Scandium-doped aluminum nitride film and preparation method of flexible surface acoustic wave resonator

Abstract

The invention provides a scandium-doped aluminum nitride film and a preparation method of a flexible surface acoustic wave resonator, and relates to the technical field of semiconductor device manufacturing. The preparation method of the scandium-doped aluminum nitride film comprises the following steps: sequentially epitaxially growing a two-dimensional material layer, a buffer layer and a scandium-doped aluminum nitride film layer which are stacked on a first substrate, and preparing a crystal layer; removing the first substrate, the two-dimensional material layer and the buffer layer to obtain a scandium-doped aluminum nitride film; wherein the material of the two-dimensional material layer comprises one of graphene, hexagonal boron nitride and two-dimensional transition metal sulfide; the buffer layer is made of aluminum nitride.

Description

Technical Field

[0001] The present disclosure relates to the technical field of semiconductor device manufacturing, and more particularly, to a method for preparing a scandium-doped aluminum nitride film and a flexible surface acoustic wave resonator. Background Art

[0002] Flexible surface acoustic wave (SAW) devices have been widely used in wearable electronics, lab-on-a-chip (LACs), and various flexible sensors (e.g., humidity, temperature, UV, and biochemical). With the rapid development of 5G communication technology and the widespread adoption of the Internet of Things (IoT), the demand for high-performance, high-frequency flexible SAW devices is becoming increasingly urgent. Piezoelectric film is the core material of SAW devices. Its physical properties significantly influence the resonant frequency, electromechanical coupling coefficient, and frequency-temperature coefficient of SAW devices, and are a major challenge facing high-performance, high-frequency flexible SAW devices.

[0003] Traditional piezoelectric materials (such as quartz, ) suffer from poor CMOS process compatibility and complex manufacturing. While AlN, while compatible with complementary metal-oxide-semiconductor (CMOS), is limited by its low electromechanical coupling coefficient (<1%), it struggles to meet broadband filtering requirements. Although scandium-doped aluminum nitride (AlScN) is considered an ideal alternative due to its excellent piezoelectric properties, the quality of AlScN films grown epitaxially on high-frequency substrates (such as diamond) is poor, and the exfoliation process is complex and costly. Summary of the Invention

[0004] In view of this, the present disclosure provides a method for preparing a scandium-doped aluminum nitride film and a flexible surface acoustic wave resonator.

[0005] On the one hand, the present disclosure provides a method for preparing a scandium-doped aluminum nitride thin film, comprising: epitaxially growing a stacked two-dimensional material layer, a buffer layer and a scandium-doped aluminum nitride thin film layer on a first substrate in sequence to prepare a crystal layer; removing the first substrate, the two-dimensional material layer and the buffer layer to obtain the scandium-doped aluminum nitride thin film; wherein the material of the two-dimensional material layer comprises one of graphene, hexagonal boron nitride and two-dimensional transition metal sulfide; and the material of the buffer layer comprises aluminum nitride.

[0006] According to an embodiment of the present disclosure, epitaxially growing a two-dimensional material layer on a first substrate includes: epitaxially growing a two-dimensional material on the first substrate; and performing plasma treatment on the two-dimensional material to obtain the two-dimensional material layer.

[0007] According to an embodiment of the present disclosure, epitaxially growing a two-dimensional material on a first substrate includes: epitaxially growing graphene with a thickness of 1 to 2 layers on the first substrate, and the coverage of each layer of graphene is greater than 98%; or, epitaxially growing hexagonal boron nitride with a thickness of less than 1 nm on the first substrate at a temperature of 1000°C to 1500°C.

[0008] According to an embodiment of the present disclosure, epitaxial growth of a buffer layer on a two-dimensional material layer includes: growing a first aluminum nitride layer on the two-dimensional material layer at a temperature of 600°C to 900°C; and growing a second aluminum nitride layer on the first aluminum nitride layer at a temperature of 1200°C to 1400°C; wherein the thickness of the first aluminum nitride layer is 20nm to 50nm, and the thickness of the second aluminum nitride layer is 1μm to 2μm.

