WO2022110420A1

WO2022110420A1 - Piezoelectric mems microphone, and array thereof and preparation method therefor

Info

Publication number: WO2022110420A1
Application number: PCT/CN2020/138813
Authority: WO
Inventors: 童贝; 沈宇; 石正雨; 段炼
Original assignee: 瑞声声学科技(深圳)有限公司
Priority date: 2020-11-30
Filing date: 2020-12-24
Publication date: 2022-06-02
Also published as: CN112584283A; CN112584283B

Abstract

Provided are a piezoelectric MEMS microphone, and an array thereof and a preparation method therefor. The piezoelectric MEMS microphone comprises a substrate having a back cavity, and a piezoelectric vibrating diaphragm fixed on the substrate, wherein the piezoelectric vibrating diaphragm comprises a vibrating diaphragm layer fixed to the substrate, and a piezoelectric layer fixed on the vibrating diaphragm layer; the piezoelectric layer is continuously bent to form a wave-shaped structure; the wave-shaped structure comprises several first grooves, which are recessed from a first surface of the piezoelectric layer that faces away from the vibrating diaphragm layer, towards the vibrating diaphragm layer, and several second grooves, which are recessed from a second surface of the piezoelectric layer that is close to the vibrating diaphragm layer, facing away from the vibrating diaphragm layer; and the first grooves and the second grooves are provided in a staggered manner. In this way, the deformation and displacement of a piezoelectric layer under external sound pressure are increased, such that a voltage output is increased, thereby effectively improving the sensitivity of a piezoelectric MEMS microphone. Moreover, the residual stress of the piezoelectric layer is reduced to a certain extent, thereby prolonging the service life of the piezoelectric MEMS microphone.

Description

Piezoelectric MEMS microphone, array and method of making the same

【Technical field】

The present application relates to the technical field of acoustics and electricity, and in particular to a piezoelectric MEMS microphone, an array thereof, and a preparation method thereof.

【Background technique】

MEMS (Micro-Electro-Mechanical System, Micro-Electro-Mechanical System) microphone is a kind of electrical energy 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).

Please refer to FIG. 1, which is a MEMS microphone in the prior art. In FIG. 1, the substrate is C, the piezoelectric unit A and the diaphragm B are stacked on the substrate C in turn, and the piezoelectric unit A is flatly distributed above the diaphragm B. . In the existing structure, under the action of external sound pressure, the diaphragm is deformed first, and then the piezoelectric unit above it is also deformed. Since the piezoelectric unit A is distributed flatly, the deformation amount generated in the middle part is not very large. , resulting in a smaller output voltage and therefore lower sensitivity.

Therefore, it is necessary to provide a new piezoelectric MEMS microphone and its array and fabrication method to solve the above problems.

[Content of the invention]

The purpose of the present application is to provide a piezoelectric MEMS microphone and its array and preparation method, so as to solve the problem of small deformation due to flatly distributed piezoelectric units in the prior art, resulting in a small output voltage and low sensitivity. defect.

The technical solution of the present application is as follows: a piezoelectric MEMS microphone is provided, comprising a substrate with a back cavity and a piezoelectric vibrating film fixed on the base, wherein the piezoelectric vibrating film includes a vibrating film fixed on the base layer and the piezoelectric layer fixed on the diaphragm layer, the piezoelectric layer is continuously bent to form a wavy structure,

The wave-shaped structure includes a plurality of first grooves recessed from the first surface of the piezoelectric layer away from the diaphragm layer toward the diaphragm layer, and a first groove from the piezoelectric layer close to the diaphragm layer. A plurality of second grooves with two surfaces facing away from the diaphragm layer, the first grooves and the second grooves are arranged alternately.

Preferably, the vibrating film layer includes a plurality of escape grooves corresponding to the first grooves and a plurality of spacers disposed between adjacent escape grooves, and the spacers are flush with the surface of the piezoelectric layer. .

Preferably, the first groove is accommodated in the avoidance groove, and the spacer portion is in abutment with the second groove.

