An easily-peeling high-crystalline-quality aluminum scandium nitride film and a method for preparing the same

Abstract

The application provides an easily-peeling high-crystalline-quality aluminum-scandium-nitrogen film and a preparation method thereof, wherein the AlScN film is grown on a two-dimensional BN layer transferred on sapphire by using a sputtering method, a MOCVD method or an MBE method, the peelability is improved, and the material quality is improved through a high-temperature annealing process, so that the easily-peeling high-crystalline-quality aluminum-scandium-nitrogen film can be used in a filter device.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductors, and particularly relates to an aluminum scandium nitride film easy to peel off and high in crystalline quality and a preparation method thereof. BACKGROUND

[0002] In recent years, with the vigorous development of the 5G industry and the development of electronic components in the direction of miniaturization and low power consumption, the material preparation of filters based on thin film bulk acoustic resonators has attracted more and more attention.

[0003] The scandium (Sc) doped aluminum nitride film has higher piezoelectric coefficients and excellent physical and chemical properties and piezoelectricity, and has the characteristics of high hardness, high thermal conductivity, high resistivity, low thermal diffusivity and strong piezoelectricity. These characteristics make the aluminum scandium nitride film widely used in FBAR filter devices.

[0004] However, the current method for growing an aluminum nitride film is to directly grow an aluminum nitride film on a silicon substrate, and the grown film is not easy to peel off from the substrate, thereby affecting the preparation of devices. Therefore, it is an important goal of aluminum nitride film growth to improve the peelability of the aluminum nitride film while ensuring the crystalline quality. SUMMARY

[0005] In order to solve the above problems existing in the prior art, the application provides an aluminum scandium nitride film easy to peel off and high in crystalline quality and a preparation method thereof. The technical problem to be solved by the application is solved by the following technical scheme:

[0006] In a first aspect, the application provides an aluminum scandium nitride film easy to peel off and high in crystalline quality, which comprises, from bottom to top, a sapphire substrate layer and a two-dimensional BN layer, and an AlScN layer is grown on the two-dimensional BN layer, and the AlScN layer is treated by a high-temperature annealing process.

[0007] Optionally, the thickness of the two-dimensional BN layer is 1-10 nm, and the thickness of the AlScN layer is 200 nm-2000 nm.

[0008] In a second aspect, the application provides a preparation method of an aluminum scandium nitride film easy to peel off and high in crystalline quality, which comprises:

[0009] Step 1: in an LPCVD reaction furnace, a copper foil substrate is heated and pretreated, and the heating temperature is 800-1200℃;

[0010] Step 2: a 1-10 nm thick two-dimensional BN layer is grown on the pretreated copper foil substrate by using an LPCVD method;

[0011] Step 3: a polymethyl methacrylate (PMMA) anisole solution is spin-coated on the surface of the two-dimensional BN layer, and then the copper foil substrate is removed by placing it in a Fecl3 solution, to obtain a two-dimensional BN layer covered with PMMA.

[0012] Step 4: transferring the two-dimensional BN layer covered by PMMA to a sapphire substrate, and removing the PMMA with an acetone solution and thermal oxidation-reduction to obtain a structure formed by the sapphire substrate and the two-dimensional BN film;

[0013] Step 5: growing an AlScN film with a thickness of 200 nm-2000 nm on the crystal structure formed by the sapphire substrate and the two-dimensional BN film by using a reactive sputtering method, an MOCVD method or an MBE method;

[0014] Step 6: performing high-temperature annealing treatment on the structure formed by the sapphire substrate, the two-dimensional BN layer and the AlScN film, the annealing temperature being 1200℃-1900℃, the annealing time being 10 min-20 h, and the annealing protective atmosphere being nitrogen;

[0015] Step 7: after the annealing process is completed, peeling off the AlScN film from the structure formed by the sapphire substrate, the two-dimensional BN layer and the AlScN film by using a tape to obtain a high-quality AlScN film.