[0009] According to the embodiment of the present disclosure, the thickness of the scandium-doped aluminum nitride thin film layer is 1 μm to 2 μm; the atomic percentage of the scandium component in the scandium-doped aluminum nitride thin film layer is .

[0010] According to an embodiment of the present disclosure, the first substrate includes one of a sapphire substrate, a silicon carbide substrate, and a silicon substrate.

[0011] According to an embodiment of the present disclosure, removing the first substrate, the two-dimensional material layer and the buffer layer in the crystal layer includes: placing the crystal layer in an acidic solution to peel off the first substrate and the two-dimensional material layer to obtain a scandium-doped aluminum nitride film containing a buffer layer; etching the buffer layer in the scandium-doped aluminum nitride film containing a buffer layer to obtain a scandium-doped aluminum nitride film.

[0012] A second aspect of the present disclosure provides a method for preparing a flexible surface acoustic wave resonator, comprising: epitaxially growing a stacked two-dimensional material layer, a buffer layer, a scandium-doped aluminum nitride thin film layer and a diamond layer on a first substrate in sequence to prepare a first wafer structure; epitaxially growing an oxide layer on a second substrate; bonding a flexible substrate to a surface of the oxide layer away from the second substrate to prepare a second wafer structure; bonding a surface of the diamond layer away from the scandium-doped aluminum nitride thin film layer to a surface of the flexible substrate away from the oxide layer to prepare a third wafer structure; removing the first substrate, two-dimensional material layer, buffer layer, oxide layer and second substrate from the third wafer structure; preparing interdigitated electrodes on the scandium-doped aluminum nitride thin film layer in the third wafer structure to obtain a flexible surface acoustic wave resonator; wherein the material of the two-dimensional material layer comprises one of graphene, hexagonal boron nitride and two-dimensional transition metal sulfide; and the material of the buffer layer comprises aluminum nitride.

[0013] According to an embodiment of the present disclosure, interdigital electrodes are prepared on the scandium-doped aluminum nitride thin film layer in the third chip structure, including: patterning the scandium-doped aluminum nitride thin film by photolithography; sequentially evaporating a first metal material layer and a second metal material layer on the patterned scandium-doped aluminum nitride thin film, and etching and peeling to prepare interdigital electrodes.

[0014] According to an embodiment of the present disclosure, the thickness of the first metal material layer is 10 nm, and the thickness of the second metal material layer is 80 nm to 300 nm.

[0015] The method for preparing a scandium-doped aluminum nitride thin film provided in the embodiments of the present disclosure has at least the following beneficial effects:

[0016] This method, which sequentially epitaxially grows a two-dimensional material layer, a buffer layer, and a scandium-doped aluminum nitride thin film on a substrate, effectively reduces the lattice mismatch stress associated with traditional direct growth and significantly improves the crystalline quality of the AlScN film. Furthermore, the two-dimensional material can be used to assist in substrate debonding, eliminating the need for laser debonding, resulting in a simple and low-cost process.

[0017] By using a rigid single-crystal substrate epitaxial growth process, a non-polar AlScN thin film with a specific crystal orientation can be obtained, thus enabling the fabrication of flexible SAW resonators with a non-polar AlScN / diamond structure. This method leverages the synergistic advantages of the enhanced electromechanical coupling efficiency of the non-polar AlScN film and the ultra-high acoustic velocity characteristics of the diamond substrate, providing a breakthrough solution for the development of high-performance, high-frequency flexible SAW resonators. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0019] Figure 1 A flow chart schematically illustrates a method for preparing a scandium-doped aluminum nitride thin film according to an embodiment of the present disclosure;

[0020] Figure 2 Schematically shows a schematic diagram of a first wafer structure according to an embodiment of the present disclosure;

[0021] Figure 3 Schematically shows a schematic diagram of a second wafer structure according to an embodiment of the present disclosure;