Preferably, the first groove, the second groove and the escape groove are U-shaped.

Preferably, the piezoelectric layer includes a lower electrode layer, an upper electrode layer and a first piezoelectric layer sandwiched between the upper electrode layer and the lower electrode layer, which are sequentially stacked on the diaphragm layer. .

Preferably, the piezoelectric layer includes a lower electrode layer, an upper electrode layer, a middle electrode layer, and a first electrode layer sandwiched between the upper electrode layer and the middle electrode layer, which are sequentially stacked on the diaphragm layer. Two piezoelectric layers and a third piezoelectric layer sandwiched between the lower electrode layer and the middle electrode layer.

Preferably, the diaphragm layer includes an oxide isolation layer and a main diaphragm layer stacked on the substrate in sequence.

Preferably, the piezoelectric layer includes a first piezoelectric part and a second piezoelectric part arranged in an L shape, a gap is formed between the first piezoelectric part and the second piezoelectric part, and the first piezoelectric part The piezoelectric part and the second piezoelectric part are centrally symmetric;

Or, the piezoelectric layer includes four "one"-shaped piezoelectric parts enclosed in a square shape, and a gap is provided between adjacent piezoelectric parts.

The present application also provides a MEMS microphone array, including a plurality of piezoelectric MEMS microphones as described above, and the plurality of piezoelectric MEMS microphones are arranged in an array.

The application also provides a method for preparing a piezoelectric MEMS microphone, characterized in that, the preparation method includes:

providing a substrate on which an oxide isolation layer is deposited;

A main diaphragm layer is formed by depositing on the surface of the oxide isolation layer;

patterning the surface of the main diaphragm layer to form a frame portion, a main body portion and an escape groove;

A piezoelectric layer is deposited on the surface of the main vibrating film layer after the patterning treatment, and the piezoelectric layer is etched to form an electrode portion, and the electrode portion forms a wave-shaped structure corresponding to the escape groove;

Etching the other surface of the substrate away from the main diaphragm layer to form a back cavity.

The beneficial effects of the present application are as follows: a piezoelectric MEMS microphone, an array thereof, and a preparation method thereof are provided, wherein the piezoelectric MEMS microphone comprises a substrate with a back cavity and a piezoelectric vibrating membrane fixed on the substrate, the piezoelectric MEMS microphone The electric vibrating membrane includes a vibrating membrane layer fixed on the base and a piezoelectric layer fixed on the vibrating membrane layer, the piezoelectric layer is continuously bent to form a wave-shaped structure, and the wave-shaped structure includes A plurality of first grooves recessed from the first surface of the electrical layer away from the vibrating membrane layer toward the vibrating membrane layer and a plurality of first grooves recessed away from the vibrating membrane layer from the second surface of the piezoelectric layer close to the vibrating membrane layer A plurality of second grooves are arranged alternately with the first grooves and the second grooves. Through the above methods, the deformation and displacement of the piezoelectric layer under external sound pressure are improved, thereby increasing the voltage output, effectively improving the sensitivity of the piezoelectric MEMS microphone, and reducing the residual stress of the piezoelectric layer to a certain extent. , extending the service life of piezoelectric MEMS microphones.

【Description of drawings】

1 is a schematic cross-sectional view of a prior art piezoelectric MEMS microphone;

2 is a schematic cross-sectional view of a piezoelectric MEMS microphone according to an embodiment of the present application;

3 is a flowchart of a method for manufacturing a piezoelectric MEMS microphone according to an embodiment of the present application;

4-8 are schematic diagrams of a method for manufacturing the piezoelectric MEMS microphone of FIG. 3 .

Description of drawings: 100-piezoelectric MEMS microphone; 10-substrate; 11-back cavity; 20-piezoelectric diaphragm; 21-diaphragm layer; 211-oxide isolation layer; 212-main diaphragm layer; 22-piezoelectric layer; 221-upper electrode layer; 222-lower electrode layer; 223-first piezoelectric layer; 30-first groove; 40-second groove; 50-avoidance groove; a-first surface; b- The second surface; 60-frame part; 70-body part; 80-elastic element; 90-spacing part.

