Lamb wave resonator and preparation method thereof

Abstract

The invention relates to a Lamb wave resonator and a preparation method thereof. The preparation method comprises the following steps: providing a piezoelectric film; the interdigital electrode and the bus bar are positioned above the piezoelectric film; the functional heat dissipation film is positioned below the piezoelectric film; the supporting substrate is positioned below the functional heat dissipation film; high aspect ratio grooves which are periodically arranged or non-periodically arranged are formed in the bottom of the functional heat dissipation film; and the piezoelectric film area corresponding to the interdigital electrode is suspended. Through the arrangement of the fin heat dissipation structure, the contact area of the film and air is greatly increased, the heat dissipation capability of the resonator is remarkably enhanced, and the power capacity and the heat stability of the resonator are further enhanced; meanwhile, the structure can suppress resonance of a spurious mode in the resonator by scattering sound waves, plays a role in suppressing the spurious mode, and has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of resonators, and in particular relates to a Lamb wave resonator and a preparation method thereof. Background Art

[0002] Compared with traditional solid-state assembled resonators, resonators based on suspended piezoelectric films can excite modes with relatively high acoustic velocities and large electromechanical coupling coefficients, and can thus be used as a component of high-frequency, wide-bandwidth filters. In recent years, suspended film resonators based on SH0 / S0 / A1 modes have received great attention from the industry. However, since the film is suspended in the air, the heat generated by the vibration of the resonator cannot be dissipated. Compared with solid-state assembled resonators, its power capacity and thermal stability are greatly reduced, which has become a major factor restricting its application. Therefore, how to improve the heat dissipation of suspended resonators and thus enhance their stability is a very important task and a problem that needs to be solved urgently.

[0003] The existing methods are mainly based on heterogeneous integrated materials such as lithium niobate / lithium tantalate film (piezoelectric film)-silicon dioxide intermediate layer-silicon substrate, or lithium niobate / lithium tantalate film-silicon substrate, and the release window is formed by etching lithium niobate / lithium tantalate, or the silicon dioxide and silicon under the device are released by back etching to form a lithium niobate / lithium tantalate suspended film. Due to the extremely low thermal conductivity of air, the heat generated by this single film cannot be dissipated.

[0004] US20200350890A1 proposes a method of etching holes to suppress the stray mode based on the traditional thin film Lamb wave resonator. However, the thin film is still a single material film, its heat cannot be effectively dissipated, and the power capacity is low.

[0005] CN113676149B and CN113922784B are both based on suspended piezoelectric films, and the electrode shape is finely adjusted to suppress the stray mode. However, the film is still a single material film, its heat cannot be effectively dissipated, and the power capacity is low.

[0006] CN116318023B has a groove on the back, but the depth and width of the groove on the back are relatively small, and most of them are flat structures, and they must be coordinated with the position of the electrodes. The purpose is mainly to suppress stray modes, not to increase heat dissipation.

[0007] In traditional solid-state assembly devices, an effective way to improve heat dissipation is to transfer lithium niobate / lithium tantalate film to a high thermal conductivity substrate (such as a silicon carbide substrate), so that the generated heat can be dissipated through the silicon carbide substrate. However, in a suspended film structure, there is no stable path for heat dissipation. Therefore, simply integrating the piezoelectric film with other films does not significantly change its heat dissipation area, and the contact area with the air remains almost unchanged, so the improvement in heat dissipation capacity is limited. Summary of the invention

[0008] The present invention provides a Lamb wave resonator and a preparation method thereof, and aims to solve the problem that a single suspended piezoelectric film and a heterogeneous integrated piezoelectric film have small heat dissipation areas and poor heat dissipation capabilities.

[0009] The present invention provides a Lamb wave resonator, wherein the Lamb wave resonator structure comprises:

[0010] Providing a piezoelectric film;

[0011] interdigitated electrodes and bus bars located above the piezoelectric film;

[0012] A functional heat dissipation film located below the piezoelectric film;

[0013] A supporting substrate located below the functional heat dissipation film;

[0014] The bottom of the functional heat dissipation film is provided with periodically or non-periodically arranged high aspect ratio grooves;

[0015] The piezoelectric film region corresponding to the interdigital electrodes is suspended.

[0016] Preferably, the material of the piezoelectric film is one or more of lithium niobate and lithium tantalate; the crystal cut of the piezoelectric film is a rotated Y cut, and the corresponding Euler angle is (0, -β, 0); or an X cut, and the corresponding Euler angle is (α, -90, -90); or a Z cut, and the corresponding Euler angle is (α, 0, 0); wherein α and β are arbitrary angles.