[0022] Figure 4 Schematically shows a schematic diagram of a third wafer structure according to an embodiment of the present disclosure;

[0023] Figure 5 Schematic diagram of an interdigitated electrode according to an embodiment of the present disclosure is schematically shown;

[0024] Figure 6 The figure schematically shows the structure of a flexible surface acoustic wave resonator according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may be implemented without these specific details. In addition, in the following description, descriptions of well-known systems and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0026] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0027] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0028] When expressions such as "at least one of A, B, and C, etc." are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0029] Currently commercial SAW devices are made of bulk piezoelectric materials such as quartz and LiNbO3, which have problems related to CMOS compatibility and manufacturing complexity. AlN has the characteristics of high longitudinal wave sound velocity, low intrinsic loss and CMOS process compatibility, making it the preferred piezoelectric material for SAW devices. However, the electromechanical coupling coefficient of AlN is relatively low (<1%), which limits the bandwidth of the filter. In the past decade, AlScN has been considered the most promising material for the next generation of high-frequency SAW devices due to its excellent piezoelectric properties. Diamond has extremely high sound velocity (18200 m / s) and thermal conductivity (over 1000 ), is an ideal substrate material for high-frequency SAW devices. SAW waves are effectively waveguided along the film, creating favorable conditions for increasing the electromechanical coupling coefficient and exciting higher-order SAW modes. Therefore, AlScN film, due to its excellent piezoelectric properties and low loss characteristics, combined with diamond, can significantly improve the performance of SAW devices and is considered a promising platform.

[0030] The fabrication of flexible SAW resonators based on AlScN / diamond structures involves, on the one hand, the traditional method of growing AlScN thin films on diamond. However, due to the lack of high-quality diamond substrates, the resulting AlScN films often have poor crystal quality. On the other hand, the traditional method of obtaining flexible AlScN is to grow it on a rigid substrate and then remove the rigid substrate by laser lift-off or etching, which results in a complex and costly process. Furthermore, SAW resonators based on non-polar AlScN thin films have attracted attention due to their enhanced electromechanical coupling coefficient and high-frequency characteristics. However, SAW resonators based on flexible non-polar AlScN / diamond structures have not been reported.

[0031] Figure 1 The flowchart of the method for preparing a scandium-doped aluminum nitride thin film according to an embodiment of the present disclosure is schematically shown.

[0032] like Figure 1 As shown, this embodiment discloses a method for preparing a scandium-doped aluminum nitride thin film, including steps S100 to S110.

[0033] In step S100 , a stacked two-dimensional material layer, a buffer layer, and a scandium-doped aluminum nitride thin film layer are epitaxially grown in sequence on a first substrate to prepare a crystal layer.

[0034] In step S110 : the first substrate, the two-dimensional material layer and the buffer layer are removed to obtain a scandium-doped aluminum nitride thin film.

[0035] The material of the two-dimensional material layer includes one of graphene, hexagonal boron nitride and two-dimensional transition metal sulfide; the material of the buffer layer includes aluminum nitride.

[0036] In the embodiments disclosed herein, a two-dimensional material layer is epitaxially grown on a first substrate. The atomically flat surface of the two-dimensional material, the adaptive hexagonal lattice structure of graphene and hexagonal boron nitride, and the weak interlayer van der Waals forces can effectively reduce the lattice mismatch between the substrate layer and the scandium-doped aluminum nitride thin film layer, enabling quasi-van der Waals epitaxy and flexible exfoliation. Furthermore, by providing a high-quality aluminum nitride buffer layer between the two-dimensional material layer and the scandium-doped aluminum nitride thin film layer, defect reduction and a gradual stress transition are achieved, effectively improving the crystal quality of the scandium-doped aluminum nitride layer and reducing mismatch stress. This method utilizes the adaptive lattice structure and interlayer van der Waals forces of the two-dimensional material as a flexible exfoliation layer; the aluminum nitride buffer layer provides a low-defect-density seed layer, reducing the defect density of the scandium-doped aluminum nitride. This results in high-quality scandium-doped aluminum nitride thin films, with XRD symmetric diffraction half-maximum widths less than 1 degree, far less than the existing minimum of 1.5 degrees, and high electromechanical coupling efficiency.

