CN118450310A - Audio chip assembly based on composite piezoelectric film and preparation method - Google Patents

Abstract

The application provides an audio chip assembly based on a composite piezoelectric film and a preparation method thereof, wherein the audio chip assembly comprises a substrate, and a lower electrode, a first piezoelectric layer, a middle electrode, a second piezoelectric layer and an upper electrode which are sequentially deposited on the substrate, wherein the first piezoelectric layer has a low dielectric constant and a low piezoelectric coefficient, and the second piezoelectric layer has a high dielectric constant and a high piezoelectric coefficient. The audio chip assembly based on the composite piezoelectric film, provided by the application, combines the piezoelectric layer with low dielectric loss and poor piezoelectric performance and the piezoelectric layer with high dielectric loss and high piezoelectric performance into a bimorph or multichip structure, and the advantages of the piezoelectric layers are complementary, so that the whole piezoelectric film has good piezoelectric performance and dielectric performance.

Description

Audio chip assembly based on composite piezoelectric film and preparation method

Technical Field

The present application relates to the field of semiconductor manufacturing technology, and in particular to an audio chip assembly based on a composite piezoelectric film and a preparation method thereof.

Background technique

An acoustic transducer is an energy conversion device that can convert sound signals into electrical signals in different ways. A piezoelectric acoustic transducer is an energy conversion device that uses the piezoelectric effect to convert sound signals into electrical signals. For example, piezoelectric MEMS microphones and speakers are typical piezoelectric acoustic transducers. In recent years, piezoelectric MEMS audio chips have been widely used in smart wearable devices and smart phones due to their small size, stable performance, high signal-to-noise ratio, good sensitivity, and fast response speed.

After a long period of development, the performance indicators of audio chips are now more focused on intelligence, digitization and miniaturization. Today, MEMS audio chip technology is increasingly integrated with aerospace, biomedicine, consumer electronics, information communications and military industries, and higher requirements are placed on the performance of audio chips.

Summary of the invention

The present application provides an audio chip component based on a composite piezoelectric film, which can solve the technical problem in the prior art that the performance of the audio chip component needs to be further improved.

In a first aspect, the present application provides an audio chip component based on a composite piezoelectric film, comprising a substrate and a lower electrode, a first piezoelectric layer, a middle electrode, a second piezoelectric layer and an upper electrode sequentially deposited on the substrate, wherein the first piezoelectric layer has a low dielectric constant and a low piezoelectric coefficient, and the second piezoelectric layer has a high dielectric constant and a high piezoelectric coefficient.

In combination with the first aspect, in one implementation, the material of the lower electrode and the upper electrode is Mo, Al or Cu.

In combination with the first aspect, in one implementation, the material of the first piezoelectric layer and the second piezoelectric layer is AlN, ScAlN, PZT or ZnO.

In combination with the first aspect, in one implementation, the structures of the first piezoelectric layer and the second piezoelectric layer are AlN\ScAlN, AlN\PZT, ScAlN\PZT, AlN\ScAlN\PZT or AlN\ScAlN\AlN.

In a second aspect, the present application provides a piezoelectric microphone, comprising a housing and an audio chip assembly based on the composite piezoelectric film as described above, which is disposed in the housing.

In combination with the second aspect, in one implementation, the housing includes an outer shell and a substrate, and the outer shell and the substrate are connected via conductive glue or solder paste.

In combination with the second aspect, in one implementation, the substrate is a PCB board.

In a third aspect, the present application provides a method for preparing the piezoelectric microphone as described above, comprising the following steps:

Silicon wafer is selected as substrate;

Depositing a silicon dioxide protective layer on the upper surface of the substrate;

Depositing a lower electrode, a first piezoelectric layer, a middle electrode, a second piezoelectric layer and an upper electrode in sequence on a substrate;

Pre-etching is performed by etching to sequentially etch the upper electrode, the second piezoelectric layer, the middle electrode, the first piezoelectric layer, the lower electrode and the protective layer;

The back of the substrate is etched to form a back cavity structure, thereby obtaining an audio chip component with a cantilever beam structure;

The audio chip assembly and the ASIC chip are packaged to obtain a piezoelectric microphone device.

In a fourth aspect, the present application provides a speaker comprising an audio chip assembly based on the composite piezoelectric film as described above.

In a fifth aspect, the present application provides a method for preparing the loudspeaker as described above, comprising the following steps:

SOI (Silicon-On-Insulator) wafer is used as the substrate;

depositing a lower electrode on the upper surface of the substrate;

Then, a first piezoelectric layer, a middle electrode, a second piezoelectric layer and an upper electrode are sequentially deposited on the lower electrode;

Pre-etching is performed by etching to pattern the upper electrode and lead out the lower electrode;

Etching the back of the substrate to form a back cavity structure to obtain an audio chip component;

The audio chip components are packaged to obtain a speaker device.

