WO2022006817A1

WO2022006817A1 - Mems loudspeaker and manufacturing method therefor

Info

Publication number: WO2022006817A1
Application number: PCT/CN2020/101095
Authority: WO
Inventors: 张孟伦; 庞慰; 王昭勋
Original assignee: 诺思(天津)微系统有限责任公司
Priority date: 2020-07-09
Filing date: 2020-07-09
Publication date: 2022-01-13

Abstract

Disclosed is an MEMS loudspeaker. The MEMS loudspeaker is provided with an upper bottom surface and a lower bottom surface which are parallel to each other, a side wall is arranged therebetween, and a vibration direction of an actuator in the loudspeaker is parallel to the bottom surfaces; and the actuator has a plurality of branches, and the plurality of branches are arranged in one or more layers in the height direction of the loudspeaker. By using the technical solution of the present invention, the internal space of the loudspeaker can be fully used, the volume of air pushed by the the whole space of the loudspeaker is increased, and a sound pressure output of the loudspeaker is improved.

Description

MEMS speaker and method of making the same

technical field

The present invention relates to a MEMS speaker and a manufacturing method thereof.

Background technique

Micro-speakers are currently widely used in various miniaturized and miniaturized acoustic devices and electronic equipment, and are used in multimedia and electronic entertainment equipment. The MEMS (Micro Electro Mechanical System) actuator is an important part of the above speaker, and its core working principle is to use piezoelectric materials to realize the coupling and mutual conversion of acoustic energy (mechanical energy) and electrical energy. 1A and 1B are schematic diagrams of the structure of a MEMS speaker according to the prior art, wherein the actuator 2 of the speaker is fixed on the housing 1, and the actuator 2 vibrates up and down in the Z-axis direction to generate Sound waves, the pore structure 3 allows the air to flow. FIG. 1C is a schematic perspective view of a MEMS speaker according to the prior art. It can be seen that the speaker is a flat box in appearance.

At present, the miniaturization/miniaturization of speakers is one of the concerns in the industry. Due to the small size, the improvement of speaker performance (such as output sound pressure) is restricted to a certain extent. How to optimize the internal structure of the loudspeaker in a small size/small space is a key factor affecting the performance of the miniature loudspeaker.

SUMMARY OF THE INVENTION

In view of this, the present invention proposes a MEMS speaker and a manufacturing method thereof. The MEMS speaker has a large output sound pressure.

According to one aspect of the present invention, a MEMS speaker is provided.

The MEMS speaker of the present invention has an upper bottom surface and a lower bottom surface that are parallel to each other, with side walls therebetween, and the vibration direction of the actuator in the speaker is parallel to the bottom surface; Each of the branches is arranged in one or more layers in the height direction of the speaker.

Optionally, the shape of the speaker housing is a cuboid; each actuator branch is parallel to each other, one end of the actuator branch is connected to a set of opposite side walls of the speaker housing, and the other end of each actuator branch is a free end.

Optionally, the shape of the speaker housing is a rectangular parallelepiped; each actuator branch is parallel to each other, and both ends are respectively connected to a set of opposite side walls of the speaker housing.

Optionally, the shape of the speaker housing is a cuboid; each actuator branch is parallel to each other, one end is connected to one side wall of the speaker housing, and the other end is spaced from the opposite side wall of the side wall.

Optionally, the loudspeaker housing is in the shape of a cuboid; each actuator branch is parallel to each other; it also includes a load plate parallel to the actuator branch, and a connection part is provided between the load plate and the end of the actuator; the end of the load plate is connected with a connection column, The connecting post is connected to the upper bottom surface and/or the lower bottom surface of the casing of the speaker.

Optionally, the speaker further has a middle wall inside; one side or both sides of the middle wall is connected with the branches of the actuator.

Optionally, the connection part of the actuator branch is one of the following: the connection part is S-shaped; the connection part has the same shape as the actuator branch, but is thinner than the actuator branch; the connection part has 2 branches , the two branches and the side wall form a triangular prism.

Optionally, it also includes a load plate parallel to the branch of the actuator, and there is a connection portion between the load plate and the free end of the actuator.

Optionally, the load plate is divided into two parts, and the connection part is S-shaped and connected to the end of the load plate close to the actuator branch and to the end of the actuator branch.