[0017] Preferably, the interdigitated electrodes are arranged in a periodic arrangement, and bus bars are provided at both ends of the interdigitated electrodes.

[0018] Preferably, the material of the interdigital electrodes and the busbar is one or more of aluminum, copper, gold, titanium, nickel, molybdenum and platinum.

[0019] Preferably, the material of the functional heat dissipation film is one or more of 4H-silicon carbide, 6H-silicon carbide and diamond.

[0020] Preferably, the ratio of the width to the height of the high aspect ratio groove is >2.

[0021] Furthermore, a dielectric film is provided between the functional heat dissipation film and the supporting substrate.

[0022] Preferably, the material of the dielectric film is silicon dioxide.

[0023] The present invention also provides a method for preparing a Lamb wave resonator, comprising the following steps:

[0024] S1, preparing a piezoelectric film-support substrate and a functional heat dissipation film-support substrate;

[0025] S2, bonding the piezoelectric film-support substrate and the functional heat dissipation film-support substrate, wherein the piezoelectric film and the functional heat dissipation film are in contact with each other;

[0026] S3, removing the supporting substrate on one side to form a piezoelectric film-functional heat dissipation film-supporting substrate structure;

[0027] S4, preparing interdigital electrodes and bus bars on the piezoelectric film;

[0028] S5, back etching to form a cavity structure, so that the supporting substrate under the interdigital electrodes is suspended;

[0029] S6, performing back etching on the functional heat dissipation film to form periodically or non-periodically arranged grooves with high aspect ratio.

[0030] The present invention also provides a method for preparing a Lamb wave resonator, comprising the following steps:

[0031] S1, preparing a piezoelectric film-support substrate and a functional heat dissipation film-support substrate;

[0032] S2, etching the functional heat dissipation film to form periodically arranged or non-periodically arranged high aspect ratio grooves;

[0033] S3, bonding the piezoelectric film-support substrate and the functional heat dissipation film-support substrate, wherein the piezoelectric film and the functional heat dissipation film are in contact with each other;

[0034] S4, removing the supporting substrate on one side to form a piezoelectric film-functional heat dissipation film-supporting substrate structure;

[0035] S5. preparing interdigital electrodes and bus bars on the piezoelectric film;

[0036] S6. Back etching is performed to form a cavity structure, so that the supporting substrate under the interdigital electrodes is suspended.

[0037] Beneficial Effects

[0038] The present invention greatly increases the contact area between the film and the air by providing a fin heat dissipation structure, significantly enhancing the heat dissipation capacity of the resonator, thereby enhancing its power capacity and thermal stability; at the same time, the structure can also suppress the resonance of stray modes in the resonator by scattering sound waves, thereby playing a role in suppressing stray modes and having good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagrams of two structures of the Lamb wave resonator of the present invention.

[0040] Figure 2 It is a partial enlarged view of the interdigital electrode and the functional heat dissipation film of the present invention.

[0041] Figure 3 It is a partial enlarged view of the top of the functional heat dissipation film of the present invention.

[0042] Figure 4 To compare the heat dissipation area of ​​the functional heat dissipation film after etching and without etching.

[0043] Figure 5 To compare the spurious patterns of the functional heat dissipation film after etching and without etching.

[0044] Figure 6 This is a flow chart of the first preparation process of the Lamb wave resonator of the present invention.

[0045] Figure 7 This is a flow chart of the second preparation process of the Lamb wave resonator of the present invention.

[0046] Figure 8 Schematic diagram of the structure of the Lamb wave resonator of Example 1.

[0047] Fig. 9 This is a partial enlarged view of the Lamb wave resonator of Example 1. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0049] like Figure 1 As shown, the present invention provides a Lamb wave resonator, the structure comprising:

[0050] a piezoelectric film;

[0051] interdigitated electrodes and bus bars located above the piezoelectric film;

[0052] A functional heat dissipation film located below the piezoelectric film;

[0053] A supporting substrate located below the functional heat dissipation film;

[0054] The bottom of the functional heat dissipation film is provided with periodically or non-periodically arranged high aspect ratio grooves (also known as fin-type etched hole structures);

[0055] The piezoelectric film region corresponding to the interdigital electrodes is suspended.

[0056] Optionally, there is a dielectric film between the functional heat dissipation film and the supporting substrate.

