WO2022252178A1

WO2022252178A1 - Fin structure speaker and method for forming same

Info

Publication number: WO2022252178A1
Application number: PCT/CN2021/098112
Authority: WO
Inventors: 张孟伦
Original assignee: 天津大学
Priority date: 2021-06-03
Filing date: 2021-06-03
Publication date: 2022-12-08

Abstract

Disclosed are a fin structure speaker and a method for forming same. The fin structure speaker comprises a surrounding frame and a plurality of speaker fins located in the surrounding frame. Each speaker fin comprises: a fin substrate; and a piezoelectric layer that is non-uniform in thickness and located on the surfaces of two vertical sidewalls of the fin substrate. According to the technical solution of the present invention, the thickness of a piezoelectric layer material on the vertical sidewall of each fin structure of the fin speaker varies along the direction of the vertical sidewall of the fin (for example, in a wedge shape), and the specific thickness variation trend is that the thickness near the end of the speaker fin is thicker, and the thickness near the middle of the speaker fin is thinner. In this way, when the thickness of the piezoelectric layer varies along the extension direction of the vertical sidewall of the fin structure, the characteristics of large fin displacement and high displacement linearity can be met at the same time. On the other hand, since the thickness of the piezoelectric layer varies along the direction of the vertical sidewall of the fin structure, the resonance of the fin structure in a broadband can reduce the Q value and increase the bandwidth, thereby improving the frequency response of the speaker.

Description

Fin structure loudspeaker and its forming method

technical field

The invention relates to the technical field of MEMS (micro-electro-mechanical systems), in particular to a fin-structure loudspeaker and a forming method thereof.

Background technique

In recent years, the technical field of MEMS (Micro-Electro-Mechanical Systems) has achieved rapid development, and miniature fin-structured loudspeakers have appeared. The fin structure loudspeaker has the basic components as shown in Figure 1A, where C1 is the upper package cover structure, C2 is the lower package cover structure, and D1 is the core working area. Further, the top view structure of D1 is shown in FIG. 1B , the D1 structure includes a surrounding frame and several fins F1 to F8 (the number is 8 is just an example) located in the frame.

In prior art fin structure loudspeakers, the thickness of the piezoelectric layer is uniform. Assuming that the driving voltage remains unchanged, when the thickness of the piezoelectric layer is thicker, the electric field inside the piezoelectric layer is smaller, the fin displacement is smaller, and the sound pressure generated by the speaker is lower, which cannot meet the index requirements; when the thickness of the piezoelectric layer is thinner At this time, although the electric field inside the piezoelectric layer is relatively large, the output linearity of the speaker is poor due to the nonlinearity of the piezoelectric material. In addition, when the thickness of the piezoelectric layer is uniform, the Q value of the fins at mechanical resonance is high, resulting in poor frequency response and small bandwidth of the speaker.

Contents of the invention

In view of this, the present invention proposes a fin structure loudspeaker structure and a forming method thereof.

The first aspect of the present invention proposes a fin structure loudspeaker, including a surrounding frame and a plurality of sound-speaking fins located in the surrounding frame, and the sound-speaking fins include: a fin base; A piezoelectric layer of uneven thickness on the surface of the two vertical sidewalls.

Optionally, the material of the fin base is silicon.

Optionally, crystal phases of the piezoelectric layers on the surfaces of the two vertical sidewalls of the same fin base are opposite.

Optionally, the section of the piezoelectric layer is wedge-shaped.

Optionally, the piezoelectric layer has a maximum width at a position closest to the top and bottom of the speaker fin, and the piezoelectric layer has a minimum width at a position closest to the middle of the speaker fin; Alternatively, the piezoelectric layer has the largest width at a position closest to one of the top and bottom ends of the sounding fin, and the piezoelectric layer has the largest width at a position closest to the top and bottom of the sounding fin. The position of the other of the two ends has the minimum width.

Optionally, the angle between the outer surface of the piezoelectric layer and the vertical side wall surface of the fin base is defined as a first angle, and the first angle ranges from 0 to 45°.

Optionally, the ratio of the length of the piezoelectric layer covering the vertical sidewall of the fin base to the full length of the vertical sidewall of the fin base is defined as the piezoelectric layer coverage ratio, and the piezoelectric layer covers The ratio of the ratio ranges from 10% to 100%, or from 30% to 60%.

Optionally, the speaker fins further include: external electrodes located on the surface of the piezoelectric layer.