Optionally, the load plate is divided into two parts, the connecting part is located between the end of the load plate and the end of the actuator; the end of the load plate is connected with a connecting column, and the connecting column is connected to the speaker the upper and/or lower underside of the enclosure.

Optionally, a plurality of partitions are arranged in the casing of the speaker, so that a plurality of independent spaces are formed in the casing.

Optionally, the actuator branch has a curved shape.

Optionally, the shape of the speaker housing is a rectangular parallelepiped; the branches of each actuator are parallel to each other, and have at least two of the following: a set of opposite side walls of the speaker housing are connected with one end of the branch of the actuator, and the branch of each branch of the actuator is connected. The other end is the free end, the actuator connected to one side wall is the same length as the actuator connected to the other side wall; a set of opposite side walls of the speaker housing is connected to one end of the branch of the actuator, and the branch of each branch of the actuator is connected. The other end is a free end, and the length of the actuator connected to one side wall is different from that of the actuator connected to the other side wall; both ends of each actuator branch are respectively connected to a set of opposite side walls of the speaker housing; each actuator One end of the branch is connected to one side wall of the speaker housing, and the other end is spaced from the opposite side wall of the side wall.

Optionally, the upper bottom surface and/or the lower bottom surface of the speaker housing has strip-shaped apertures.

Optionally, the upper bottom surface and the lower bottom surface of the speaker housing have strip-shaped holes, and the holes on the upper bottom surface and the holes on the lower bottom surface are staggered in the horizontal direction.

Optionally, one or more partitions are included in the speaker housing, so that the housing is divided into a plurality of independent spaces.

Optionally, the section of the actuator branch is trapezoidal.

Optionally, the base angle of the trapezoid is between 70° and 90°.

Optionally, a plurality of the branches are arranged in two layers in the height direction of the speaker, with a sacrificial layer between the two layers.

Optionally, a plurality of the branches are arranged in more than two layers in the height direction of the speaker, with gaps between adjacent layers.

According to another aspect of the present invention, there is provided a first method of manufacturing a MEMS speaker for manufacturing the above-mentioned MEMS speaker, the method comprising: preparing a 3-layer material having a top silicon, a bottom silicon and a sacrificial layer therebetween ; Etch the support layer of the top actuator branch and the speaker side wall on the top silicon; On the support layer of the top actuator branch, make the bottom electrode layer, the piezoelectric layer, and the top electrode layer; Bond the silicon chip to the top The top of the silicon is used as a bottom surface of the speaker; the device is turned over so that the bottom silicon is on the top; the support layer of the bottom actuator branch and the speaker side wall are etched on the bottom silicon; on the support layer of the bottom actuator branch, The bottom electrode layer, the piezoelectric layer, and the top electrode layer are made; the sacrificial layer is released except for the position between the upper and lower adjacent actuator branches; the silicon chip is bonded to the top of the bottom silicon as another bottom surface of the speaker.

According to yet another aspect of the present invention, a second method for manufacturing a MEMS speaker is provided for manufacturing the above-mentioned MEMS speaker, the method comprising: preparing a 3-layer material having a top silicon, a bottom silicon and a sacrificial layer therebetween ; Etch the support layer of the top actuator branch and the speaker side wall on the top silicon; On the support layer of the top actuator branch, make the bottom electrode layer; Make the piezoelectric layer on the bottom electrode layer; Make the top key on the top silicon The silicon wafer is bonded, the device is then turned over so that the bottom silicon is on top, and the silicon wafer is removed; the piezoelectric layer is continued to be formed on the bottom electrode layer; the top electrode is formed on the piezoelectric layer; and the silicon wafer is bonded on top of the bottom silicon.

According to yet another aspect of the present invention, a third method for manufacturing a MEMS speaker is provided for manufacturing the above-mentioned MEMS speaker, the method comprising: Step 1: preparing a MEMS speaker having a top silicon, a bottom silicon and a sacrificial layer therebetween 3 layers of materials; Step 2: Etch the support layer of the top actuator branch and the speaker sidewall on the top silicon; Step 3: On the support layer of the actuator branch, fabricate the bottom electrode layer, the piezoelectric layer, and the top electrode step 4: remove the bottom silicon layer, and then bond to the silicon wafer with silicon substrate as the first layer of actuator branches; step 5: superimpose one or more layers of single-layer actuator branches to all On the first-layer actuator, the single-layer actuator is fabricated by performing the steps 1 to 3 and removing the bottom silicon layer and the sacrificial layer; step 6: bonding silicon over the top actuator branch piece.