[0016] Optionally, step 2 comprises:

[0017] The temperature of the tube furnace in the LPCVD device is increased from room temperature to 800-1200℃ at a temperature increasing rate of 10℃ / min, and the holding time is 40 min,

[0018] The pressure in the reaction chamber is maintained at 250-300 Torr,

[0019] The protective atmosphere is hydrogen, and the gas flow is 50-90 ml / min,

[0020] The two-dimensional BN layer with a thickness of 1-10 nm is grown on the pretreated copper foil substrate by using the LPCVD method.

[0021] Optionally, step 3 comprises:

[0022] The poly-methyl methacrylate (PMMA) benzyl ether solution with a PMMA mass content of 4.5% is spin-coated on the surface of the two-dimensional BN layer at a spin coater speed of 200-400 r / min for 20-40 s;

[0023] The copper foil substrate is removed by placing it in the Fecl3 solution with a concentration of 0.5-1.5 mol / L to obtain the two-dimensional BN layer covered by PMMA.

[0024] Optionally, step 4 comprises:

[0025] The two-dimensional BN layer covered by PMMA is transferred to a sapphire substrate;

[0026] The two-dimensional BN layer transferred to the sapphire substrate is dried at room temperature for 1-5h;

[0027] The two-dimensional BN layer transferred to the sapphire substrate after drying is put into an acetone solvent to remove the PMMA, and the PMMA is removed with an acetone solution and a hot oxidation-reduction, to obtain a structure formed by the sapphire substrate and the two-dimensional BN film;

[0028] The structure formed by the sapphire substrate and the two-dimensional BN film is heated to a temperature of 500-1000℃ and maintained for 5-30min.

[0029] Optionally, the process conditions for growing the AlScN film by the reactive sputtering method in step 5 are as follows:

[0030] The reaction chamber temperature is 800-1400℃,

[0031] The reaction chamber pressure is 20-300Torr;

[0032] The sputtering target is a scandium-doped aluminum alloy target, and the scandium atom content is 3%-30%.

[0033] Optionally, the process conditions for growing the AlScN film by the MOCVD method in step 5 are as follows:

[0034] The reaction chamber temperature is 800-1400℃,

[0035] The reaction chamber pressure is 20-300Torr;

[0036] The flow rates of TMAl and TMSc are 20-100ml / min and 10-80ml / min, respectively;

[0037] The reaction carrier gas is a mixed gas of hydrogen (H2) and nitrogen (N2);

[0038] The growth time is 60s.

[0039] Optionally, the process conditions for growing the AlScN film by the MBE method in step 5 are as follows:

[0040] The reaction chamber temperature is 200-800℃,

[0041] The reaction chamber pressure is 10-11-10-9Torr;

[0042] The source beam is divided into Al and Sc,

[0043] The reaction time is 2-10h,

[0044] Nitrogen (N2) is used as the protective atmosphere.

[0045] Optionally, the high-temperature annealing treatment of AlScN in step 6 has the following process conditions:

[0046] The annealing temperature is 1000-1900℃,

[0047] The annealing time is 2-8h,

[0048] The protective atmosphere is nitrogen, and the pressure is 20-300Torr.

[0049] The application provides an easily peelable high-crystalline-quality aluminum scandium nitrogen film, which comprises, from bottom to top, a sapphire substrate layer and a two-dimensional BN layer, wherein an AlScN layer is grown on the two-dimensional BN layer, and the AlScN layer is treated by a high-temperature annealing process.

[0050] The application provides a preparation method of the easily peelable high-crystalline-quality aluminum scandium nitrogen film, wherein a 1-10nm-thick two-dimensional BN layer is grown on a pretreated copper foil substrate by using an LPCVD method, and then the two-dimensional BN layer is transferred to a sapphire substrate, and an AlScN film is grown on the two-dimensional BN layer transferred to the sapphire substrate by using a sputtering method, so that the peelability is improved, and the material quality is improved by a high-temperature annealing process, and therefore the easily peelable high-crystalline-quality aluminum scandium nitrogen film can be used in a filter device.