Optionally, an angle between the outer surface of the external electrode and the outer surface of the piezoelectric layer is defined as a second included angle, and the value of the second included angle ranges from 0 to 45°.

Optionally, the thickness of the piezoelectric layer under the ends of the external electrodes is greater than 100 nanometers.

Optionally, the coverage area of the external electrode is smaller than the coverage area of the piezoelectric layer.

Optionally, the speaker fin further includes: an internal electrode located between the fin base and the piezoelectric layer.

Optionally, the piezoelectric layers on both sides of the same speaker fin are powered independently.

Optionally, the piezoelectric layer material is: aluminum nitride, PZT, zinc oxide or a doped material of the above materials.

Optionally, the piezoelectric layer is in the form of a thin film with an average thickness of 0.1 microns to 10 microns.

Optionally, it also includes: an upper package cover structure located above the surrounding frame and the plurality of sound-speaking fins, and a lower package cover structure located below the surrounding frame and the plurality of sound-speaking fins, wherein , the upper package cover structure and/or the lower package cover structure has an acoustic hole.

The second aspect of the present invention provides a method for forming a fin structure loudspeaker, including: processing a wafer into a surrounding frame and a plurality of fin bases located in the surrounding frame; A piezoelectric layer with non-uniform thickness is formed on the surface of the wall, and the fin base and the piezoelectric layer constitute a sound-speaking fin.

Optionally, the material of the fin base is silicon.

Optionally, the section of the piezoelectric layer is wedge-shaped.

Optionally, the method further includes: forming external electrodes on the surface of the piezoelectric layer.

Optionally, the method further includes: forming an internal electrode between the fin base and the piezoelectric layer.

Optionally, the piezoelectric layers on both sides of the sound-speaking fins are powered independently.

Optionally, further comprising: encapsulating an upper encapsulation cover structure above the surrounding frame and the plurality of sound-speaking fins, and encapsulating a lower encapsulation cover structure below the surrounding frame and the plurality of sound-speaking fins , wherein the upper package cover structure and/or the lower package cover structure has an acoustic hole.

According to the technical solution of the present invention, the thickness of the piezoelectric layer material of the vertical side wall of each fin structure of the fin speaker changes along the direction of the vertical side wall of the fin (for example, it is wedge-shaped), and the specific thickness variation trend is close to the vertical side wall of the fin. The sound fins are thicker at the ends and thinner near the middle of the sound fins. In this way, when the thickness of the piezoelectric layer changes along the extending direction of the vertical side wall of the fin structure, the characteristics of large displacement and high linearity of displacement of the fin can be satisfied at the same time. On the other hand, since the thickness of the piezoelectric layer varies along the vertical sidewall direction of the fin structure, the fin structure resonates in a wide frequency range, which can reduce the Q value and increase the bandwidth, thereby improving the frequency response of the speaker.

Description of drawings

For purposes of illustration and not limitation, the invention will now be described according to its preferred embodiments, particularly with reference to the accompanying drawings, in which:

1A and 1B are schematic diagrams of the overall structure of a fin structure speaker;

2A to 2L are schematic diagrams of the forming process of the fin structure loudspeaker according to the embodiment of the present invention;

3 is a cross-sectional view of a single fin base according to an embodiment of the present invention;

FIG. 4 is a partially enlarged view of the R1 region in FIG. 3 .

Detailed ways

The technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, but not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention belong to the protection scope of the present invention.

The overall structure of the fin structure loudspeaker according to the embodiment of the present invention is also shown in FIG. 1A and FIG. 1B , but the thickness of the piezoelectric layer in the fin base is non-uniform. The processing flow of the fin structure loudspeaker according to the embodiment of the present invention will be introduced in detail below to illustrate the key features involved in the present invention. The cross-section is the S1 plane in FIG. 1A , and the number of sound-speaking fins is intentionally reduced for the sake of illustration.

Step 1: Process the wafer into a surrounding frame and several fin bases located in the surrounding frame.

(1) As shown in Figure 2A, the masks M1 and M2 are respectively covered on both sides of the wafer D1 by CVD or other processes. The material can be silicon dioxide, silicon nitride, aluminum nitride, etc., or a composite layer of the above materials. Here, ordinary silicon wafers are used instead of SOI silicon wafers, which can greatly reduce manufacturing costs.

(2) As shown in FIG. 2B , one side of the mask is patterned by dry or wet etching, and the patterned mask layer is M1 in this example. Here, for the convenience of display, the number of fin bases is reduced to 3 pieces, and accordingly, 4 exposure windows are set on the cross section of the mask M1.