According to the technical solution of the embodiment of the present invention, when the actuator is arranged in the speaker housing, the vibration direction of the actuator is parallel to the bottom surface of the housing, which can make more full use of the internal space of the speaker and help improve the overall space of the speaker to push the air. volume, increasing the sound pressure output of the speaker.

Description of drawings

For purposes of illustration and not limitation, the present invention will now be described in accordance with preferred embodiments thereof, particularly with reference to the accompanying drawings, wherein:

1A and 1B are schematic diagrams of the structure of a MEMS speaker according to the prior art;

1C is a schematic perspective view of a MEMS speaker according to the prior art;

FIG. 2 is a three view of a MEMS speaker according to an embodiment of the present invention;

3 is a schematic perspective view of the structure of a MEMS speaker according to an embodiment of the present invention;

Figures 4 and 5 are schematic views of the locations of pore structures according to embodiments of the present invention;

6A and 6B are schematic diagrams of a MEMS speaker with an intermediate wall according to an embodiment of the present invention;

7 is a schematic diagram of the structure of another MEMS speaker according to an embodiment of the present invention;

8A to 8D are schematic diagrams illustrating the connection relationship between the actuator branch and the side wall of the speaker housing according to an embodiment of the present invention;

9A to 9D are schematic diagrams of the structure of the connecting portion of the actuator according to the embodiment of the present invention;

10A to 10D are schematic diagrams of a plate displacement increasing structure according to an embodiment of the present invention;

FIG. 11 is a schematic diagram of a MEMS speaker with an interior intermediate wall according to an embodiment of the present invention;

12 is a schematic diagram of a curved actuator branch according to an embodiment of the present invention;

13A-13G are schematic diagrams of a manufacturing process of a typical MEMS speaker according to an embodiment of the present invention;

14A to 14I are schematic diagrams of a processing flow of a double-layer actuator according to an embodiment of the present invention;

15A to 15K are schematic diagrams of a processing flow of an actuator according to an embodiment of the present invention;

16A to 16F are schematic diagrams of a processing flow of another actuator according to an embodiment of the present invention;

17A to 17F are schematic diagrams of a processing flow of a three-layer actuator according to an embodiment of the present invention.

detailed description

In the embodiment of the present invention, the posture of the actuator is changed so that its vibration direction is along the XY plane. Please refer to FIG. 2 for details. FIG. 2 is a three-view diagram of a MEMS speaker according to an embodiment of the present invention, wherein a partial magnification is also shown. picture.

In Figure 2, 1 is a speaker housing, which protects the internal piezoelectric driver structure and serves as a physical/electrical connection between the drivers. The loudspeaker housing may be a flat cuboid, ie the length and width dimensions are significantly larger than the height. The plane defined by the length and the width is the upper and lower bottom surfaces, and the side walls perpendicular to the bottom surface are between the upper and lower bottom surfaces. As an example, the size (length×width×height) of the entire speaker may be between 0.5mm×0.5mm×0.1mm to 20mm×20mm×1mm. 3 is the pore structure, so that the air inside the speaker can enter/exhaust with the vibration of the actuator, and the sound pressure can be increased to a certain extent through the specific opening position. Of course, the loudspeaker housing can also be a flat cylinder, that is, the size of the diameter of the bottom surface is significantly larger than the height.

2 is the actuator branch, which realizes the mutual conversion between electric energy and sound energy in the speaker. Because all the actuator branches are controlled uniformly, in the description of this paper, it is considered that the speaker housing contains one actuator, and the actuator has multiple branches. The actuator can convert the input electrical signal (electrical energy) into mechanical vibration (sound energy). Usually the length of the actuator branch is 0.5mm-10mm, the width is 0.1mm-1mm, and the thickness is 2um-30um. The figure also shows an optional internal structure of the actuator branch in a partially enlarged manner. In this structure, as shown in the figure, 4 is the electrode layer, which provides electrical connection for the actuator; 5 is the piezoelectric layer , convert the electrical signal into the mechanical vibration of the actuator; 6 is the support layer, which provides support for other parts of the actuator.