【Detailed ways】

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

Please refer to FIGS. 2-8 , which are schematic cross-sectional views of a piezoelectric MEMS microphone 100 provided in an embodiment of the present application. The MEMS microphone includes a substrate 10 and a piezoelectric diaphragm 20 , and the piezoelectric diaphragm 20 is fixed on the Above the substrate 10, the substrate 10 has a back cavity 11, the piezoelectric diaphragm 20 includes a diaphragm layer 21 and a piezoelectric layer 22, the diaphragm layer 21 is stacked on the substrate 10, and the pressure The electrical layer 22 is disposed on the diaphragm layer 21 , and the piezoelectric layer 22 is pressed to drive the diaphragm layer 21 to deform in the space corresponding to the back cavity 11 of the substrate 10 , thereby generating a voltage signal.

The piezoelectric layer 22 is continuously bent to form a wave-shaped structure, and the wave-shaped structure includes a plurality of first surfaces recessed from the first surface a of the piezoelectric layer 22 away from the diaphragm layer 21 toward the diaphragm layer 21 . A groove 30 and a plurality of second grooves 40 recessed from the second surface b of the piezoelectric layer 21 close to the diaphragm layer 21 and away from the diaphragm layer 21 , the first grooves 30 and the The second grooves 40 are alternately arranged to form the piezoelectric layer 22 of the wave structure on the diaphragm layer 21 . Preferably, a plurality of first grooves 30 are evenly distributed on the first surface a, and a plurality of second grooves 40 are evenly distributed on the second surface b.

In an optional embodiment, the diaphragm layer 21 includes a plurality of avoidance grooves 50 corresponding to the first grooves 30 , and the avoidance grooves 50 are close to the pressure from the diaphragm layer 21 . A surface of one side of the electrical layer 22 is recessed toward the back cavity 11 , and spacers 90 are provided between adjacent escape grooves 50 .

In an optional embodiment, the second groove 40 corresponds to the spacer portion 90 , and the second surface b corresponding to the second groove 40 abuts against the surface of the spacer portion 90 on the side away from the back cavity 11 , The first groove 30 is accommodated in the escape groove 50 , and the second surface b corresponding to the first groove 30 is in contact with the bottom of the escape groove 50 , so that the piezoelectric layer The second surface b of 22 is in contact with the surface of the side of the diaphragm layer 21 away from the back cavity 11 .

In an optional embodiment, in order to facilitate processing, the first groove 30 , the second groove 40 and the escape groove 50 are all U-shaped, of course, the specific shape is not limited by the shape shown in the figure .

In an optional embodiment, the piezoelectric layer 22 includes a lower electrode layer 222, an upper electrode layer 221 stacked on the diaphragm layer 21 in sequence, and a lower electrode layer 221 and an upper electrode layer 221 sandwiched between the upper electrode layer 221 and the The first piezoelectric layer 223 between the lower electrode layers 222 . Optionally, the piezoelectric layer 223 may further include a lower electrode layer 222 , an upper electrode layer 221 , a middle electrode layer (not shown in the figure), which are sequentially stacked on the diaphragm layer 21 , and sandwiched on the upper electrode layer 221 . A second piezoelectric layer (not shown in the figure) between the electrode layer 221 and the middle electrode layer and a third piezoelectric layer (not shown in the figure) sandwiched between the lower electrode layer 222 and the middle electrode layer ). The upper electrode layer 221 is a combination of one or more materials selected from molybdenum, titanium-molybdenum alloy, platinum, aluminum or tungsten; the lower electrode layer 222 and the middle electrode layer are one or more of aluminum, molybdenum, gold, and titanium nitride. A combination of various materials. The first piezoelectric layer 223, the second piezoelectric layer and the third piezoelectric layer are one or a combination of materials selected from aluminum nitride, zinc oxide, lead zirconate titanate, and aluminum scandium nitride; in this embodiment Among them, the number of film layers of the piezoelectric layer 22 may be three or five layers as exemplified above, but in other embodiments, the number of film layers of the piezoelectric layer 22 may also be three or more layers; and the pressure The edges of each film layer of the electrical layer 22 are flush with each other. The piezoelectric layer 22 is arranged in a multi-layer film structure, so that the bending radius of the piezoelectric layer 22 is larger, and a larger strain will be generated when the same bending angle is generated, thereby generating a larger output signal.