The beneficial effects brought by the technical solution provided by the embodiment of the present application include at least:

The audio chip assembly based on the composite piezoelectric film provided in the present application arranges and combines a piezoelectric layer with a low dielectric constant (low dielectric loss) and a low piezoelectric coefficient (poor piezoelectric performance) and a piezoelectric layer with a high dielectric constant (high dielectric loss) and a high piezoelectric coefficient (good piezoelectric performance) into a dual-chip or multi-chip structure according to actual conditions. The advantages of each piezoelectric layer are complementary, so that the piezoelectric film as a whole has good piezoelectric and dielectric properties, thereby making the acoustic transducer containing the audio chip assembly have better acoustic performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a longitudinal cross-sectional view of a composite piezoelectric film provided in an embodiment of the present application;

FIG2 is a longitudinal cross-sectional view of a device after a silicon dioxide substrate, a lower electrode, a composite piezoelectric film, and an upper electrode are sequentially deposited on a bottom provided in Example 1 of the present application;

FIG3 is a longitudinal cross-sectional view of the device after the diaphragm is etched provided in Example 1 of the present application;

FIG4 is a longitudinal cross-sectional view of a device after back cavity etching provided in Example 1 of the present application;

FIG5 is a longitudinal cross-sectional view of the piezoelectric microphone diaphragm prepared in Comparative Example 1;

FIG6 is a longitudinal cross-sectional view of the piezoelectric microphone after packaging according to an embodiment of the present application;

FIG7 is a comparison diagram of microphone output voltages obtained in Example 1 of the present application and Comparative Example 1;

FIG8 is a longitudinal cross-sectional view of the device after sequentially depositing a lower electrode, a composite piezoelectric layer, and an upper electrode and etching according to Example 2 of the present application;

FIG9 is a longitudinal cross-sectional view of the device after back cavity etching in Example 2 of the present application;

FIG10 is a longitudinal cross-sectional view of the device prepared in Comparative Example 2;

FIG. 11 is a comparison chart of the output sound pressure levels of the loudspeakers prepared in Example 2 of the present application and Comparative Example 2 at a distance of 10 mm.

In the figure, 1, substrate; 2, protective layer; 3, lower electrode; 4, first piezoelectric layer; 5, second piezoelectric layer; 6, back cavity; 11, acoustic hole; 15, SOI wafer; 21, housing; 31, wire; 41, MEMS chip; 51, substrate; 61, ASIC chip.

Detailed ways

In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit the "first", "second" and "third" to different types.

In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

In the description of the embodiments of the present application, unless otherwise specified, “/” means or. For example, A/B can mean A or B. The “and/or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and/or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

In some processes described in the embodiments of the present application, multiple operations or steps that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

In order to make the objectives, technical solutions and advantages of the present application more clear, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

The present application provides an audio chip component based on a composite piezoelectric film, comprising a substrate 1 and a lower electrode 3, a first piezoelectric layer 4, a middle electrode, a second piezoelectric layer 5 and an upper electrode deposited layer by layer on the substrate 1, wherein the first piezoelectric layer 4 has a low dielectric constant and a low piezoelectric coefficient, and the second piezoelectric layer 5 has a high dielectric constant and a high piezoelectric coefficient.

The audio chip assembly based on the composite piezoelectric film provided in the present application arranges and combines a piezoelectric layer with a low dielectric constant (low dielectric loss) and a low piezoelectric coefficient (poor piezoelectric performance) and a piezoelectric layer with a high dielectric constant (high dielectric loss) and a high piezoelectric coefficient (good piezoelectric performance) into a dual-chip or multi-chip structure according to actual conditions. The advantages of each piezoelectric layer are complementary, so that the piezoelectric film as a whole has good piezoelectric and dielectric properties, thereby making the acoustic transducer containing the audio chip assembly have better acoustic performance.

In one embodiment, the electrode material of the lower electrode 3 and the upper electrode is any one of Mo, Al, Cu or other conductive materials.

In one embodiment, the material of the first piezoelectric layer 4 and the second piezoelectric layer 5 is any one of AlN, ScAlN, PZT, ZnO or other piezoelectric materials.

In one embodiment, the composite structure of the first piezoelectric layer 4 and the second piezoelectric layer 5 is any one of AlN\ScAlN, AlN\PZT, ScAlN\PZT, AlN\ScAlN\PZT, AlN\ScAlN\AlN or a multilayer composite structure composed of other piezoelectric layers with high piezoelectric coefficient and high dielectric constant, and piezoelectric layers with low dielectric coefficient and low dielectric constant.

Based on the same inventive concept, the present application also provides an acoustic transducer comprising an audio chip assembly based on the composite piezoelectric film as described above.