[0037] Based on the above embodiment, epitaxially growing a two-dimensional material layer on the first substrate includes: epitaxially growing a two-dimensional material on the first substrate, and performing plasma treatment on the two-dimensional material to obtain the two-dimensional material layer.

[0038] Furthermore, the epitaxially grown two-dimensional material was plasma treated for 3 minutes in a nitrogen atmosphere at a power of 100 W to clean the surface of the two-dimensional material and improve the surface activity.

[0039] According to an embodiment of the present disclosure, epitaxially growing a two-dimensional material on a first substrate includes: epitaxially growing graphene with a thickness of 1 to 2 layers on the first substrate using chemical vapor deposition, and the coverage of each layer of graphene is greater than 98%.

[0040] Alternatively, hexagonal boron nitride (HBN) with a thickness of less than 1 nm is epitaxially grown on a first substrate using metal organic chemical vapor deposition (MOCVD) at a temperature of 1000°C to 1500°C. A periodic triethylboron (TEB) / NH3 growth method is used during the growth process, and the thickness of the HBN is controlled by the number of cycles.

[0041] According to an embodiment of the present disclosure, epitaxially growing a buffer layer on a two-dimensional material layer includes: growing a first aluminum nitride layer with a thickness of 20 nm to 50 nm on the two-dimensional material layer at a temperature of 600°C to 900°C as a nucleation layer. Growing a second aluminum nitride layer with a thickness of 1 μm to 2 μm on the first aluminum nitride layer at a temperature of 1200°C to 1400°C, thereby obtaining an aluminum nitride layer with a low defect density and an XRD symmetric swing width at half maximum of less than 100 arc seconds. The aluminum nitride is epitaxially grown using metal-organic chemical vapor deposition (MOCVD) with trimethylaluminum (TMA) and NH3 as source gases and H2 as carrier gas.

[0042] In the embodiments disclosed herein, the first aluminum nitride layer serves as low-temperature aluminum nitride, and the second aluminum nitride layer serves as high-temperature aluminum nitride. The low-temperature aluminum nitride layer serves as a nucleation layer, while the high-temperature aluminum nitride layer serves as a crystal quality enhancement layer. This allows for a high-quality aluminum nitride layer to be obtained and used as a buffer layer for scandium-doped aluminum nitride. Its low defect density can reduce the dislocation density of the scandium-doped aluminum nitride, effectively improving the quality of the resulting scandium-doped aluminum nitride film.

[0043] According to an embodiment of the present disclosure, a scandium-doped aluminum nitride thin film layer with a thickness of 1 μm to 2 μm is grown by magnetron sputtering, MOCVD or molecular beam epitaxy (MBE), and the atomic percentage of the scandium component in the scandium-doped aluminum nitride thin film layer is .

[0044] According to an embodiment of the present disclosure, the first substrate includes one of a sapphire substrate, a silicon carbide substrate, and a silicon substrate.

[0045] In the embodiment of the present disclosure, the first substrate is a single crystal substrate. The atomically flat surface and strictly periodic lattice arrangement of the single crystal substrate are utilized to provide precise crystallographic guidance for the epitaxial growth of subsequent two-dimensional material layers and buffer layers, thereby ensuring the single crystallinity of the thin film.

[0046] According to an embodiment of the present disclosure, removing the first substrate, the two-dimensional material layer, and the buffer layer from the crystal layer includes placing the crystal layer in a dilute acidic solution to peel off the first substrate and the two-dimensional material layer, thereby obtaining a scandium-doped aluminum nitride film including a buffer layer. Etching the buffer layer in the scandium-doped aluminum nitride film including the buffer layer using inductively coupled plasma etching to obtain the scandium-doped aluminum nitride film.