It can be seen from Figure 2 that the amplitude direction of the actuator branch is located in the XY plane, that is, the vibration direction of the actuator is parallel to the bottom surface of the speaker housing. In this way, the space in the speaker housing can be used more effectively, the actuator branches can be arranged more densely (compared with Fig. 1), more actuator branches can be accommodated, and the output sound pressure of the speaker can be improved. Referring to FIG. 3 , FIG. 3 is a schematic perspective view of the structure of a MEMS speaker according to an embodiment of the present invention. FIG. 3 shows a plurality of actuator branches 2 within the loudspeaker housing 1 , which have a porous structure 3 on their upper surface. 4 and 5 are schematic diagrams of the location of pore structures according to embodiments of the present invention. In Figure 3, the pore structure is opened on the upper bottom surface, and it can also be opened on the lower bottom surface. Alternatively, pore structures can be provided on the upper and lower bottom surfaces at the same time (as shown in FIG. 4 ), and the pores on the upper and lower bottom surfaces can also be staggered on the XY plane (as shown in FIG. 5 , which shows a view of the ZY plane). The holes can increase the amount of air entering the speaker, so that the volume of the air being pushed is larger, which helps to increase the output sound pressure of the speaker. The staggered arrangement of the pores in Figure 5 helps to make the air flow direction of the upper and lower speakers through the pore structure consistent, and try to avoid the mutual interference of the air between adjacent pores, thereby helping to improve the output sound pressure level.

One or more partitions may also be provided in the housing of the MEMS speaker according to the embodiment of the present invention. As shown in FIG. 5 , there are

partitions

51 and 52 between the actuator branches 2 , so that the housing contains multiple independent spaces. The figure is for illustration only, and the number of actuator branches between each partition can be flexibly selected in implementation. In the case of separators, there can still be a pore structure on the shell. The diaphragm creates a relatively closed space between the actuators and guides the air to flow from the appropriate pore structure; for the structure without diaphragm, if the actuator breaks and other mechanical damage, it will affect the work of other actuators in the speaker, and even cause the speaker Can not work, the introduction of the baffle structure can protect other actuators to continue to work when some actuators are damaged, increasing the reliability of the equipment.

In the above structure, there are 1 layer of actuator branches in the height direction, and it can also be multi-layer, as shown in FIG. 6A and FIG. 6B , FIG. 6A and FIG. Schematic diagram of the structure of the actuator branched MEMS speaker. Fig. 6A shows a top view of the XY plane, wherein the actuator branch in the housing 1 has upper and lower layers, namely the actuator branch 621 and the actuator branch 622, with a sacrificial layer 61 in the middle. As also shown in FIG. 7 , FIG. 7 is a schematic diagram of the structure of another MEMS speaker with multi-layer actuator branches according to an embodiment of the present invention, wherein the actuator branches 70 are provided with three layers in the height direction of the speaker housing 71 . There is space between each of the three layers, which is different from the case of two layers. The manufacturing methods of the above-mentioned two structures will be described later.

8A to 8D are schematic diagrams illustrating the connection relationship between the actuator branch and the side wall of the speaker housing according to an embodiment of the present invention. 8A-8D are views in the XY plane where the actuator may be attached to one side wall or a set of opposing side walls. 8A is a double-sided plate center slit structure, wherein the slit 80 is located at the center of the entire plate, FIG. 8B is a non-slit structure, FIG. 8C is a single-sided plate structure, and FIG. 8D is a double-sided plate offset slit structure. Different actuator plate structure designs can obtain different acoustic frequency responses. Selecting two or more of these structures and arranging them according to certain rules can make the speakers obtain different frequency response curves.

9A to 9D are schematic views of the structure of the connecting portion of the actuator according to the embodiment of the present invention. The figures show the connections of the actuator branches to the side walls of the loudspeaker housing, and the form of these connections can also be applied to the connection of the actuator branches to the intermediate wall within the loudspeaker housing. Figure 9A shows the basic structure of the connection. Excessive restraint will limit the vibration amplitude of the actuator. Therefore, it is better to reduce the restraint between the actuator and the mechanical casing while ensuring the stability of the connection between the actuator and the casing. 9B is connected by a serpentine structure, and the connecting part 7 is serpentine; Figure 9C is a thinned connection, and the thickness of the connecting part 8 is less than the thickness of the actuator; Figure 9D is a triangular connection, and the connecting part 9 has two branches. It is enclosed in a triangle with the shell. In these three connection methods, the material of the connection part can only contain the support layer, so as to reduce the constraint.

