Nitride thin film, remote epitaxy method thereof and semiconductor device

Abstract

The invention discloses a nitride film, a remote epitaxial method thereof and a semiconductor device, and the method comprises the following steps: covering a substrate with graphene, and guaranteeing that the relative rotation angle between the graphene and the substrate is 0 + / -0.1 degree; performing remote epitaxial growth of a nitride film on the graphene; the crystal structure of the substrate has an m surface, the crystal structure of the graphene has an m surface, and when the m surfaces of the substrate and the graphene are parallel to each other, the relative rotation angle between the graphene and the substrate is 0 + / -0.1 degree; and the m plane is a crystal plane of which the Miller index is (10-10) in the crystal structure. According to the remote epitaxial method of the nitride film, the relative rotation angle between the graphene and the substrate is controlled to be 0 + / -0.1 degrees, and the interaction between the graphene and the substrate is enhanced, so that high-quality remote epitaxial growth is realized, and the problem of poor growth quality of a remote epitaxial layer in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of remote epitaxy and third-generation semiconductor materials, and in particular to a remote epitaxy method for a nitride film, a nitride film prepared by the method, and a semiconductor device comprising the nitride film. Background Art

[0002] Gallium nitride (GaN), as a representative of the third generation wide bandgap semiconductor materials, has a direct bandgap of 3.4eV, a breakdown field strength of up to 3.3MV / cm, and a 6 Excellent physical properties, such as an electron saturation drift velocity of 100000 cm² / (V·s), make GaN irreplaceable in high-efficiency optoelectronic devices and high-power electronic devices. For example, industrial applications have been achieved in blue / white LEDs and laser diodes (LDs). In power electronics, GaN-based HEMT devices, with their advantages of high frequency and low conduction loss, are gradually replacing traditional silicon-based power devices.

[0003] Remote epitaxy (REPE) is an important technology for growing high-quality epitaxial layers on substrate surfaces, with broad application prospects in semiconductor devices, optoelectronics, and other fields. During the REPE process, the interface properties between the substrate and the epitaxial layer have a crucial impact on the quality and performance of the resulting epitaxial layer.

[0004] Graphene is widely used in various material systems due to its unique physical and chemical properties, such as excellent electrical performance, high mechanical strength, and good chemical stability. However, existing research has largely failed to fully consider the impact of the angle between graphene and the substrate on remote epitaxy. This leads to problems such as large lattice mismatch, numerous defects, and uneven growth in epitaxial layers, making it difficult to meet the high-quality epitaxial layer requirements of high-end device manufacturing.

[0005] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed before the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of this application. Summary of the Invention

[0006] In view of this, the present invention provides an improved remote epitaxial growth method for nitride thin films, which effectively solves the existing technical problems and can produce higher quality nitride thin films.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: A remote epitaxial growth method for a nitride thin film comprises the following steps: Cover the graphene on the substrate, ensuring that the relative angle between the graphene and the substrate is 0±0.1°; remote epitaxial growth of a nitride film on the graphene; The substrate has an m-plane in its crystal structure, and the graphene has an m-plane in its crystal structure. When the m-planes of the two are parallel to each other, the relative rotation angle between the graphene and the substrate is 0±0.1°; the m-plane is a crystal plane with a Miller index of (10-10) in the crystal structure.

[0008] It is preferred to ensure that the crystal structures of the two are completely parallel and to achieve a relative rotation angle of strictly 0°±θ (θ is an extremely small angle, θ≤0.1°), that is, to try to ensure that the relative rotation angle between the graphene and the substrate is 0°.

[0009] According to some preferred embodiments of the present invention, the substrate is an AlN substrate or a GaN substrate; the graphene is a single-layer graphene or a multi-layer graphene. In the case of multi-layer graphene, the relative rotation angle between each graphene layer and the substrate is 0±0.1°. The multi-layer graphene has no more than two layers, i.e., the graphene is preferably a single-layer graphene or a double-layer graphene, and more preferably a single-layer graphene.

[0010] According to some preferred embodiments of the present invention, when covering the graphene on the substrate, the graphene is first grown on the metal substrate by chemical vapor deposition. After the growth is completed, a layer of polymethyl methacrylate (PMMA) is spin-coated on the surface of the graphene as a transfer medium, and then the metal substrate is removed to obtain a PMMA-graphene film. Thereafter, the PMMA-graphene film is transferred and covered on the substrate.