[0057] like Figure 2 , Figure 3 As shown, the interdigital electrodes are arranged as a periodic interdigital electrode structure, and bus bars are provided at both ends of the electrodes. λ is defined as twice the period of the interdigital electrodes, and the value range of λ is between 2um and 30um, and the distance Wa between the bus bars is between 40μm and 100μm. Optionally, there are also etched holes between the interdigital electrodes and the bus bars.

[0058] The thickness h1 of the electrode is between 50nm and 800nm, and further, the thickness h1 of the electrode is between 50nm and 200nm. The ratio of the width w1 of the electrode to λ is between 0.05 and 0.25, the thickness h2 of the piezoelectric film is between 200nm and 800nm, and the thickness h3 of the functional heat dissipation film is between 200nm and 800nm.

[0059] The ratio of the width w2 of the high aspect ratio groove to the height h4 satisfies (h4 / w2)>2, and the distance w3 between adjacent grooves satisfies w3 / λ<0.1.

[0060] The material of the interdigital electrodes and the busbars may include a metal material selected from aluminum, copper, gold, titanium, nickel, molybdenum, and platinum, or an alloy material or a multilayer electrode composed of two of the above materials.

[0061] The above-mentioned piezoelectric film material can be a single-layer or multi-layer structure. The single-layer structure can choose one of lithium niobate or lithium tantalate, and the multi-layer structure can be a combination of these two materials; the material of the piezoelectric film is one or more of lithium niobate and lithium tantalate; the crystal cut of the piezoelectric film is a rotated Y-cut, and the corresponding Euler angle is (0, -β, 0); or an X-cut, and the corresponding Euler angle is (α, -90, -90); or a Z-cut, and the corresponding Euler angle is (α, 0, 0); wherein α and β are arbitrary angles.

[0062] The functional heat dissipation film material is one or more of 4H-silicon carbide, 6H-silicon carbide and diamond.

[0063] The material of the supporting substrate is silicon, and the resistance is greater than 10000Ω·cm.

[0064] The material of the dielectric film is silicon dioxide.

[0065] This structure increases the contact area between the bottom of the film and the air by etching, thereby increasing the heat dissipation area and improving the heat dissipation effect of the resonator. Taking the film area of ​​100um×100um as an example, the heat dissipation area without etching the functional heat dissipation film layer is fixed at 10000um. 2However, after the groove structure is etched, the fin-type heat dissipation structure increases linearly with the etching depth. When the etching depth is 150nm, its heat dissipation area can reach 4 times that of the unetched state.

[0066] The structure scatters the stray modes reflected up and down in the resonator through the irregular structure at the bottom, which can suppress the stray modes. After applying the fin-type etched hole structure, the stray modes around the anti-resonance are significantly suppressed.

[0067] like Figure 6 As shown, the present invention also provides a method for preparing the structure:

[0068] S1. Prepare piezoelectric film-support substrate and functional heat dissipation film-support substrate structure: The composite structure can be formed by pre-implanting ions on the piezoelectric layer or the functional heat dissipation layer, bonding with the support substrate, and finally peeling off to form a piezoelectric film-support substrate and a functional heat dissipation film-support substrate structure.

[0069] S2. Bonding the two, wherein the piezoelectric film and the functional heat dissipation film are in contact with each other.

[0070] S3. Remove the supporting substrate on one side to form a piezoelectric film-functional heat dissipation film-supporting substrate structure.

[0071] S4. Prepare interdigital electrodes and busbars on the piezoelectric film: Deposit a layer of photoresist on LN-SiC by spin coating. Use electron beam lithography (EBL) to pattern the electrodes. Deposit a layer of metal. If a multi-layer metal structure is required, multiple depositions are required. The photoresist is removed by lift-off process, and the electrode structure is completed.

[0072] S5. Back etching to form a cavity structure, so that the supporting substrate under the interdigital electrodes is suspended.

[0073] S6. Perform back etching on the functional heat dissipation film to form periodically or non-periodically arranged grooves with high aspect ratio.

[0074] like Figure 7 As shown, the present invention also provides a method for preparing the structure:

[0075] S1. Prepare piezoelectric film-support substrate and functional heat dissipation film-support substrate structure: The composite structure can be formed by pre-implanting ions on the piezoelectric layer or the functional heat dissipation layer, bonding with the support substrate, and finally peeling off to form a piezoelectric film-support substrate and a functional heat dissipation film-support substrate structure.

[0076] S2. Etching the functional heat dissipation layer to form periodically or non-periodically arranged grooves with high aspect ratio.

[0077] S3. Bonding the two together, wherein the piezoelectric film and the functional heat dissipation film are in contact with each other.