In a more specific embodiment, the acoustic transducer is a piezoelectric microphone, and the audio chip component is a cantilever beam of a MEMS chip 41 of the piezoelectric microphone. More specifically, the piezoelectric microphone includes a housing and a MEMS chip 41, the housing has a receiving cavity, the housing 21 is provided with a sound hole 11 communicating with the receiving cavity, and the MEMS chip 41 is received in the receiving cavity.

In a more specific embodiment, the housing includes an outer shell 21 and a substrate 51 , and the outer shell 21 and the substrate 51 enclose a containing cavity.

In a more specific embodiment, the MEMS chip 41 includes a fixed column and a cantilever beam, the fixed column is fixedly supported on the substrate 51, the fixed column is used to support the cantilever beam on the substrate 51, the number of the cantilever beams is multiple, the number of the fixed columns corresponds to the number of the cantilever beams, and there is a gap between two adjacent cantilever beams. The fixed base and the cantilever beam are continuous curved surface figures or polygons. More specifically, multiple cantilever beams are arranged in pairs, and the two cantilever beams in each pair are arranged facing each other. More specifically, the end of the cantilever beam that contacts and fixes with the fixed column is a fixed end, and the end away from the fixed column forms a free end.

In one embodiment, the cantilever beam is a bimorph structure, and the multilayer structure from bottom to top is: substrate 1, lower electrode 3, first piezoelectric layer 4, middle electrode, second piezoelectric layer 5 and upper electrode. The first piezoelectric layer 4 has a low dielectric constant and a low piezoelectric coefficient, and the second piezoelectric layer 5 has a high dielectric constant and a high piezoelectric coefficient.

In one embodiment, the fixing column is made of silicon or sapphire.

In one embodiment, the substrate 51 is a PCB board.

In one embodiment, the piezoelectric microphone further includes an ASIC chip 61 , and the ASIC chip 61 is electrically connected to the MEMS chip 41 via a wire 31 .

The longitudinal cross-sectional view of the composite piezoelectric film provided in the present application is shown in FIG1 , in which the middle electrode between the first piezoelectric layer 4 and the second piezoelectric layer 5 is omitted.

Based on the same inventive concept, the present application also provides a method for preparing the piezoelectric microphone as described above, comprising the following steps:

Step S1, selecting a silicon wafer as the substrate 1 of the cantilever beam;

Step S2, depositing a silicon dioxide protective layer 2 on the upper surface of the silicon wafer, and grinding the surface flat using a chemical mechanical polishing process;

Step S3, depositing the lower electrode 3, the first piezoelectric layer 4, the middle electrode, the second piezoelectric layer 5 and the upper electrode on the upper surface of the substrate 1 in sequence, and grinding the surface flat using a chemical mechanical polishing process, as shown in FIG2 ;

Step S4, pre-etching by etching, sequentially etching through the upper electrode layer, the piezoelectric layer, the middle electrode, the piezoelectric layer, the lower electrode 3 layers and the protective layer 2, as shown in FIG3 ;

Step S5, etching the back of the substrate 1 to form a back cavity 6 structure, and obtaining a cantilever beam diaphragm, as shown in FIG4 ; fixing the fixed end of the cantilever beam on the fixed column, and fixing the fixed column on the substrate 51 to form a MEMS chip 41;

Step S6: The MEMS chip 41 and the ASIC chip 61 are electrically connected and then packaged to obtain a piezoelectric microphone device, as shown in FIG. 6 .

In a more specific embodiment, the acoustic transducer is a speaker, and the above-mentioned audio chip component based on composite piezoelectric film is implemented as a diaphragm of the speaker, and the diaphragm includes a substrate 1, a lower electrode 3, a first piezoelectric layer 4, a middle electrode, a second piezoelectric layer 5 and an upper electrode from bottom to top; more specifically, the substrate 1 is an SOI substrate 1; more specifically, the first piezoelectric layer 4 has a low dielectric constant and a low piezoelectric coefficient, and the second piezoelectric layer 5 has a high dielectric constant and a high piezoelectric coefficient.

Based on the same inventive concept, the present application also provides a method for preparing the loudspeaker as described above, comprising the following steps:

Step S1, selecting an SOI wafer 15 as a substrate 1;

Step S2, depositing the lower electrode 3 on the upper surface of the substrate 1, and grinding the surface flat using a chemical mechanical polishing process;

Step S3, depositing the first piezoelectric layer 4, the middle electrode, the second piezoelectric layer 5 and the upper electrode on the upper surface of the lower electrode 3 in sequence, and grinding the surface flat using a chemical mechanical polishing process, as shown in FIG8 ;

Step S4, pre-etching by etching to pattern the upper electrode and lead out the lower electrode 3;

Step S5, etching the back of the substrate 1 to form a back cavity 6 structure, and manufacturing a diaphragm, as shown in FIG9 ;

Step S6: encapsulate the diaphragm to obtain a speaker device.