[0011] According to some preferred embodiments of the present invention, transferring and covering the PMMA-graphene film onto the substrate specifically includes the following steps: Using a micromanipulation system, the PMMA-graphene film is aligned with the substrate to ensure that the m-plane in the crystal structure of the substrate and the m-plane in the crystal structure of the graphene are parallel to each other, so that the relative rotation angle between the graphene and the substrate is 0±0.1°; then, the PMMA-graphene film is covered on the substrate, with one side of the graphene close to the substrate, and the graphene and the substrate are tightly adhered by heating; then, the transferred sample is placed in a solvent to dissolve and remove the PMMA, thereby obtaining a graphene / substrate material with a relative rotation angle of 0±0.1°.

[0012] Preferably, the heating temperature is 90-110° C. and the heating time is 30-60 min. During heating, the substrate and the graphene undergo differential thermal expansion, which makes the expansion of the two complementary, reduces the gap, and makes the graphene fit tightly to the substrate.

[0013] In some embodiments of the present invention, the PMMA-graphene film is aligned with the substrate to ensure that the m-plane in the crystal structure of the substrate and the m-plane in the crystal structure of the graphene are parallel to each other, which is specifically achieved by the following steps: Using the edge of the substrate's m-plane (10-10) as a positioning reference, a crystal orientation reference mark is etched on the substrate; Before spin-coating PMMA on the graphene surface, the zigzag edge (m-plane) of the graphene on the metal substrate is identified and directional marks are etched on the graphene using the m-plane (10-10) edge of the graphene as a positioning reference. Using a micromanipulation system, the crystal orientation reference mark on the substrate is aligned with the center of the directional mark on the graphene; Under 532nm laser irradiation, the polarized reflection images of the substrate and graphene were collected respectively; the crystallographic periodic signals of the two were extracted through Fourier transform, and the signal phase difference was confirmed to be ≤0.02°, completing the final alignment.

[0014] According to some preferred embodiments of the present invention, before covering the substrate with graphene, the substrate is pretreated: the substrate is sequentially placed in an acetone solution and an ethanol solution for ultrasonic cleaning, then rinsed with deionized water, and finally dried.

[0015] According to some preferred implementation aspects of the present invention, the material of the nitride film is gallium nitride, and the remote epitaxial growth of the nitride film comprises the following steps: At a temperature of 800-1000°C, a nitrogen source with a flow rate of 2500-3500 sccm, a gallium source with a flow rate of 10-30 sccm, and a carrier gas are introduced for 10-30 minutes to grow a nucleation layer; Under the condition of a temperature of 800-1200° C., introducing a nitrogen source with a flow rate of 4000-6000 sccm, a gallium source with a flow rate of 20-40 sccm, and a carrier gas, and reacting for 70-110 minutes to grow a thin film layer on the nucleation layer to obtain the nitride thin film; The carrier gas includes nitrogen with a flow rate of 100 sccm-300 sccm and hydrogen with a flow rate of 20 sccm-40 sccm.

[0016] According to some preferred embodiments of the present invention, the nitride film with a thickness of 3 μm prepared by the remote epitaxy method has a dislocation density of less than or equal to 9×10 7 cm -2 .

[0017] The present invention also provides a nitride film prepared by the above method and a semiconductor device including the nitride film.