[0047] In the embodiments of the present disclosure, a method is provided that can achieve precise control of selective stripping, which can completely strip the substrate and the two-dimensional material layer, and the entire stripping process is carried out at room temperature. This avoids the local thermal stress problem that may occur in the traditional laser stripping process and effectively protects the integrity of the interface. The buffer layer is then etched to ensure that the thickness of the prepared scandium-doped aluminum nitride film is uniform and consistent. The film treated by this method not only has superior performance, but also has a simple process flow and low cost.

[0048] Figure 2 A schematic diagram of a first wafer structure according to an embodiment of the present disclosure is schematically shown.

[0049] Figure 3 A schematic diagram of a second wafer structure according to an embodiment of the present disclosure is schematically shown.

[0050] Figure 4 A schematic diagram of a third wafer structure according to an embodiment of the present disclosure is schematically shown.

[0051] Figure 5 A schematic diagram of an interdigitated electrode according to an embodiment of the present disclosure is schematically shown.

[0052] Figure 6 The figure schematically shows the structure of a flexible surface acoustic wave resonator according to an embodiment of the present disclosure.

[0053] like Figure 2-Figure 6 As shown, this embodiment discloses a method for preparing a flexible surface acoustic wave resonator, comprising:

[0054] A first wafer structure is prepared by sequentially epitaxially growing a stacked two-dimensional material layer 20, a buffer layer 30, a scandium-doped aluminum nitride thin film layer 40, and a diamond layer 50 on a first substrate 10. Figure 2 shown.

[0055] An oxide layer 70 is epitaxially grown on the second substrate 60 .

[0056] Furthermore, the material of the second substrate 60 includes a sapphire substrate, a silicon carbide substrate, a silicon substrate, and other hard wafers, such as a glass wafer and a metal film.

[0057] A flexible substrate 80 is bonded to the side of the oxide layer 70 away from the second substrate 60 to prepare a second wafer structure, such as Figure 3 shown.

[0058] Furthermore, the material of the flexible substrate 80 includes polyimide (PI), polyethylene terephthalate (PET), metal film, and ultra-thin glass.

[0059] The surface of the diamond layer 50 away from the scandium-doped aluminum nitride film layer 40 is bonded to the surface of the flexible substrate 80 away from the oxide layer 70 by an adhesive to prepare a third wafer structure, such as Figure 4 shown.

[0060] The first substrate 10 , the two-dimensional material layer 20 , the buffer layer 30 , the oxide layer 70 and the second substrate 60 in the third wafer structure are removed.

[0061] Interdigital electrodes are prepared on the scandium-doped aluminum nitride thin film layer 40 in the third wafer structure to obtain a flexible surface acoustic wave resonator, such as Figure 6 shown.

[0062] Furthermore, the interdigitated electrode patterns include single-port, dual-port, and delay line forms. The electrode materials include metals Al / Ti, Pt / Ti, and Au / Ti.

[0063] The material of the two-dimensional material layer 20 includes one of graphene, hexagonal boron nitride and two-dimensional transition metal sulfide; the material of the buffer layer 30 includes aluminum nitride.

[0064] In the embodiments disclosed herein, by growing a non-polar AlScN film on a suitable rigid single crystal substrate, the internal electric field problem caused by the polarization effect can be avoided. This not only helps to improve the quality of the film, but also enhances the stability and reliability of the device. At the same time, the acoustic velocity characteristics of diamond are utilized to enable the prepared flexible SAW resonator to have high-frequency operating capabilities and excellent performance. In addition, this method has a simple process and is easy to operate, while reducing production costs, which is conducive to large-scale production and application promotion.

[0065] Based on the above embodiment, interdigital electrodes are formed on the scandium-doped aluminum nitride thin film layer in the third wafer structure, including: patterning the scandium-doped aluminum nitride thin film by photolithography; sequentially evaporating a first metal material layer having a thickness of 10 nm and a second metal material layer having a thickness of 80 nm to 300 nm on the patterned scandium-doped aluminum nitride thin film; and then etching and stripping the resulting interdigital electrodes.