(3) As shown in FIG. 2C , three fin bases are processed on D1 by wet process (potassium hydroxide solution etching, etc.) or dry process (DRIE, etc.). The processed fin gap between the fin bases runs through the wafer D1 and ends at the mask layer M2.

(4) As shown in FIG. 2D , the masks M1 and M2 are removed, and the wafer D1 with the fin base remains. At this time, the part of the periphery of the wafer becomes the surrounding frame in the fin structure speaker.

In fact, the above process is only an optional way to obtain the transparent fin base in FIG. 2D , and is not intended to be limiting. Other process flows can also be used to obtain the structure of Figure 2D.

Step 2: forming a piezoelectric layer with an uneven thickness on the surfaces of the two vertical side walls of the fin base, and the fin base and the piezoelectric layer form a speaker fin. Here, the vertical sidewall is the sidewall of the fin perpendicular to the base.

As shown in FIG. 2E, the piezoelectric layer film L1 is deposited on one side of the wafer D1, wherein the section of L1 located on the vertical side wall of the fin has a wedge shape or similar wedge shape, specifically, the wedge is near the wafer The portion of the surface of D1 has a large width and gradually becomes thinner as the depth increases. Optionally, a layer of protective layer material P1 may be bonded to the non-deposition side of D1 for protecting the cavity and devices during the deposition process. Then, as shown in FIG. 2F , a piezoelectric layer L2 is deposited on the opposite side of the deposited layer L1 (optionally, a protective layer P2 is used). Preferably, L2 and L1 have the same or similar cross-sectional structure and size distribution. In addition, there is a "lap" at the end of L1 and L2 deep into the wafer in this example, so that L1 and L2 are fused into one piezoelectric layer. In the non-overlapping part, the piezoelectric layer thickness varies with depth. The piezoelectric layer material includes aluminum nitride, PZT, zinc oxide, and doped materials of the above materials; the piezoelectric layer is in the form of a thin film with an average thickness of 0.1 micron to 10 micron.

The crystal phases of the piezoelectric layers on the surfaces of the two vertical sidewalls of the same fin base are opposite. This is beneficial to the stress symmetry of the piezoelectric layer on both sides of the same fin base.

In the method for forming a fin structure loudspeaker according to the embodiment of the present invention, between step 1 and step 2, a step may further be included: forming an internal electrode located between the fin base and the piezoelectric layer. The internal electrodes are not an essential structure. When the fin base is made of a material with low resistivity, the fin base can be directly used as the internal electrode.

The method for forming a fin structure loudspeaker according to the embodiment of the present invention may further include a step of forming an external electrode on the surface of the piezoelectric layer.

As shown in FIG. 2G , the metal layer E2 is continuously deposited on the side where L2 has been deposited as an electrode. E2 has a wedge-shaped structure on the vertical sidewall of the piezoelectric layer. Then, as shown in FIG. 2H , continue to deposit a metal layer E1 as an external electrode (optionally, use a protective layer P3 ) on the opposite side where the E2 layer has been deposited. The external electrode E2 has a wedge-shaped structure on the vertical sidewall of the piezoelectric layer. In this example, E2 and E1 have a "lap" at the end deep into the wafer to form a layer of metal electrodes.

The method for forming a fin structure loudspeaker according to the embodiment of the present invention may further include a step of: forming breaks in the external electrodes at both ends of the sound-speaking fins.

Specifically, as shown in FIG. 2I, the external electrodes that originally surround the piezoelectric layer are disconnected above the top end and the bottom end of each fin base through a process such as dry or wet etching, This enables independent power supply to the piezoelectric layers located on the two vertical sidewalls of each fin. Optionally, the metal located on the upper and lower surfaces of the D1 frame can also be removed for subsequent processes.

The method for forming the fin structure loudspeaker according to the embodiment of the present invention may further include a step of packaging the upper package cover structure and the lower package cover structure.

Specifically, as shown in FIG. 2J , the upper package lid structure C1 and the lower package lid structure C2 are respectively bonded on both sides of FIG. 2I , wherein V1-2 and U1-2 are acoustic holes located on C1 and C2. This step is a common process and is not the focus of this article, so specific steps are omitted.

As an example, in the above-mentioned structural process, an "overlap" is formed between the piezoelectric layers L1 and L2/between the electrodes E1 and E2 deep in the wafer D1. In addition, the above-mentioned electrodes and piezoelectric layers can also be formed on the vertical side walls. In the non-contact structure, as shown in FIG. 2K , on the two vertical sidewalls of each fin, there is an exposed wafer surface between the piezoelectric layers L1 and L2 / between the electrodes E1 and E2 .