[0018] Due to the application of the above-mentioned technical solution, the present invention has the following advantages compared with the prior art: the remote epitaxial growth method of the nitride film of the present invention controls the relative rotation angle between the graphene and the substrate to 0±0.1°, thereby enhancing the interaction between the two, thereby achieving high-quality remote epitaxial growth, and solving the problem of poor growth quality of the remote epitaxial layer in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 A schematic flow chart of a remote epitaxial growth method for a nitride thin film according to an embodiment of the present invention; Figure 2 A schematic diagram of an m-plane in a substrate crystal structure provided by an embodiment of the present invention; Figure 3 A schematic diagram of the a-plane in the substrate crystal structure provided by an embodiment of the present invention; Figure 4 A schematic diagram of the m-plane and a-plane in the graphene crystal structure provided by an embodiment of the present invention; Figure 5 Schematic diagram of an embodiment of the present invention when the relative rotation angle between the graphene and the substrate is 0; Figure 6 Schematic diagram of graphene when it is rotated at different angles; Figure 7 is the interface binding energy between graphene and substrate at different rotation angles (the box is the top view of the heterojunction); Figure 8 is the charge transfer amount of graphene at different rotation angles; Figure 9 is the distance between graphene and substrate at different rotation angles (the box is the main view of the heterojunction). DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0022] The present invention provides a method for remote epitaxial growth of a GaN epitaxial layer on graphene without a corner with the substrate, optimizing the interaction between the graphene and the substrate, thereby improving the quality of remote epitaxial growth. The remote epitaxial growth method of the nitride film of the present invention comprises the following steps: Cover the graphene on the substrate, ensuring that the relative angle between the graphene and the substrate is 0±0.1°; Remote epitaxial growth of nitride thin films on graphene.

[0023] It is preferred to ensure that the crystal structures of the two are completely parallel and to achieve a relative rotation angle of strictly 0°±θ (θ is an extremely small angle, θ≤0.1°), that is, to try to ensure that the relative rotation angle between the graphene and the substrate is 0°.

[0024] The substrate is an AlN substrate or a GaN substrate; the graphene is a single-layer graphene or a multi-layer graphene. In the case of multi-layer graphene, the relative rotation angle between each graphene layer and the substrate is 0±0.1°. Preferably, the substrate is an AlN substrate; the multi-layer graphene has no more than two layers, preferably a single-layer graphene or a double-layer graphene, and more preferably a single-layer graphene.

[0025] like Figures 2 to 5 As shown, the crystal structure of the substrate has an m-plane ( Figure 2 ) and side a ( Figure 3 ), graphene has an m-plane and an a-plane in its crystal structure ( Figure 4 When the relative rotation angle between graphene and the substrate is 0, that is, the m-plane in the crystal structure of the substrate and the m-plane in the crystal structure of graphene are parallel to each other, and the a-plane in the crystal structure of the substrate and the a-plane in the crystal structure of graphene are parallel to each other ( Figure 5 ). Figure 5 This represents an ideal state. In reality, the annular crystal structure of graphene is not necessarily located exactly within the annular crystal structure of the substrate; rather, it may be offset. This is sufficient as long as the m-planes in the substrate's crystal structure and the graphene's crystal structure are parallel to each other. In this invention, the m-plane is a plane with a Miller index of (10-10) in the crystal structure, and the a-plane is a plane with a Miller index of (11-20) in the crystal structure.

[0026] like Figure 1 As shown, the remote epitaxial growth method of the nitride thin film of the present invention specifically includes the following steps: S1. Substrate pretreatment.

[0027] Select a suitable substrate material, such as aluminum nitride (AlN) substrate.

[0028] The substrate is cleaned to remove surface impurities and oxides. The specific cleaning process can be ultrasonic cleaning with an organic solvent (such as acetone or ethanol), followed by rinsing with deionized water. Finally, the surface moisture is removed by drying to obtain a clean substrate surface, providing a good foundation for subsequent graphene transfer and epitaxial growth.

[0029] S2. Graphene preparation.

[0030] Chemical vapor deposition (CVD) is used to grow high-quality single-layer graphene on metal substrates (such as copper foil). Controlling various CVD growth process parameters, such as reaction temperature, gas flow rate, and growth time, yields large, defect-free graphene films.

[0031] After the growth is completed, the graphene is transferred from the metal substrate through a wet transfer process. During the transfer process, a suitable transfer medium (such as polymethyl methacrylate, PMMA) is used to avoid damage to the graphene.

[0032] Specifically, when graphene is covered on a substrate, a single layer of graphene is first grown on a metal substrate using chemical vapor deposition. After the growth is completed, a layer of polymethyl methacrylate is spin-coated on the surface of the graphene as a transfer medium. The metal substrate is then removed to obtain a PMMA-graphene film, which is then transferred and covered on the substrate.

[0033] S3, corner-free graphene transfer.

[0034] Using high-precision alignment equipment, such as a micromanipulation system (optical microscope combined with a micromanipulation platform), the prepared graphene is precisely aligned with the substrate to ensure that the relative rotation angle between the graphene and the substrate is 0±0.1°.