[0066] In some possible embodiments, a method for preparing a flexible surface acoustic wave resonator is provided, comprising:

[0067] Step S1-A: Take a c-plane sapphire wafer 10 and grow a two-dimensional h-BN layer 20 using MOCVD. The h-BN thickness is controlled to be within 1 nm by adjusting the number of TEB / NH3 pulse cycles.

[0068] Sub-step S1-B: plasma-treating the h-BN for 3 to 5 minutes under a N2 atmosphere and a power of 100 W;

[0069] Sub-step S1-C: growing an AlN buffer layer 30 on the h-BN by MOCVD, wherein the AlN buffer layer 30 comprises a low-temperature AlN layer with a thickness of 20 nm to 50 nm and a high-temperature AlN layer with a thickness of 200 nm to 1000 nm.

[0070] Sub-step S1-D: growing an AlScN layer 40 with a thickness of 1000 nm on the AlN buffer layer by magnetron sputtering, wherein the Sc content is adjusted by adjusting the Al / Sc ratio.

[0071] Sub-step S1-E: growing a diamond film layer 50 with a thickness of 10 μm to 100 μm on the AlScN layer 40 by chemical vapor deposition (CVD).

[0072] Furthermore, an r-plane sapphire wafer can be selected in a sub-step to obtain a non-polar AlScN film, and a non-polar / diamond flexible SAW resonator can be prepared. The other steps are the same.

[0073] Step S2, preparing a second wafer structure. This step mainly involves preparing a rigid substrate with a flexible base layer so as to be suitable for preparing interdigital electrodes using a photolithography process, and includes the following sub-steps.

[0074] Sub-step S2-A: Take another sapphire substrate 60 and sputter a 200 nm silicon dioxide layer 70 using PECVD. This oxide layer can be corroded and peeled off the sapphire substrate 60 after the interdigital electrode process is completed.

[0075] Sub-step S2 -B: bonding the other surface of the silicon dioxide layer to the flexible substrate PI layer 80 to form a stacked sapphire substrate 60 , silicon dioxide layer 70 and flexible substrate 80 .

[0076] Step S3: Bond the AlScN-coated diamond film 50 prepared in step S1-E to the flexible substrate prepared in step S2-B. With the aid of a weakly acidic solution, the sapphire layer 10 and the two-dimensional h-BN layer 20 are peeled off. Next, ICP is used to etch the AlN buffer layer 30, exposing the AlScN layer 40 for the interdigital electrodes.

[0077] Step S4: preparing interdigital electrodes on the AlScN layer 40. This includes the following sub-steps:

[0078] Step S4-A: Apply photoresist on the AlScN layer 40, expose and develop, and optimize the process to ensure that the lines of the pattern are complete and the width is consistent.

[0079] Step S4-B: Al / Ti metals are sequentially evaporated on the photoresist-patterned AlScN layer 40 with thicknesses of 10 nm / 90 nm respectively.

[0080] Step S4 -C: Clean the photoresist with a stripper to obtain interdigital electrodes on the AlScN layer 40 .

[0081] Step S5: peeling off the sapphire substrate 60. The sapphire substrate 60 is peeled off with the aid of HF etching of the silicon dioxide layer 70 to obtain an AlScN / diamond flexible SAW resonator.

[0082] Those skilled in the art will appreciate that various combinations and / or combinations of features described in the various embodiments and / or claims of this disclosure may be made, even if such combinations or combinations are not explicitly described in this disclosure. In particular, various combinations and / or combinations of features described in the various embodiments and / or claims of this disclosure may be made, without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0083] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be used in combination to advantage. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A method for preparing a scandium-doped aluminum nitride thin film, characterized in that: include: epitaxially growing a stacked two-dimensional material layer, a buffer layer, and a scandium-doped aluminum nitride thin film layer on a first substrate to prepare a crystal layer; removing the first substrate, the two-dimensional material layer, and the buffer layer to obtain a scandium-doped aluminum nitride thin film; The material of the two-dimensional material layer includes one of graphene, hexagonal boron nitride and two-dimensional transition metal sulfide; the material of the buffer layer includes aluminum nitride.