The sound pressure of the speaker is positively related to the volume of the air pushed by the actuator. In order to obtain a larger mechanical displacement, so that the speaker can obtain a larger sound pressure, the actuator in the embodiment of the present invention can also be equipped with a load plate, as shown in Figure 10A to As shown in FIG. 10D , FIGS. 10A to 10D are schematic diagrams of a plate displacement increasing structure according to an embodiment of the present invention. In each figure, 108 is the load plate. When the actuator branch vibrates, it drives the entire load plate to vibrate, so as to obtain an air pushing amount equal to more than twice the air pushed by the simple actuator, which helps to generate greater sound pressure.

FIG. 10A shows that the end of the actuator branch 2 directly drives the load plate 101 to vibrate, but this will hinder the vibration of the actuator branch to a certain extent and reduce the vibration amplitude. The serpentine/U-shaped connection part 102 in FIG. 10B can be Reducing such obstruction to a certain extent, a larger amplitude is obtained compared to Figure 10A. 10C and FIG. 10D adopt a lever structure, a connecting column 103 is arranged in the speaker casing, one or both ends of which are connected to the bottom surface of the loudspeaker casing, one end of the load plate 101 is connected to the connecting column 103, and the actuator branch 2 is connected near the end. It can be seen that due to the considerable difference in the length of the load plate on both sides of the connection point between the actuator branch 2 and the load plate, when the actuator branch 2 vibrates, the load plate can amplify the displacement of the actuator many times to push more Multiple volumes of air for greater sound pressure.

In the above illustration, the actuator branches are arranged parallel to each other. In fact, the actuator branches in the embodiment of the present invention may not be parallel to each other. For example, as shown in FIG. 11 , FIG. 11 is a schematic diagram of a MEMS speaker with a middle wall inside according to an embodiment of the present invention. The middle wall here only means that there is a wall in the speaker housing, and it does not necessarily have to be located in the middle. For example, in FIG. 11 , there are a plurality of middle walls 121 extending from the four corners to the center inside the speaker, and the actuator branch 2 is connected to the middle wall 121. . It can be seen from the figure that on the one hand, the internal space of the housing can be used more flexibly, and on the other hand, the length of the actuator has a richer change, so that the speaker has a richer frequency response. Therefore, the number and position of the intermediate walls can be set flexibly.

In the above illustration, the actuator branches are in the shape of a straight plate. In fact, the actuator branch in the embodiment of the present invention may be in a curved shape, for example, as shown in FIG. 12 , which is a schematic diagram of a curved actuator branch according to an embodiment of the present invention. In FIG. 12 , the arc-shaped actuator branch 2 is fixed on the middle wall 131 . Correspondingly, the housing 1 has a circular shape, but of course it can also be an elliptical shape. Correspondingly, if a pore structure is provided, the pores 132 can also be arc-shaped. .

In addition, the speaker housing can be in various other shapes, such as triangles, polygons, and even concave polygons, so that the speaker device can better adapt to the device or system in which it is located in terms of space occupation and other factors.

The manufacturing process of the MEMS speaker in the embodiment of the present invention will be described below. In the following description, it will be explained in conjunction with the ZY plane, and for the sake of clarity, only the cross-section of a single actuator branch is shown. (See ZY plan view of Figure 2) Multiple actuator branches.

13A to 13G are schematic diagrams of a manufacturing process of a typical MEMS speaker according to an embodiment of the present invention. Each part of the figure is explained as follows:

20: Support layer, which supports the actuator. The material can be silicon, silicon dioxide, aluminum nitride, molybdenum, aluminum, gold and other metals, as well as Parylene, polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), polyimide (PI), photoresist and other organic materials.

21: Sacrificial layer, in order to prevent the actuator from touching the speaker housing and causing the speaker volume to decrease and the sound quality to deteriorate. At the same time, the sacrificial material is provided for the convenience of processing. According to different processes, the materials can be silicon, silicon dioxide, aluminum nitride, molybdenum, aluminum, gold and other metals, as well as Parylene, polyethylene terephthalate (PET), polyethylene terephthalate (PET) Siloxane (PDMS), polyimide (PI), photoresist and other organic materials.