Example 1

A piezoelectric microphone device prepared based on the above method;

Example 2

A loudspeaker device prepared based on the above method;

Comparative Example 1

The structure of the piezoelectric microphone device is similar to that of Example 1, except that the diaphragm is a composite piezoelectric film design with one piezoelectric layer instead of two piezoelectric layers. The longitudinal cross-section of the device is shown in FIG5 .

FIG7 shows a comparison of the output voltage measurements of Example 1 and Comparative Example 1, and it can be seen that Example 1 has a larger output voltage. This is because the piezoelectric layer of Example 1 is a composite piezoelectric film composed of a piezoelectric layer with a low dielectric constant (low dielectric loss) and a low piezoelectric coefficient (poor piezoelectric performance) and a piezoelectric layer with a high dielectric constant (high dielectric loss) and a high piezoelectric coefficient (good piezoelectric performance). The film has good piezoelectric and dielectric properties as a whole, and can improve the output voltage of the piezoelectric microphone.

Comparative Example 2

The structure of the loudspeaker device is similar to that of Example 2, except that the diaphragm is a composite piezoelectric film design with one piezoelectric layer instead of two piezoelectric layers. The longitudinal cross-section of the device is shown in FIG10 .

Figure 11 shows a comparison of the output sound pressure level measurements of the loudspeakers prepared in Example 2 and Comparative Example 2. It can be seen that the loudspeaker device prepared in Example 2 has a larger output sound pressure level. This is because the piezoelectric layer of Example 2 is a composite piezoelectric film composed of a piezoelectric layer with a low dielectric constant (low dielectric loss) and a low piezoelectric coefficient (poor piezoelectric performance) and a piezoelectric layer with a high dielectric constant (high dielectric loss) and a high piezoelectric coefficient (good piezoelectric performance). The film has good piezoelectric and dielectric properties as a whole and can improve the output sound pressure level of the speaker.

In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise expressly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application will be understood according to the specific circumstances.

It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied for herein.

Claims (10)

1. The audio chip assembly based on the composite piezoelectric film is characterized by comprising a substrate, and a lower electrode, a first piezoelectric layer, a middle electrode, a second piezoelectric layer and an upper electrode which are sequentially deposited on the substrate, wherein the first piezoelectric layer has a low dielectric constant and a high piezoelectric coefficient, and the second piezoelectric layer has a high dielectric constant and a high piezoelectric coefficient.

2. The composite piezoelectric film-based audio chip assembly of claim 1, wherein the material of the lower electrode and the upper electrode is Mo, al, or Cu.

3. The composite piezoelectric film based audio chip assembly of claim 1, wherein the material of the first piezoelectric layer and the second piezoelectric layer is AlN, scAlN, PZT or ZnO.

4. The composite piezoelectric film-based audio chip assembly of claim 1, wherein the first piezoelectric layer and the second piezoelectric layer are structured of aln\scaln, aln\pzt, scaln\pzt, aln\ ScAlN \pzt, or aln\ ScAlN \aln.

5. A piezoelectric microphone comprising a housing and an audio chip assembly based on a composite piezoelectric film according to any one of claims 1-4 disposed within the housing.

6. The piezoelectric microphone of claim 5, wherein the housing comprises a shell and a substrate, the shell and the substrate being connected by conductive paste or solder paste.

7. The piezoelectric microphone of claim 6, wherein the substrate is a PCB board.

8. A method of manufacturing a piezoelectric microphone according to claim 5, comprising the steps of:

Selecting a silicon wafer as a substrate;

Depositing a silicon dioxide protective layer on the upper surface of the substrate;

sequentially depositing a lower electrode, a first piezoelectric layer, a middle electrode, a second piezoelectric layer and an upper electrode on a substrate;

Pre-etching in an etching mode, namely sequentially etching through the upper electrode, the second piezoelectric layer, the middle electrode, the first piezoelectric layer, the lower electrode and the protective layer;

Etching the back of the substrate to form a back cavity structure to obtain an audio chip assembly with a cantilever structure;

And packaging the audio chip assembly and the ASIC chip to obtain the piezoelectric microphone device.

9. A loudspeaker comprising an audio chip assembly based on a composite piezoelectric film as claimed in any one of claims 1 to 4.

10. A method of manufacturing a loudspeaker according to claim 9, comprising the steps of:

Selecting an SOI wafer as a substrate;

depositing a lower electrode on the upper surface of the substrate;

sequentially depositing a first piezoelectric layer, a middle electrode, a second piezoelectric layer and an upper electrode on the lower electrode;

Pre-etching in an etching mode to pattern the upper electrode and lead out the lower electrode;

etching the back of the substrate to form a back cavity structure, and preparing an audio chip assembly;

And packaging the audio chip assembly to obtain the loudspeaker device.