 223 is made of aluminum nitride, scandium-doped aluminum nitride, zinc oxide, or zirconium titanate Lead piezoelectric ceramic material, or a combination of the above materials, the diaphragm layer 21 is made of aluminum nitride, polysilicon, silicon dioxide or silicon nitride, or a combination of the above materials. In this embodiment, the number of layers of the piezoelectric unit 22 is three. In other embodiments, the number of layers of the piezoelectric unit 22 may be four, five, six or more, which is not done in this embodiment. limit.

The piezoelectric unit 22 includes a plurality of piezoelectric sheets 221 , the plurality of piezoelectric sheets 221 are arranged symmetrically in the center, and two adjacent piezoelectric sheets 221 are arranged at intervals. Preferably, the piezoelectric unit 22 includes four piezoelectric sheets 221, and the four piezoelectric sheets 221 are all triangular in structure, and the sizes of the four piezoelectric sheets 221 are equal, and the four piezoelectric sheets 221 are enclosed to form a square structure. The piezoelectric unit 22 is composed of a plurality of piezoelectric sheets 221 spaced apart from each other, and each piezoelectric sheet 221 extends from above the central position of the diaphragm layer 21 to above the edge of the diaphragm layer 21, so that the center of the piezoelectric region can be The area has a larger deformation amount, thereby improving the sensitivity of the piezoelectric microphone and improving the uniformity of product performance, and the piezoelectric sheets 221 can be set to have equal intervals to improve the consistency and uniformity of the product structure. In other possible implementations, the piezoelectric sheet 221 may also be a fan-shaped structure, and a plurality of fan-shaped piezoelectric sheets 221 are enclosed to form a circular structure.

Referring to FIG. 4 , the second embodiment of the present invention also provides a manufacturing process for a piezoelectric microphone, including the following steps:

Step S1: providing a substrate 1, and depositing a first oxide layer 6 on the surface of the substrate 1, as shown in FIG. 5;

Specifically, the substrate 1 is a micro-silicon substrate, and before depositing the first oxide layer 6, the substrate 1 can be cleaned first. The first oxide layer 6 can be silicon dioxide and is formed by a low pressure chemical vapor deposition method or a plasma enhanced chemical vapor deposition method.

Step S2: depositing a diaphragm layer 21 on the surface of the first oxide layer 6, as shown in FIG. 6;

Specifically, the diaphragm layer 21 is made of aluminum nitride, polysilicon, silicon dioxide, polymer or silicon nitride material, or a combination of the above materials.

Step S3: depositing a piezoelectric unit 22 on the surface of the diaphragm layer 21, as shown in FIG. 7;

Specifically, it includes the following sub-steps:

Step S31 : depositing a first electrode layer 222 on the surface of the diaphragm layer 21 . The first electrode layer 222 is made of aluminum, molybdenum, or titanium, or a combination of the above materials.

Step S32: depositing a piezoelectric layer 223 on the surface of the first electrode layer 222, the piezoelectric layer 223 is made of aluminum nitride, scandium-doped aluminum nitride, zinc oxide or lead zirconate titanate piezoelectric ceramic material, or a variety of the above materials. combination.

Step S33 : depositing a second electrode layer 224 on the surface of the piezoelectric layer 223 . The second electrode layer 224 is made of aluminum, molybdenum or titanium, or a combination of the above materials.

Step S4: etching the piezoelectric unit 22, as shown in FIG. 8;

Specifically, dry etching is used to form a plurality of piezoelectric sheets 221 , the plurality of piezoelectric sheets 221 are arranged symmetrically in the center, and two adjacent piezoelectric sheets 221 are arranged at intervals.

Step S5 : depositing a casing 3 covering the diaphragm layer 21 on the surface of the piezoelectric unit 22 , the casing 3 and the diaphragm layer 21 are enclosed to form an accommodation cavity 5 for accommodating the piezoelectric unit 22 ;

It should be noted that step S5 is prepared in a vacuum environment, so as to ensure that the finally formed containing cavity 5 is in a vacuum environment. Specifically, step S5 includes the following sub-steps:

Step S51 : Cover the surface of the piezoelectric unit 22 with the second oxide layer 7 , and perform polishing and patterning treatment, as shown in FIG. 9 . Specifically, the second oxide layer 7 is silicon dioxide.

Step S52 : depositing a first sealing layer 8 on the surface of the second oxide layer 7 , as shown in FIG. 10 ; the first sealing layer 8 is made of silicon nitride or polymer material.

Step S53 : etching the first sealing layer 8 to form release holes 81 , releasing the second oxide layer 7 to form the receiving cavity 5 , as shown in FIG. 11 ;

The release hole 81 is used to remove the second oxide layer 7 located in the central main body region between the first sealing layer 8 and the diaphragm layer 21 until the diaphragm layer 21 is exposed, forming a receiving cavity 5 for accommodating the piezoelectric unit 22 .

Step S54 : sealing the release hole 81 , as shown in FIG. 12 . The same material as the first sealing layer 8 may be deposited in the area of the release hole 81 to seal the release hole 81 .

Step S6 : etching the other surface of the substrate 1 away from the diaphragm layer 21 to form a back cavity 4 , as shown in FIG. 13 . Specifically, ICP deep etching is first performed on the other surface of the substrate 1 away from the diaphragm layer 21, and the etching stops at the first oxide layer 6 to form the back cavity 4 region, and then BOE solution or HF vapor phase etching technology is used to etch the first surface of the first oxide layer 6. The oxide layer 6 is released, and finally the piezoelectric microphone of the embodiment of the present invention is formed.