22: Bottom electrode layer, the material can be molybdenum, aluminum, gold, tungsten, ruthenium and so on.

23: Piezoelectric layer, aluminum nitride, zinc oxide, and rare earth element doped versions of the above materials (such as scandium aluminum nitride with a certain atomic ratio), lead zirconate titanate, doped lead zirconate titanate, niobium Lithium oxide, lithium tantalate, polyvinylidene fluoride (pvdf), etc.

24: The top electrode layer can be selected from molybdenum, aluminum, gold, tungsten, ruthenium and so on.

A typical processing flow is as follows, and Figures 13A to 13G correspond to Step 1 to Step 7 respectively:

Step 1: Clean the silicon wafer (SOI) on the insulating substrate (the bottom silicon is the speaker housing, the top silicon is the support layer of the actuator, and the thickness of the top support layer usually determines the height of the actuator branch).

Step 2: Etch out the pattern of the actuator branches according to the requirements, and grow the bottom electrode layer.

Step 3: Etch the excess electrode material.

Step 4: Use the same method to grow the piezoelectric layer and top electrode layer and etch the excess material.

Step 5: Etch openings in the underlying silicon.

Step 6: Release the sacrificial layer (silicon dioxide).

Step 7: Bonding or adhering the etched silicon wafer with the pore structure to the overall structure.

The processing flow of the double-layer actuator is shown in FIGS. 14A to 14I , and FIGS. 14A to 14I are schematic diagrams of the processing flow of the double-layer actuator according to an embodiment of the present invention, and FIGS. 14A to 14I correspond to step A to step I respectively. :

Step A: Clean the silicon wafer (SOI) on the insulating substrate (the bottom silicon is the speaker shell, the top silicon is the support layer of the actuator branch, and the thickness of the top support layer usually determines the height of the actuator branch).

Step B: Etch the shape of the top actuator branch as required.

Step C: The bottom electrode layer, the piezoelectric layer and the top electrode layer are grown and patterned.

Step D: bonding the silicon with the etched opening structure to the device.

Step E: Rotate the device with the bottom as the top of the device.

Step F: Etch the other side out of the shape of the actuator branch.

Step G: The bottom electrode layer, the piezoelectric layer and the top electrode layer are grown and patterned.

Step H: Release the sacrificial layer (silicon dioxide).

Step I: bonding the silicon with the etched opening structure to the device.

Since the device has a large aspect ratio, the piezoelectric layer material may grow in a poor state, and usually more material will grow on the top, resulting in an inverted trapezoid growth of the piezoelectric layer. Therefore, the fabrication scheme shown in FIGS. 15A to 15K is adopted to solve this problem. 15A to 15K are schematic diagrams of a processing flow of an actuator according to an embodiment of the present invention, and FIGS. 15A to 15K correspond to steps A to K respectively:

Step B: Etch the shape of the top actuator branch as required.

Step C: Growing and patterning the bottom electrode layer.

Step D: Top Aluminum Nitride is grown and patterned.

Step E: Bond a silicon wafer on top.

Step F: Rotate the silicon wafer 180° with the bottom as the top of the device and remove the top silicon.

Step G: Aluminum nitride is grown again and patterned.

Step H: Growing the top electrode and patterning.

Step I: Etching an opening structure on the bottom silicon.

Step J: Release the sacrificial material.

Step K: bonding the silicon wafer with the opening structure.

In addition, because the device has a large aspect ratio, it is difficult to achieve an absolutely vertical angle. Therefore, in the embodiment of the present invention, the actuator can also be made into a trapezoid to reduce the difficulty of the process. When the inclination angle is between 70° and 90° At the same time, due to the change of the shape, the resonance of the device can be suppressed to a certain extent, and better device performance can be obtained. 16A to 16F are schematic diagrams of a processing flow of another actuator according to an embodiment of the present invention, and FIGS. 16A to 16F correspond to steps A to F respectively:

Step A: Clean the silicon wafer (SOI) on the insulating substrate (the bottom silicon is the speaker shell, the top silicon is the support layer of the actuator branch, and the thickness of the top support layer usually determines the height of the actuator branch). The pattern of the actuator branch is etched as required.

Step B: Growing the bottom electrode layer.