[0051] The application will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 is a structure schematic diagram of the easily peelable high-quality aluminum scandium nitrogen film provided by the embodiment of the application;

[0053] Figure 2 is a flow schematic diagram of the preparation method of the easily peelable high-quality aluminum scandium nitrogen film provided by the embodiment of the application;

[0054] Figure 3 is a preparation process schematic diagram of the easily peelable high-quality aluminum scandium nitrogen film provided by the embodiment of the application. DETAILED DESCRIPTION

[0055] The application will be further described in detail below with reference to the drawings and embodiments.

[0056] As Figure 1As shown, the present invention provides an easily peelable aluminum scandium nitrogen thin film with high crystallinity, comprising, from bottom to top: a sapphire substrate layer and a two-dimensional BN layer, characterized in that an AlScN layer is sputtered on the two-dimensional BN layer, and the AlScN layer is treated by a high-temperature annealing process.

[0057] The thickness of the two-dimensional BN layer is 1-10 nm, and the thickness of the AlScN layer is 200 nm-2000 nm.

[0058] This invention provides an easily peelable, high-crystallinity aluminum scandium nitrogen (ASN) thin film, comprising, from bottom to top: a sapphire substrate layer and a two-dimensional BN layer. An AlScN layer is sputtered onto the two-dimensional BN layer, and the AlScN layer is treated by a high-temperature annealing process. This invention uses sputtering, MOCVD, or MBE methods to grow the AlScN thin film on the two-dimensional BN layer transferred to sapphire, improving peelability, and the high-temperature annealing process improves material quality. Therefore, the easily peelable, high-crystallinity aluminum scandium nitrogen (ASN) thin film of this invention can be used in filter devices.

[0059] like Figure 2 As shown, the method for preparing an easily peelable aluminum scandium nitrogen thin film with high crystallinity provided by the present invention includes:

[0060] Step 1: In the LPCVD reactor, the copper foil substrate is pretreated by heating at a temperature of 800-1200℃;

[0061] Step 2: Grow a 1-10 nm thick two-dimensional BN layer on the pretreated copper foil substrate using LPCVD;

[0062] Step 3: Spin-coat the surface of the two-dimensional BN layer with polymethyl methacrylate (PMMA) anisole solution, and then immerse it in FeCl3 solution to remove the copper foil substrate, thereby obtaining a two-dimensional BN layer covered with PMMA;

[0063] Step 4: Transfer the two-dimensional BN layer covered with PMMA to the sapphire substrate, and remove the PMMA with acetone solution and thermal redox to obtain the structure formed by the sapphire substrate and the two-dimensional BN film;

[0064] Step 5: On a sapphire substrate and a two-dimensional BN thin film crystal structure, an AlScN thin film with a thickness of 200 nm-2000 nm is grown using reactive sputtering, MOCVD, or MBE methods.

[0065] Step 6: The structure containing the sapphire substrate, the two-dimensional BN layer and the AlScN thin film is subjected to high-temperature annealing. The annealing temperature is 1200℃-1900℃, the annealing time is 10min-20h, and the annealing protective atmosphere is nitrogen.

[0066] Step 7: after the annealing process is completed, the AlScN film is peeled off using a tape on the structure comprising the sapphire substrate, the two-dimensional BN layer and the AlScN film, and a high-quality AlScN film is peeled off.

[0067] The application provides a preparation method of an easy-to-peel high-crystalline-quality aluminum scandium nitride film. A 1-10 nm thick two-dimensional BN layer is grown on a pretreated copper foil substrate by using an LPCVD method, and then is transferred to a sapphire substrate. An AlScN film is grown on the two-dimensional BN layer transferred to the sapphire substrate by using a sputtering method, an MOCVD method or an MBE method, the peelability is improved, and the material quality is improved through a high-temperature annealing process. Therefore, the easy-to-peel high-crystalline-quality aluminum scandium nitride film can be used in a filter device.