In an optional implementation manner, the diaphragm layer 21 includes an oxide isolation layer 211 and a main diaphragm layer 212 stacked on the substrate 10 in sequence, and the oxide isolation layer 211 includes but is not limited to silicon dioxide , the main diaphragm layer 212 is one or more of polyethylene, polysilicon, silicon nitride or silicon carbide. Edges of the oxide isolation layer 211 and the main diaphragm layer 212 are flush. Optionally, the diaphragm layer 21 in the embodiment of the present application includes a frame portion 60 , a main body portion 70 and an elastic element 80 , the frame portion 60 is fixedly connected to the base 10 , and the main body portion 70 is arranged at intervals inside the frame portion 60 and is connected to the frame portion 60 . The back cavity 11 of the substrate 10 corresponds to the back cavity 11 , that is, the main body portion 70 is suspended above the back cavity 11 , and the piezoelectric layer 22 is stacked on the side of the main body portion 70 away from the back cavity 11 . The outer edge of the main body portion 70 is flush; the elastic unit 33 is generally arranged in a comb-tooth shape, and the elastic unit 33 connects the frame portion 60 and the main body portion 70 .

In an optional embodiment, the piezoelectric layer 22 is a rectangular structure whose planar geometric center overlaps with the planar geometric center of the main body portion 70 . When the piezoelectric layer 22 has a rectangular structure, since the entire microphone can be regarded as a balanced and symmetrical structure, the geometric center of the main body portion 70 can also be regarded as the geometric center of the piezoelectric layer 22 . In the MEMS processing process, only a small amount of material base can be etched away to achieve the structural features under the condition of ensuring the above-mentioned structural features. In this embodiment, the piezoelectric layer 22 includes two piezoelectric parts arranged in an L shape, a gap is formed between the two piezoelectric parts, and the two piezoelectric parts are centrally symmetrical. It can be understood that the two piezoelectric parts and the gap enclose a square piezoelectric layer 22 . Optionally, the piezoelectric layer 22 includes four in-line voltage parts and a gap between adjacent piezoelectric parts, and the four in-line voltage parts and the gap surround the piezoelectric layer 22 forming a square structure. . Of course, in other embodiments, the piezoelectric layer 22 can also be set in other shapes, and also include other shapes and numbers of piezoelectric parts.

The embodiment of the present application also provides a MEMS microphone array, the MEMS microphone array includes a plurality of piezoelectric MEMS microphones 100 described above, and the plurality of piezoelectric MEMS microphones 100 are arranged in an array and combined by the connection of adjacent frame parts 60 into a single structure. The piezoelectric MEMS microphone 100 can be extended through a combination of multiple structural forms, such as repetition, symmetry, or mirror image, to form a MEMS microphone array structure with function amplification or expansion. In this application, the array structure specifically refers to the MEMS microphone 100 described above as a template extending along any or more directions, and connected to each other in the form of a repeating unit structure, forming a rectangle in the form of 2ⅹ2, 3ⅹ3, or 4ⅹ4. The array structure, of course, can also be in the form of 3ⅹ4 or 4ⅹ5.

In the piezoelectric MEMS microphone 100 of the embodiment of the present application, by modifying the flat piezoelectric unit in the prior art in FIG. 1 into the piezoelectric layer 22 of the wave-shaped structure of the present application in FIG. The deformation and displacement under the sound pressure, thereby increasing the voltage output, effectively improving the sensitivity of the piezoelectric MEMS microphone 100; on the other hand, the groove structure (the first groove 30 and the second groove) The introduction of 40) can also reduce the residual stress of the piezoelectric layer structure to a certain extent, and prolong the service life of the piezoelectric MEMS microphone 100 .