Step C: Etching excess electrode material.

Step D: Growing the Piezoelectric Layer and Patterning.

Step E: Growing the top electrode layer and patterning.

Step F: Release the sacrificial layer material.

In order to make the effective vibration space of the device larger, as mentioned above, a multi-layer stacking scheme is designed in the embodiment of the present invention. The processing method of this solution will be described below, taking a three-layer stacked structure as an example, as shown in FIGS. 17A to 17F . 17A to 17F correspond to steps A to F respectively:

Step A: Prepare three silicon wafers (SOI) on insulating substrates for cleaning (the bottom silicon is the speaker housing, and the top silicon is the support layer of the actuator. Usually, the thickness of the top support layer determines the height of the actuator branches).

Step B: Etch the shape of the top actuator branch as required.

Step D: Release the sacrificial layer and remove the bottom silicon layer. So far, the layer 1 actuator branch is completed. According to the required number of layers, the same other layer actuator branches are fabricated, that is, steps A to D are repeated, and the bottom silicon layer and sacrificial layer are removed after step D to obtain the single-layer actuator branch shown in FIG. 17D .

Step E: Bonding a plurality of single-layer actuator branches to a silicon wafer with a silicon substrate (3 layers are superimposed in the figure). Photoresist adhesives can be used for bonding and stacking.

Step F: Bonding a silicon wafer with an open-hole structure on the uppermost layer of the actuator branches.

The above-mentioned specific embodiments do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

A MEMS loudspeaker has an upper bottom surface and a lower bottom surface that are parallel to each other, and has a side wall between the two, characterized in that:

The vibration direction of the actuator in the speaker is parallel to its bottom surface;

The actuator has a plurality of branches, and the plurality of branches are arranged in one or more layers in the height direction of the speaker.
The MEMS speaker according to claim 1, wherein,

The shape of the speaker shell is a rectangular parallelepiped;

Each actuator branch is parallel to each other, a set of opposite side walls of the speaker housing are connected with one end of the actuator branch, and the other end of each actuator branch is a free end.
The MEMS speaker according to claim 1, wherein,

The shape of the speaker shell is a rectangular parallelepiped;

The actuator branches are parallel to each other, and the two ends are respectively connected to a set of opposite side walls of the speaker housing.
The MEMS speaker according to claim 1, wherein,

The shape of the speaker shell is a rectangular parallelepiped;

Each actuator branch is parallel to each other, one end is connected to one side wall of the speaker housing, and the other end is spaced from the opposite side wall of the side wall.
MEMS speaker according to claim 4, is characterized in that,

The shape of the speaker shell is a rectangular parallelepiped;

Each actuator branch is parallel to each other;

It also includes a load plate parallel to the actuator branch, and a connection portion is provided between the load plate and the end of the actuator;

A connecting column is connected to the end of the load plate, and the connecting column is connected to the upper bottom surface and/or the lower bottom surface of the casing of the loudspeaker.
The MEMS speaker according to claim 1, wherein,

The speaker also has a middle wall inside;

One or both sides of the intermediate wall are connected with branches of the actuator.
The MEMS speaker according to any one of claims 1 to 6, wherein the connecting portion of the actuator branch is one of the following:

The connecting portion is S-shaped;

The connecting portion has the same shape as the actuator branch, but is thinner than the actuator branch;

The connecting portion has two branches, and the two branches and the side wall form a triangular prism.
The MEMS speaker according to any one of claims 2 to 6, further comprising a load plate parallel to the branch of the actuator, and a connection portion is provided between the load plate and the free end of the actuator.
The MEMS speaker according to claim 8, wherein,

The load plate is divided into two parts, and the connection part is S-shaped and connected to the end of the load plate close to the actuator branch and to the end of the actuator branch.
The MEMS speaker according to claim 8, wherein,

The load plate is divided into two parts, and the connection part is located between the end of the load plate and the end of the actuator;

A connecting column is connected to the end of the load plate, and the connecting column is connected to the upper bottom surface and/or the lower bottom surface of the casing of the loudspeaker.
The MEMS speaker according to claim 1, wherein a plurality of partitions are arranged in the casing of the loudspeaker, so that a plurality of independent spaces are formed in the casing.
The MEMS speaker of claim 1, wherein the actuator branch is in a curved shape.
The MEMS speaker according to claim 1, wherein,