[0068] In an embodiment, step 2 comprises:

[0069] The temperature of the tube furnace in the LPCVD device is increased from room temperature to 800-1200℃ at a temperature increasing rate of 10℃ / min, and the holding time is 40 min,

[0070] The pressure in the reaction chamber is maintained at 250-300 Torr,

[0071] The protective atmosphere is hydrogen, and the gas flow is 50-90 ml / min,

[0072] A 1-10 nm thick two-dimensional BN layer is grown on the pretreated copper foil substrate by using an LPCVD method.

[0073] In an embodiment, step 3 comprises:

[0074] The two-dimensional BN layer is spin-coated with a 4.5% mass content of polymethyl methacrylate (PMMA) benzyl ether solution at a rotation speed of 200-400 r / min for 20-40 s;

[0075] The copper foil substrate is removed by placing the two-dimensional BN layer covered with PMMA in a Fecl3 solution with a concentration of 0.5-1.5 mol / L, and a two-dimensional BN layer covered with PMMA is obtained.

[0076] In an embodiment, step 4 comprises:

[0077] The two-dimensional BN layer covered with PMMA is transferred to a sapphire substrate;

[0078] The two-dimensional BN layer transferred to the sapphire substrate is dried at room temperature for 1-5 h;

[0079] The two-dimensional BN layer transferred to the sapphire substrate after drying is put into an acetone solvent to remove the PMMA, and the PMMA is removed by an acetone solution and a hot oxidation-reduction, to obtain a structure formed by the sapphire substrate and the two-dimensional BN thin film.

[0080] The structure formed by the sapphire substrate and the two-dimensional BN thin film is heated to a temperature of 500-1000℃ and kept for 5-30 min.

[0081] In an embodiment, the AlScN thin film is grown in step 5, and the process conditions are as follows:

[0082] The reaction chamber temperature is 800-1400℃,

[0083] The reaction chamber pressure is 200-300 Torr;

[0084] The sputtering target is a scandium-doped aluminum alloy target, and the content of scandium atoms is 3%-30%.

[0085] In an embodiment, the high-temperature annealing treatment of the AlScN in step 6 has the process conditions as follows:

[0086] The annealing temperature is 1000-1500℃,

[0087] The annealing time is 2-8 h,

[0088] The protective atmosphere is nitrogen, and the pressure is 200-300 Torr.

[0089] Referring to Figure 3 , the present application provides three embodiments for preparing a peelable high-quality aluminum nitride thin film, and the process is as follows:

[0090] The first embodiment uses a sputtering method to grow an AlScN thin film.

[0091] The precursor borane ammonia is placed on one side of the gas inlet end of the quartz tube in the tube furnace, and a copper foil is placed in the quartz tube in the furnace, as shown in (a) of Figure 3 , the mechanical pump and the gas inlet valve (the protective gas is hydrogen) are opened, the gas flow is 71 ml / min, the temperature of the tube furnace is raised from room temperature to 1000℃ at a rate of 10℃ / min, and the holding time is 40 min. After the borane ammonia gas sublimates, it is carried into the quartz tube by H2, and a two-dimensional BN thin film is deposited on the copper substrate.

[0092] The PMMA anisole solution (the mass content of PMMA in the solution is 4.5%) is spin-coated (the rotation speed of the spin coater is 300 r / min, and the rotation time is 30 s) on the copper foil on which the BN thin film is grown, to form a PMMA / BN / Cu structure, as shown in (b) of Figure 3 .