Referring to FIGS. 3 to 8 , an embodiment of the present application further provides a method for manufacturing a piezoelectric MEMS microphone 100 , which specifically includes the following steps:

S1, a substrate is provided, and an oxide isolation layer is deposited on the surface of the substrate;

Specifically, the substrate 10 is a micro-silicon substrate. Before depositing the oxide isolation layer 211, the substrate 10 can be cleaned. The cleaned silicon micro-substrate is used as the substrate 10 for MEMS etching and molding. The substrate 10 It can be the substrate of a single piezoelectric MEMS microphone 100, or it can be the substrate of the MEMS microphone array that is integrally formed with the microphone structure. The oxide isolation layer 211 can be silicon dioxide, and is formed by a low pressure chemical vapor deposition method or a plasma enhanced chemical vapor deposition method.

S2, depositing and forming a main diaphragm layer on the surface of the oxide isolation layer;

Specifically, the main diaphragm layer 212 can be deposited on the surface of the oxide isolation layer 211 by chemical vapor deposition, which is one of plasma-enhanced chemical vapor deposition or low-pressure chemical vapor deposition; The diaphragm layer 212 is one or more of polyethylene, polysilicon, silicon nitride or silicon carbide.

S3, patterning the surface of the main diaphragm layer to form a frame portion, a main body portion, and an escape groove;

Specifically, the main diaphragm layer 212 is etched to form a space-saving part, and the space-avoiding part separates the main diaphragm layer 212 to form the frame part 60 and the main body part 70 , and the space-avoiding part can be used to set the connection between the main body part 70 and the frame part 60 of the elastic element 80. Then, a plurality of spaced-apart grooves 50 are formed by etching on the main body portion 70 . The spaced-apart grooves 50 separate the main diaphragm layer 212 into a plurality of spacers 90 . Since the deposited surface of the main diaphragm layer 212 is flush, the surfaces of the formed plurality of spacers 90 on the side away from the substrate are also flush.

S4, depositing a piezoelectric layer on the surface of the patterned main diaphragm layer, etching the piezoelectric layer to form an electrode portion, and forming a wavy structure at the electrode portion corresponding to the escape groove;

Specifically, the piezoelectric layer 22 is deposited on the main body part 70 , and the edge of the piezoelectric layer 22 is flush with the edge of the main body part 70 . Since the avoidance groove 50 is formed in step S3, the first groove 30 is formed at the position corresponding to the avoidance groove 50 after the piezoelectric layer 22 is deposited. For the piezoelectric layer 22, the adjacent first groove 30 The second groove 40 is formed therebetween, and the second groove 40 and the first groove 30 are alternately arranged on two opposite surfaces of the piezoelectric layer 22 to form a wave-shaped structure. In addition, the second groove 40 is in correspondence with the unetched spacer 90 on the main diaphragm, and preferably, the first groove 30 , the second groove 40 and the escape groove 50 are U-shaped.

Specifically, the piezoelectric layer 22 can be deposited three times after deposition of the lower electrode layer 222, the first piezoelectric layer 223, and the upper electrode layer 221 in sequence, or after five times of silence, the lower electrode layer 222, the third piezoelectric layer, Of course, the number of depositions of the middle electrode layer, the second piezoelectric layer and the upper electrode layer 221, and of course the piezoelectric layer 22, may not be limited to the above three and five depositions. Optionally, the upper electrode layer 221 is a combination of one or more materials selected from molybdenum, titanium-molybdenum alloy, platinum, aluminum or tungsten; the lower electrode layer 222 and the middle electrode layer are made of aluminum, molybdenum, gold, and titanium nitride. a combination of one or more materials. The first piezoelectric layer 223 , the second piezoelectric layer and the third piezoelectric layer are one or a combination of materials selected from aluminum nitride, zinc oxide, lead zirconate titanate, and aluminum scandium nitride.