The shape of the speaker shell is a rectangular parallelepiped;

The branches of each actuator are parallel to each other and have at least two of the following:

A set of opposite side walls of the speaker housing are connected with one end of the branch of the actuator, the other end of each actuator branch is a free end, the length of the actuator connected on one side wall is the same as that of the actuator connected on the other side wall,

A set of opposite side walls of the speaker housing are connected with one end of the branch of the actuator, the other end of each actuator branch is a free end, the length of the actuator connected on one side wall is different from that of the actuator connected on the other side wall,

Both ends of each actuator branch are respectively connected to a set of opposite side walls of the speaker housing,

One end of each actuator branch is connected to one side wall of the speaker housing, and the other end is spaced from the opposite side wall of the side wall.
The MEMS speaker according to claim 1, characterized in that, the upper bottom surface and/or the lower bottom surface of the speaker housing has strip-shaped apertures.
The MEMS speaker according to claim 4, wherein the upper bottom surface and the lower bottom surface of the speaker housing have strip-shaped holes, and the holes on the upper bottom surface and the holes on the lower bottom surface are staggered in a horizontal direction.
The MEMS loudspeaker according to claim 1 or 14, wherein the loudspeaker casing includes one or more partitions, so that the casing is divided into a plurality of independent spaces.
The MEMS speaker according to claim 1, wherein the cross section of the actuator branch is a trapezoid.
The MEMS speaker according to claim 17, wherein the base angle of the trapezoid is between 70° and 90°.
The MEMS speaker according to claim 1, wherein a plurality of the branches are arranged in two layers in the height direction of the speaker, with a sacrificial layer between the two layers.
The MEMS speaker according to claim 1, wherein a plurality of the branches are arranged in more than two layers in the height direction of the speaker, with gaps between adjacent layers.
A method for manufacturing a MEMS speaker for manufacturing the MEMS speaker according to claim 19, wherein the method comprises:

Prepare a 3-layer material with top silicon, bottom silicon, and a sacrificial layer in between;

Etch the support layer and speaker side wall of the top actuator branch on the top silicon;

On the support layer of the top actuator branch, a bottom electrode layer, a piezoelectric layer, and a top electrode layer are fabricated;

bonding the silicon chip to the top of the top silicon as a bottom surface of the speaker;

Flip the device so that the bottom silicon is on top;

Etch the support layer of the bottom actuator branch and the speaker side wall on the bottom silicon;

On the support layer of the bottom actuator branch, a bottom electrode layer, a piezoelectric layer, and a top electrode layer are fabricated;

Release the sacrificial layer except the position between the upper and lower adjacent actuator branches;

A silicon wafer is bonded to the top of the bottom silicon as the other bottom surface of the speaker.
A method for manufacturing a MEMS speaker for manufacturing the MEMS speaker according to claim 1, wherein the method comprises:

Prepare a 3-layer material with top silicon, bottom silicon, and a sacrificial layer in between;

Etch the support layer and speaker side wall of the top actuator branch on the top silicon;

On the support layer of the top actuator branch, make the bottom electrode layer;

making a piezoelectric layer on the bottom electrode layer;

Bonding a silicon wafer on top of the top silicon, then flipping the device so that the bottom silicon is on top, and removing the wafer;

Continue to make the piezoelectric layer on the bottom electrode layer;

make a top electrode on the piezoelectric layer;

Bond the silicon wafer on top of the bottom silicon.
A method for manufacturing a MEMS speaker for manufacturing the MEMS speaker according to claim 20, wherein the method comprises:

Step 1: Prepare a 3-layer material with top silicon, bottom silicon and a sacrificial layer in between;

Step 2: Etch the support layer of the top actuator branch and the speaker side wall on the top silicon;

Step 3: on the support layer of the actuator branch, make a bottom electrode layer, a piezoelectric layer, and a top electrode layer;

Step 4: Remove the silicon layer at the bottom, and then bond it to the silicon wafer with the silicon substrate as the first layer of actuator branches;

Step 5: One or more layers of single-layer actuator branches are superimposed and bonded to the first-layer actuator, and the single-layer actuator is fabricated by performing the steps 1 to 3 and removing the bottom a silicon layer and the sacrificial layer;

Step 6: Bond the silicon over the top actuator branch.