[0093] After drying for 2 min at room temperature, the sample was placed in FeCl3 solution (1 mol / L) until the copper was completely dissolved to obtain a transparent PMMA / BN structure film, as shown in Fig. 1(c). Figure 3 After being washed with deionized water for 2-3 times, the sample was transferred to a sapphire surface and dried for 2 h at room temperature, and then placed in an acetone solvent to remove the PMMA, to obtain a BN / sapphire structure, as shown in Fig. 1(d). Figure 3 The BN film on the sapphire surface was heated to a temperature of 800℃ and kept for 10 min to complete the heat treatment of the substrate wafer.

[0094] Scandium-doped aluminum nitride film was prepared on the pretreated substrate by a reactive sputtering process. The sputtering target was a scandium-doped aluminum alloy target with a scandium atomic content of 8%. Argon and nitrogen (purity of 99.9999%) were introduced into the cavity. The AlScN layer with a thickness of 1000 nm was grown under the process conditions of a reaction chamber temperature of 1200℃ and a pressure of 250 Torr, as shown in Fig. 1(e). Figure 3

[0095] The obtained sapphire / BN / AlScN was subjected to high-temperature heat annealing treatment. The annealing temperature was 1400℃, the annealing time was 4 h, and the protective atmosphere was nitrogen. An easy-to-peel high-quality AlScN film was obtained.

[0096] The annealed sapphire / BN / AlN film was used to peel off the AlN film using adhesive tape, as shown in Fig. 1(f). Figure 3

[0097] The second method is to grow an AlScN film using MOCVD.

[0098] The precursor borazane was placed at the gas inlet end of the quartz tube in the tube furnace, and the copper foil was placed in the quartz tube in the furnace, as shown in Fig. 1(a). The mechanical pump and gas inlet valve (protective gas is hydrogen) were opened. The gas flow was 71 ml / min. The temperature of the tube furnace was increased from room temperature to 1000℃ at a rate of 10℃ / min, and the holding time was 40 min. After the borazane gas sublimated, it was carried into the quartz tube by H2, and a two-dimensional BN film was deposited on the copper substrate. Figure 3

[0099] The PMMA anisole solution (PMMA mass content in the solution was 4.5%) was spin-coated (the rotation speed of the spin coater was 300 r / min, and the rotation time was 30 s) on the copper foil on which the BN film was grown on the surface to form a PMMA / BN / Cu structure, as shown in Fig. 1(b). Figure 3

[0100] After drying for 2 min at room temperature, the sample was placed in FeCl3 solution (1 mol / L) until the copper was completely dissolved to obtain a transparent PMMA / BN structure film, as shown in Fig. 1(c).​​​​Figure 3 The BN film was transferred to the sapphire surface after being washed with deionized water for 2-3 times, and then dried at room temperature for 2h, and then placed in an acetone solvent to remove the PMMA, to obtain a BN / sapphire structure, as shown in Figure 3 The BN film on the sapphire surface was heated to a temperature of 800℃ and kept for 10min to complete the heat treatment of the substrate wafer.

[0101] The AlScN film was grown on the pretreated substrate by MOCVD process, the reaction chamber temperature was 1000℃, trimethylaluminum (TMAl), trimethylscandium (TMSc) and ammonia (NH3) were introduced, the NH3flow rate was kept at 6000ml / min, the TMAl flow rate and the TMSc flow rate were 50ml / min and 30ml / min respectively, the reaction chamber pressure was 100Torr, the reaction carrier gas was a mixed gas of hydrogen (H2) and nitrogen (N2), and the growth time was 60s. An AlScN layer with a thickness of 1000nm was grown, as shown in Figure 3 (e).

[0102] The obtained sapphire / BN / AlScN was subjected to high-temperature heat annealing treatment, the annealing temperature was 1400℃, the annealing time was 4h, and the protective atmosphere was nitrogen. An easy-to-peel high-quality AlScN film was obtained.

[0103] The annealed sapphire / BN / AlN film was used to peel off the AlN film using adhesive tape, as shown in Figure 3 (f).