Specifically, dry etching is used to form a gap and a plurality of electrode parts, such as two centrally symmetric L-shaped electrode parts, or four in-line electrode parts surrounded by a square, with an interval between two adjacent electrode parts. set up.

S5, etching the other surface of the substrate away from the main diaphragm layer to form a back cavity.

Specifically, inductively coupled plasma (ICP) deep etching is performed on the other surface of the substrate 10 away from the main diaphragm layer 212 first, and the etching stops at the oxide isolation layer 211 to form the back cavity 11 region, and then the buffer oxide is used for etching The oxide isolation layer 211 is released by liquid (BOE solution) or hydrofluoric acid (HF) vapor phase etching technology, and finally the piezoelectric MEMS microphone 100 of the embodiment of the present application is formed.

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

Claims

A piezoelectric MEMS microphone, comprising a base having a back cavity and a piezoelectric vibrating film fixed on the base, the piezoelectric vibrating film comprising a vibrating film layer fixed on the base and a vibrating film layer fixed on the base The piezoelectric layer above is characterized in that the piezoelectric layer is continuously bent to form a wave-shaped structure,

The wave-shaped structure includes a plurality of first grooves recessed from the first surface of the piezoelectric layer away from the diaphragm layer toward the diaphragm layer, and a first groove from the piezoelectric layer close to the diaphragm layer. A plurality of second grooves with two surfaces facing away from the diaphragm layer, the first grooves and the second grooves are arranged alternately.
The piezoelectric MEMS microphone according to claim 1, wherein the diaphragm layer comprises a plurality of avoidance grooves corresponding to the first grooves and a plurality of spacers disposed between adjacent avoidance grooves, Several spacers are flush with the surface of the piezoelectric layer.
The piezoelectric MEMS microphone according to claim 2, wherein the first groove is accommodated in the escape groove, and the spacer portion is in contact with the second groove.
The piezoelectric MEMS microphone according to claim 2, wherein the first groove, the second groove and the escape groove are U-shaped.
The piezoelectric MEMS microphone according to claim 1, wherein the piezoelectric layer comprises a lower electrode layer, an upper electrode layer, and an upper electrode layer sandwiched between the upper electrode layer and the diaphragm layer. the first piezoelectric layer between the lower electrode layers.
The piezoelectric MEMS microphone according to claim 1, wherein the piezoelectric layer comprises a lower electrode layer, an upper electrode layer, a middle electrode layer, and a layer sandwiched between the A second piezoelectric layer between the upper electrode layer and the middle electrode layer and a third piezoelectric layer sandwiched between the lower electrode layer and the middle electrode layer.
The piezoelectric MEMS microphone according to claim 1, wherein the diaphragm layer comprises an oxide isolation layer and a main diaphragm layer sequentially stacked on the substrate.
The piezoelectric MEMS microphone according to any one of claims 1-7, wherein the piezoelectric layer comprises a first piezoelectric part and a second piezoelectric part arranged in an L shape, the first piezoelectric part and There is a gap between the second piezoelectric parts, and the first piezoelectric part and the second piezoelectric part are centrally symmetric;

Or, the piezoelectric layer includes four "one"-shaped piezoelectric parts enclosed in a square shape, and a gap is provided between adjacent piezoelectric parts.
A MEMS microphone array, characterized in that it includes a plurality of piezoelectric MEMS microphones according to any one of claims 1-8, and the plurality of piezoelectric MEMS microphones are arranged in an array.
A preparation method of a piezoelectric MEMS microphone, characterized in that the preparation method comprises:

providing a substrate on which an oxide isolation layer is deposited;

A main diaphragm layer is formed by depositing on the surface of the oxide isolation layer;

patterning the surface of the main diaphragm layer to form a frame portion, a main body portion and an escape groove;

A piezoelectric layer is deposited on the surface of the main vibrating film layer after the patterning treatment, and the piezoelectric layer is etched to form an electrode portion, and the electrode portion forms a wave-shaped structure corresponding to the escape groove;

Etching the other surface of the substrate away from the main diaphragm layer to form a back cavity.