[0078] S4. Remove the supporting substrate on one side to form a piezoelectric film-functional heat dissipation film-supporting substrate structure.

[0079] S5. Prepare interdigital electrodes and busbars on the piezoelectric film: Deposit a layer of photoresist on the LN-SiC by spin coating. Use electron beam lithography (EBL) to pattern the electrodes. Deposit a layer of metal. If a multi-layer metal structure is required, multiple depositions are required. The lift-off process removes the photoresist and the electrode structure is completed.

[0080] S6. Back etching to form a cavity structure, so that the supporting substrate under the interdigital electrodes is suspended.

[0081] Example

[0082] The metal material of the interdigital electrode is set to be aluminum, the piezoelectric film material is lithium niobate, the heat dissipation film material is 300nm SiC, and there are 50nm wide and 150nm deep etched holes on the back of the SiC, and the distance between the holes is 200nm (such as Figure 8 and Fig. 9 As shown). Compared with the normal structure without holes, the contact area between the heat dissipation film and the air is increased by 2 times, and the stray mode on the right side of the anti-resonance peak of the admittance curve is suppressed, as shown in Figure 4 and Figure 5 As shown in Figure 2, the resonator improved by the fin-etched hole structure has higher power capacity and better thermal stability.

Claims

1. A Lamb wave resonator, characterized in that: The Lamb wave resonator structure comprises: Providing a piezoelectric film; interdigitated electrodes and bus bars located above the piezoelectric film; A functional heat dissipation film located below the piezoelectric film; A supporting substrate located below the functional heat dissipation film; The bottom of the functional heat dissipation film is provided with periodically or non-periodically arranged high aspect ratio grooves; The piezoelectric film region corresponding to the interdigital electrodes is suspended.

2. The Lamb wave resonator according to claim 1, characterized in that: The material of the piezoelectric film is one or more of lithium niobate and lithium tantalate; the crystal cut of the piezoelectric film is a rotated Y cut, and the corresponding Euler angle is (0, -β, 0); or For X-cut, the corresponding Euler angle is (α, -90, -90); or for Z-cut, the corresponding Euler angle is (α, 0, 0); where α and β are arbitrary angles.

3. The Lamb wave resonator according to claim 1, characterized in that: The interdigital electrodes are arranged in a periodic arrangement, and bus bars are provided at both ends of the interdigital electrodes.

4. The Lamb wave resonator according to claim 1, characterized in that: The materials of the interdigital electrodes and the busbars are one or more of aluminum, copper, gold, titanium, nickel, molybdenum and platinum.

5. The Lamb wave resonator according to claim 1, characterized in that: The material of the functional heat dissipation film is one or more of 4H-silicon carbide, 6H-silicon carbide and diamond.

6. The Lamb wave resonator according to claim 1, characterized in that: The ratio of the width to the height of the high aspect ratio groove is greater than 2.

7. The Lamb wave resonator according to claim 1, characterized in that: A dielectric film is also provided between the functional heat dissipation film and the supporting substrate.

8. The Lamb wave resonator according to claim 7, characterized in that: The material of the dielectric film is silicon dioxide.

9. A method for preparing a Lamb wave resonator, comprising the following steps: S1, preparing a piezoelectric film-support substrate and a functional heat dissipation film-support substrate; S2, bonding the piezoelectric film-support substrate and the functional heat dissipation film-support substrate, wherein the piezoelectric film and the functional heat dissipation film are in contact with each other; S3, removing the supporting substrate on one side to form a piezoelectric film-functional heat dissipation film-supporting substrate structure; S4, preparing interdigital electrodes and bus bars on the piezoelectric film; S5, back etching to form a cavity structure, so that the supporting substrate under the interdigital electrodes is suspended; S6, performing back etching on the functional heat dissipation film to form periodically or non-periodically arranged grooves with high aspect ratio.

10. A method for preparing a Lamb wave resonator, comprising the following steps: S1, preparing a piezoelectric film-support substrate and a functional heat dissipation film-support substrate; S2, etching the functional heat dissipation film to form periodically arranged or non-periodically arranged high aspect ratio grooves; S3, bonding the piezoelectric film-support substrate and the functional heat dissipation film-support substrate, wherein the piezoelectric film and the functional heat dissipation film are in contact with each other; S4, removing the supporting substrate on one side to form a piezoelectric film-functional heat dissipation film-supporting substrate structure; S5. preparing interdigital electrodes and bus bars on the piezoelectric film; S6. Back etching is performed to form a cavity structure, so that the supporting substrate under the interdigital electrodes is suspended.

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