The third embodiment of the present invention provides a manufacturing process of a piezoelectric microphone. The only difference between the third embodiment and the second embodiment is that the method for depositing the casing 3 on the surface of the piezoelectric unit 22 is different. Specifically, it includes the following steps:

Step S11: providing a substrate 1, and depositing a first oxide layer 6 on the surface of the substrate 1;

Step S21: depositing a diaphragm layer 21 on the surface of the first oxide layer 6;

Step S31: depositing the piezoelectric unit 22 on the surface of the diaphragm layer 21;

Step S41: etching the piezoelectric unit 22;

Step S51 : forming a casing 3 covering the diaphragm layer 21 on the surface of the piezoelectric unit 22 , and the casing 3 and the diaphragm layer 21 enclose a receiving cavity 5 for accommodating the piezoelectric unit 22 ;

Step S51 includes the following sub-steps:

Step S501 : depositing a peripheral wall layer 70 on the edge of the diaphragm layer 21 , and the peripheral wall layer 70 surrounds the piezoelectric unit 22 , as shown in FIG. 14 .

Step S502 : providing the second sealing layer 80 , as shown in FIG. 15 .

Step S503 : bonding the peripheral wall layer 70 and the second sealing layer 80 to seal the top of the peripheral wall layer 70 and the second sealing layer 80 to form the accommodation cavity 5 for accommodating the piezoelectric unit 22 . Specifically, the peripheral wall layer 70 and the second sealing layer 80 may be bonded by eutectic bonding, anodic bonding or low temperature soldering.

Step S61 : etching the other surface of the substrate 1 away from the diaphragm layer 21 to form the back cavity 4 .

To sum up, in the piezoelectric microphone provided by the embodiment of the present invention, the casing 3 is arranged above the diaphragm layer 21 , and the casing 3 and the diaphragm layer 21 enclose a vacuum cavity 5 for accommodating the piezoelectric unit 22 . Therefore, the air damping received by the diaphragm layer 21 during vibration is greatly reduced, and the output voltage of the piezoelectric unit 22 will increase under the same sound pressure, which effectively improves the sensitivity of the microphone.

The above are only the embodiments 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 inventive concept of the present invention, but these belong to the present invention. scope of protection.

Claims

A piezoelectric microphone, comprising a base with a back cavity and a piezoelectric vibrating film arranged on the base, the piezoelectric vibrating film comprising a vibrating film layer fixed on the base and a vibrating film fixed on the vibrating film The piezoelectric unit on the layer is characterized in that: the piezoelectric microphone further comprises a casing covering the diaphragm layer, and the casing and the diaphragm are laminated to form an enclosure for accommodating the piezoelectric The accommodating cavity of the unit, the accommodating cavity is a vacuum environment.
The piezoelectric microphone of claim 1, wherein the housing is made of silicon, silicon nitride, polyethylene or glass.
The piezoelectric microphone according to claim 1, wherein the base comprises a side wall enclosing the back cavity, and the orthographic projection of the piezoelectric unit along the vibration direction of the diaphragm layer is the same as the side wall of the back cavity. The orthographic projections of the side walls along the vibration direction of the diaphragm layer overlap.
The piezoelectric microphone according to claim 1, wherein the diaphragm layer is an integral continuous structure.
The piezoelectric microphone according to claim 1, wherein the piezoelectric unit comprises a plurality of piezoelectric sheets, and the plurality of the piezoelectric sheets are arranged symmetrically in the center, and between two adjacent piezoelectric sheets interval setting.
The piezoelectric microphone according to claim 1, wherein the piezoelectric unit comprises a first electrode layer, a piezoelectric layer and a second electrode layer sequentially stacked on the diaphragm layer, the first electrode layer An electrode layer and the second electrode layer are made of aluminum, molybdenum or titanium, and the piezoelectric layer is made of aluminum nitride, zinc oxide, scandium-doped aluminum nitride or lead zirconate titanate piezoelectric ceramic material.
The piezoelectric microphone of claim 1, wherein the diaphragm layer is made of aluminum nitride, polysilicon, silicon dioxide or silicon nitride.
A preparation process for a piezoelectric microphone, comprising the following steps:

Step S1: providing a substrate, and depositing a first oxide layer on the surface of the substrate;

Step S2: depositing a diaphragm layer on the surface of the first oxide layer;

Step S3: depositing a piezoelectric unit on the surface of the diaphragm layer;

Step S4: etching the piezoelectric unit;

Step S5: depositing on the surface of the piezoelectric unit a casing covering the vibrating membrane layer, the casing and the vibrating membrane are laminated to form an accommodation cavity for accommodating the piezoelectric unit;

Step S6: etching the other surface of the substrate away from the diaphragm layer to form a back cavity.
The preparation process according to claim 8, wherein the step S5 specifically comprises:

Step S51: Cover the surface of the piezoelectric unit with a second oxide layer, and perform polishing and patterning treatment;

Step S52: depositing a first sealing layer on the surface of the second oxide layer;

Step S53: etching the first sealing layer to form a release hole, and releasing the second oxide layer to form the receiving cavity;

Step S54: sealing the release hole.
The preparation process according to claim 8, wherein the step S5 specifically comprises:

Step S501: depositing a peripheral wall layer on the edge of the diaphragm layer, the peripheral wall layer surrounding the piezoelectric unit;

Step S502: providing a second sealing layer;

Step S503 : bonding the peripheral wall layer and the second sealing layer to form the casing.