2. The method according to claim 1, characterized in that Epitaxially growing a two-dimensional material layer on the first substrate comprises: epitaxially growing a two-dimensional material on a first substrate; The two-dimensional material is subjected to plasma treatment to obtain a two-dimensional material layer.

3. The method according to claim 2, characterized in that The epitaxial growth of the two-dimensional material on the first substrate comprises: Epitaxially growing graphene with a thickness of 1 to 2 layers on the first substrate, wherein the coverage of each graphene layer is greater than 98%; Alternatively, hexagonal boron nitride with a thickness of less than 1 nm is epitaxially grown on the first substrate at a temperature of 1000° C. to 1500° C.

4. The method according to claim 1, wherein Epitaxial growth of a buffer layer on a two-dimensional material layer includes: growing a first aluminum nitride layer on the two-dimensional material layer at a temperature of 600° C. to 900° C.; A second aluminum nitride layer is grown on the first aluminum nitride layer at a temperature of 1200° C. to 1400° C., wherein the thickness of the first aluminum nitride layer is 20 nm to 50 nm, and the thickness of the second aluminum nitride layer is 1 μm to 2 μm.

5. The method according to claim 1, wherein The thickness of the scandium-doped aluminum nitride thin film layer is 1 μm to 2 μm; The atomic percentage of scandium component in the scandium-doped aluminum nitride thin film layer is .

6. The method according to claim 1, characterized in that The first substrate includes one of a sapphire substrate, a silicon carbide substrate, and a silicon substrate.

7. The method according to claim 1, characterized in that The removing the first substrate, the two-dimensional material layer, and the buffer layer from the crystal layer comprises: placing the crystal layer in an acidic solution to peel off the first substrate and the two-dimensional material layer, thereby obtaining a scandium-doped aluminum nitride thin film including the buffer layer; The buffer layer in the scandium-doped aluminum nitride thin film including the buffer layer is etched to obtain the scandium-doped aluminum nitride thin film.

8. A method for preparing a flexible surface acoustic wave resonator, characterized in that: include: Epitaxially growing a stacked two-dimensional material layer, a buffer layer, a scandium-doped aluminum nitride thin film layer, and a diamond layer on a first substrate in sequence to prepare a first wafer structure; epitaxially growing an oxide layer on the second substrate; bonding a flexible substrate onto a surface of the oxide layer away from the second substrate to prepare a second wafer structure; bonding a surface of the diamond layer away from the scandium-doped aluminum nitride thin film layer to a surface of the flexible substrate away from the oxide layer to prepare a third wafer structure; removing the first substrate, the two-dimensional material layer, the buffer layer, the oxide layer, and the second substrate from the third wafer structure; Interdigital electrodes are prepared on the scandium-doped aluminum nitride thin film layer in the third wafer structure to obtain a flexible surface acoustic wave resonator; wherein the material of the two-dimensional material layer includes one of graphene, hexagonal boron nitride and two-dimensional transition metal sulfide; and the material of the buffer layer includes aluminum nitride.

9. The method according to claim 7, characterized in that The step of preparing interdigital electrodes on the scandium-doped aluminum nitride thin film layer in the third wafer structure comprises: performing patterning on the scandium-doped aluminum nitride film by photolithography; A first metal material layer and a second metal material layer are sequentially evaporated on the patterned scandium-doped aluminum nitride film, and then subjected to etching and peeling to prepare interdigital electrodes.

10. The method according to claim 9, characterized in that The thickness of the first metal material layer is 10 nm, and the thickness of the second metal material layer is 80 nm to 300 nm.

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