[0104] The third method is to grow an AlScN film using an MBE method.

[0105] The precursor borazane was placed at the gas inlet end of the quartz tube in the tube furnace, and the copper foil was placed in the quartz tube in the furnace, as shown in Figure 3 (a), the mechanical pump and the gas inlet valve (the protective gas was hydrogen) were turned on, the gas flow rate was 71ml / min, the tube furnace temperature was increased from room temperature to 1000℃ at a rate of 10℃ / min, and the holding time was 40min. After the borazane gas sublimated, it was carried into the quartz tube by H2, and a two-dimensional BN film was deposited on the copper substrate.

[0106] The PMMA / anisole solution (the PMMA mass content in the solution was 4.5%) was spin-coated (the rotation speed of the spin coater was 300r / min, and the rotation time was 30s) on the copper foil on which the BN film was grown, to form a PMMA / BN / Cu structure, as shown in Figure 3 (b).

[0107] After drying at room temperature for 2 min, the FeCl3 (the concentration of FeCl3 is 1 mol / L solution) is put in to dissolve the copper completely to obtain a transparent film of PMMA / BN structure, as shown in Fig. 1 (c). Figure 3 After washing with deionized water for 2-3 times, it is transferred to a sapphire surface, dried at room temperature for 2 h, and then put into an acetone solvent to remove PMMA, obtaining a BN / sapphire structure, as shown in Fig. 1 (d). Figure 3 The BN film on the sapphire surface is heated to a temperature of 800℃ and kept for 10 min to complete the heat treatment of the substrate wafer.

[0108] The scandium-doped aluminum nitride film is prepared on the pretreated substrate by an MBE process, the source beams are Al and Sc, the reaction chamber temperature is 650℃, the pressure is 10 -10 Torr, nitrogen (N2) is used as the protective atmosphere, and the reaction time is 5 h, and an AlScN layer with a thickness of 1000 nm is grown, as shown in Fig. 1 (e). Figure 3

[0109] The obtained sapphire / BN / AlScN is subjected to high-temperature annealing treatment, the annealing temperature is 1400℃, the annealing time is 4 h, and the protective atmosphere is nitrogen. An easy-to-peel high-quality AlScN film is obtained.

[0110] The annealed sapphire / BN / AlN film is peeled off to obtain an AlN film using adhesive tape, as shown in Fig. 1 (f). Figure 3

[0111] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present application, and all of them should be considered as falling within the protection scope of the present application.​​

Claims

1. A high crystalline quality, easily peelable aluminum scandium nitride film, comprising, from bottom to top: The sapphire substrate layer and the two-dimensional BN layer are characterized in that an AlScN layer is grown on the two-dimensional BN layer, and the AlScN layer is treated by a high-temperature annealing process; the aluminum scandium nitride film is applied to a filter device, the high-temperature annealing temperature is 1200-1900 DEG C, the annealing time is 10 min-20 h, and the annealing protective atmosphere is nitrogen; the thickness of the two-dimensional BN layer is 1-10 nm, and the thickness of the AlScN layer is 200-2000 nm.

2. A method for preparing an easily peelable high-crystalline quality aluminum scandium nitride film, characterized by, The aluminum scandium nitride film is prepared according to the method comprising: Step 1: heating and pretreating a copper foil substrate in an LPCVD reaction furnace, and the heating temperature is 800-1200 DEG C; Step 2: growing a two-dimensional BN layer with a thickness of 1-10 nm on the pretreated copper foil substrate by using an LPCVD method; Step 3: spin-coating a polymethyl methacrylate (PMMA) anisole solution on the surface of the two-dimensional BN layer, and then placing the two-dimensional BN layer in an Fecl3 solution to remove the copper foil substrate, so as to obtain a two-dimensional BN layer covered with PMMA; Step 4: transferring the two-dimensional BN layer covered with PMMA to a sapphire substrate, and removing the PMMA by using an acetone solution and a thermal oxidation-reduction method, so as to obtain a structure formed by the sapphire substrate and the two-dimensional BN film; Step 5: growing an AlScN film with a thickness of 200-2000 nm on the structure formed by the sapphire substrate and the two-dimensional BN film by using a reactive sputtering method, an MOCVD method or an MBE method; Step 6: performing high-temperature annealing treatment on the structure formed by the sapphire substrate, the two-dimensional BN layer and the AlScN film, the annealing temperature is 1200-1900 DEG C, the annealing time is 10 min-20 h, and the annealing protective atmosphere is nitrogen; Step 7: after the annealing process is completed, peeling off the AlScN film from the structure formed by the sapphire substrate, the two-dimensional BN layer and the AlScN film by using a tape, so as to obtain a high-quality AlScN film.