In the method of forming a fin structure speaker in other embodiments of the present invention, as shown in FIG. 2L , only one side of the fin may cover the piezoelectric layer L1 and the electrode E1 .

As shown in FIG. 3, the wedge-shaped piezoelectric layer and external electrodes can be defined in shape and size. The angle between the outer surface of the piezoelectric layer and the side plane of the fin base is defined as a first angle α, and the value range of the first angle α is 0 to 45°. The angle between the outer surface of the external electrode and the outer surface of the piezoelectric layer is defined as a second angle β, and the value range of the second angle β is 0 to 45°. For a fin base whose vertical sidewall height (length) is H, the value of the covering height (length) h2 of the piezoelectric layer L1 on one side of the vertical sidewall is between 10% and 100% of H, preferably 30%. to 60%. In the case of an overlying piezoelectric layer, this requirement also applies to the other piezoelectric layer. In addition, the basic principle of the relative position of the end of the external electrode and the end of the piezoelectric layer is: the coverage area of the external electrode is smaller than the coverage area of the piezoelectric layer (so as to ensure that the external electrode will not cover the surface of the silicon-based fin), in other words, the external electrode in Figure 3 The dimension h1' is smaller than the dimension h2' of the piezoelectric layer, and the dimension h1 of the external electrode is smaller than the dimension h2 of the piezoelectric layer.

As shown in Figure 4 (Figure 4 is the enlarged area of R1 in Figure 3), the thickness D1 of the piezoelectric layer below the end of the external electrode is required to be greater than 100nm, so as to ensure that there is a sufficiently thick piezoelectric material between the electrode E1 and the silicon-based fin Fn Thereby achieving an insulating effect and preventing the piezoelectric layer from being electrically broken down.

In the fin-structure loudspeaker in other embodiments of the present invention, internal electrodes may also be provided between the piezoelectric layer and the fin base for better electrical connection. In this case, the resistivity of the material of the fin base is not required.

The above specific implementation methods do not constitute a limitation to the protection scope of the present invention. It should be apparent to 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 principles of the present invention shall be included within the protection scope of the present invention.

Claims

A fin structure loudspeaker is characterized in that it comprises a surrounding frame and a plurality of sound-speaking fins located in the surrounding frame, and the sound-speaking fins include:

fin base;

A piezoelectric layer with an uneven thickness located on the surfaces of the two vertical sidewalls of the fin base.
The fin structure loudspeaker according to claim 1, characterized in that the material of the fin base is silicon.
The loudspeaker with fin structure according to claim 1, characterized in that the crystal phases of the piezoelectric layers on the surfaces of the two vertical side walls of the same fin base are opposite.
The fin structure loudspeaker according to claim 1, wherein the section of the piezoelectric layer is wedge-shaped.
The fin structure loudspeaker according to claim 4, characterized in that,

The piezoelectric layer has a maximum width at a position closest to the top and bottom ends of the speaker fin, and the piezoelectric layer has a minimum width at a position closest to the middle of the speaker fin; or,

The piezoelectric layer has a maximum width at a position closest to one of the top end and the bottom end of the speaker fin, and the piezoelectric layer has a maximum width at a position closest to the top end and the bottom end of the speaker fin. The position of the other of the two has the minimum width.
The fin structure loudspeaker according to claim 4, wherein the angle between the outer surface of the piezoelectric layer and the vertical side wall surface of the fin base is defined as a first angle, and the first angle is Angle ranges from 0 to 45°.
The fin structure loudspeaker according to claim 4, wherein the ratio of the length of the piezoelectric layer covering the vertical side wall of the fin base to the full length of the vertical side wall of the fin base is defined as The coverage ratio of the piezoelectric layer, the ratio of the coverage ratio of the piezoelectric layer ranges from 10% to 100%, or from 30% to 60%.
The fin structure loudspeaker according to claim 1, wherein the sound speaker fin further comprises: an external electrode located on the surface of the piezoelectric layer.
The fin structure loudspeaker according to claim 8, wherein the angle between the outer surface of the external electrode and the outer surface of the piezoelectric layer is defined as a second angle, and the value of the second angle is The range is 0 to 45°.
The fin structure loudspeaker according to claim 8, characterized in that the thickness of the piezoelectric layer below the ends of the external electrodes is greater than 100 nanometers.
The fin structure loudspeaker according to claim 8, wherein the covering area of the outer electrode is smaller than the covering area of the piezoelectric layer.
The fin structure speaker according to claim 1, wherein the sound speaker fin further comprises: an internal electrode located between the fin base and the piezoelectric layer.
The fin-structure loudspeaker according to claim 1, wherein the piezoelectric layers on both sides of the same sound-speaking fin are powered independently.
The fin structure loudspeaker according to claim 1, wherein the piezoelectric layer material is: aluminum nitride, PZT, zinc oxide or a doped material of the above materials.
The fin structure loudspeaker according to claim 1, wherein the piezoelectric layer is in the form of a thin film with an average thickness of 0.1 microns to 10 microns.
The fin structure loudspeaker according to any one of claims 1 to 15, further comprising: an upper package cover structure located above the surrounding frame and the plurality of sound-speaking fins, and a structure located on the surrounding frame and the lower package cover structure below the plurality of sound-speaking fins, wherein the upper package cover structure and/or the lower package cover structure has an acoustic hole.
A method for forming a fin structure loudspeaker, characterized in that it comprises:

processing the wafer into a surrounding frame and a plurality of fin bases within the surrounding frame;

A piezoelectric layer with an uneven thickness is formed on the surfaces of the two vertical side walls of the fin base, and the fin base and the piezoelectric layer form a sound-speaking fin.
The method for forming a fin structure loudspeaker according to claim 17, characterized in that the material of the fin base is silicon.
The loudspeaker with fin structure according to claim 17, characterized in that the crystal phases of the piezoelectric layers on the surfaces of the two vertical side walls of the same fin base are opposite.
The method for forming a fin structure loudspeaker according to claim 17, characterized in that the cross-section of the piezoelectric layer is wedge-shaped.
The method for forming a fin structure loudspeaker according to claim 20, characterized in that:

The piezoelectric layer has a maximum width at a position closest to the top and bottom ends of the speaker fin, and the piezoelectric layer has a minimum width at a position closest to the middle of the speaker fin; or,

The piezoelectric layer has a maximum width at a position closest to one of the top end and the bottom end of the speaker fin, and the piezoelectric layer has a maximum width at a position closest to the top end and the bottom end of the speaker fin. The position of the other of the two has the smallest width.
The method for forming a fin structure loudspeaker according to claim 20, wherein the angle between the outer surface of the piezoelectric layer and the vertical side wall surface of the fin base is defined as a first angle, and the The value range of the first included angle is 0 to 45°.
The method for forming a fin structure speaker according to claim 20, wherein the piezoelectric layer is defined to cover the length of the vertical side wall of the fin base and the entire length of the vertical side wall of the fin base The ratio of is the coverage ratio of the piezoelectric layer, and the range of the ratio of the coverage ratio of the piezoelectric layer is 10% to 100%, or 30% to 60%.
The method for forming a fin structure loudspeaker according to claim 17, further comprising: forming an external electrode on the surface of the piezoelectric layer.
The method for forming a fin structure loudspeaker according to claim 24, wherein the angle between the outer surface of the external electrode and the outer surface of the piezoelectric layer is defined as a second angle, and the second angle is Angle ranges from 0 to 45°.
The method for forming a fin structure loudspeaker according to claim 24, characterized in that the thickness of the piezoelectric layer below the ends of the external electrodes is greater than 100 nanometers.
The method for forming a fin structure loudspeaker according to claim 24, wherein the covering area of the external electrode is smaller than the covering area of the piezoelectric layer.
The method for forming a fin structure loudspeaker according to claim 17, further comprising: forming an internal electrode between the fin base and the piezoelectric layer.
The method for forming a fin structure speaker according to claim 17, wherein the piezoelectric layers on both sides of the sound speaker fin are independently powered.
The method for forming a fin structure loudspeaker according to claim 17, wherein the piezoelectric layer material is: aluminum nitride, PZT, zinc oxide or a doped material of the above materials.
The method for forming a fin structure loudspeaker according to claim 17, wherein the piezoelectric layer is in the form of a thin film with an average thickness of 0.1 microns to 10 microns.
The method for forming a fin structure loudspeaker according to any one of claims 17 to 31, further comprising: encapsulating an upper encapsulation cover structure above the surrounding frame and the plurality of sound-speaking fins; A lower encapsulation lid structure is encapsulated under the surrounding frame and the plurality of sound-speaking fins, wherein the upper encapsulation lid structure and/or the lower encapsulation lid structure has an acoustic hole.