3. The production method according to claim 2, characterized by, The step 2 comprises: increasing the temperature of a tube furnace in an LPCVD device from room temperature to 800-1200 DEG C at a temperature increasing rate of 10 DEG C / min, and the holding time is 40 min, maintaining the pressure in a reaction chamber at 250-300 Torr, the protective atmosphere is hydrogen, and the gas flow is 50-90 ml / min, growing a two-dimensional BN layer with a thickness of 1-10 nm on the pretreated copper foil substrate by using an LPCVD method.

4. The method of claim 2, wherein, The step 3 comprises: spin-coating a polymethyl methacrylate (PMMA) anisole solution with a PMMA mass content of 4.5% on the surface of the two-dimensional BN layer at a rotation speed of 200-400 r / min for 20-40 s; then placing the two-dimensional BN layer in an Fecl3 solution with a concentration of 0.5-1.5 mol / L to remove the copper foil substrate, so as to obtain a two-dimensional BN layer covered with PMMA.

5. The method of claim 2, wherein, The step 4 comprises: transferring the two-dimensional BN layer covered with PMMA to a sapphire substrate; drying the two-dimensional BN layer transferred to the sapphire substrate at room temperature for 1-5 h; The two-dimensional BN layer transferred to the sapphire substrate after drying is put into an acetone solvent to remove the PMMA, and the PMMA is removed by using an acetone solution and thermal oxidation and reduction, to obtain a structure formed by the sapphire substrate and the two-dimensional BN thin film; The structure formed by the sapphire substrate and the two-dimensional BN thin film is heated to a temperature of 500-1000℃ and kept for 5-30 min.

6. The preparation method according to claim 2, characterized in that, The process conditions for growing the AlScN thin film by the reaction sputtering method in step 5 are as follows: The reaction chamber temperature is 800-1400℃, The reaction chamber pressure is 20-300 Torr; The sputtering target is a scandium-doped aluminum alloy target, and the scandium atom content is 3%-30%.

7. The preparation method according to claim 3, characterized in that, The process conditions for growing the AlScN thin film by the MOCVD method in step 5 are as follows: The reaction chamber temperature is 800-1400℃, The reaction chamber pressure is 20-300 Torr; The TMAl flow rate and the TMSc flow rate are 20-100 ml / min and 10-80 ml / min, respectively; The reaction carrier gas is a mixed gas of hydrogen (H2) and nitrogen (N2); The growth time is 60 s.

8. The preparation method according to claim 3, characterized in that, The process conditions for growing the AlScN thin film by the MBE method in step 5 are as follows: The reaction chamber temperature is 200-800℃, The reaction chamber pressure is 10-11-10-9 Torr; The source beam current is divided into Al and Sc, The reaction time is 2-10 h, Nitrogen (N2) is used as the protective atmosphere.

9. The preparation method according to claim 2, characterized in that, The process conditions for the high-temperature annealing treatment of the AlScN in step 6 are as follows: The annealing temperature is 1000-1900℃, The annealing time is 2-8 h, The protective atmosphere is nitrogen, and the pressure is 20-300 Torr.

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