[0035] During the transfer process, mild transfer conditions are adopted, such as controlling the transfer temperature, to avoid wrinkling, damage of graphene or unnecessary stress between the graphene and the substrate due to excessive temperature, ensuring that the graphene fits tightly to the substrate without corner deviation.

[0036] Preferably, transferring and covering the PMMA-graphene film onto the substrate specifically comprises the following steps: Using a micromanipulation system, the PMMA-graphene film is aligned with the substrate, ensuring that the m-plane in the crystal structure of the substrate and the m-plane in the crystal structure of the graphene are parallel to each other, so that the relative rotation angle between the graphene and the substrate is 0±0.1°; then the PMMA-graphene film is covered on the substrate, with the graphene side close to the substrate, and the graphene and substrate are tightly fitted by heating; then the transferred sample is placed in a solvent to dissolve and remove the PMMA, obtaining a graphene / substrate material with a relative rotation angle of 0±0.1°.

[0037] Acetone is a preferred solvent for dissolving and removing PMMA. The surface tension of acetone is much smaller than the graphene-substrate adsorption energy. Moreover, the acetone dissolution of PMMA generates almost no torque, which can better ensure that the graphene does not separate from the substrate and does not change the rotation angle.

[0038] The preferred heating temperature is 90-110° C. and the heating time is 30-60 minutes. During heating, the substrate and graphene undergo differential thermal expansion, which makes the expansion of the two complementary, reduces the gap, and makes the graphene and substrate fit tightly.

[0039] In some embodiments, the PMMA-graphene film is aligned with the substrate to ensure that the m-plane in the crystal structure of the substrate and the m-plane in the crystal structure of the graphene are parallel to each other, which is achieved by the following steps: Using the edge of the substrate's m-plane (10-10) as a positioning reference, a crystal orientation reference mark is etched on the substrate; Before spin-coating PMMA on the graphene surface, the zigzag edge (m-plane) of the graphene on the metal substrate is identified and directional marks are etched on the graphene using the m-plane (10-10) edge of the graphene as a positioning reference. Using a micromanipulation system, the crystal orientation reference mark on the substrate is aligned with the center of the directional mark on the graphene; Under 532nm laser irradiation, the polarized reflection images of the substrate and graphene were collected respectively; the crystallographic periodic signals of the two were extracted through Fourier transform, and the signal phase difference was confirmed to be ≤0.02°, completing the final alignment.

[0040] S4. Remote epitaxial growth.

[0041] The substrate to which the corner-free graphene has been transferred is placed in an epitaxial growth device (such as MOCVD) for remote epitaxial growth under appropriate growth conditions. Based on the characteristics of the target epitaxial material, parameters such as temperature, gas flow rate, and growth time are precisely controlled to ensure that the epitaxial material grows on the corner-free graphene and substrate system.

[0042] Preferably, the material of the nitride film is gallium nitride, and the remote epitaxial growth of the nitride film includes the following steps: At a temperature of 800-1000°C, a nitrogen source with a flow rate of 2500-3500 sccm, a gallium source with a flow rate of 10-30 sccm, and a carrier gas are introduced for 10-30 minutes to grow a nucleation layer; Under the condition of a temperature of 800-1200° C., a nitrogen source with a flow rate of 4000-6000 sccm, a gallium source with a flow rate of 20-40 sccm, and a carrier gas are introduced, and the reaction is carried out for 70-110 minutes to grow a thin film layer on the nucleation layer to obtain a nitride thin film; The carrier gas includes nitrogen with a flow rate of 100 sccm-300 sccm and hydrogen with a flow rate of 20 sccm-40 sccm.

[0043] The 3 μm thick nitride film prepared by the remote epitaxy method has a dislocation density less than or equal to 9×10 7 cm -2 At the same time, the nitride film prepared by the above method can be applied to semiconductor devices.

[0044] In some embodiments of the present invention, the remote epitaxial growth method of a nitride film specifically includes the following steps: S1. Substrate pretreatment.

[0045] An AlN substrate was selected and first placed in an acetone solution for ultrasonic cleaning for 10-20 minutes to remove surface particulate impurities; then placed in an ethanol solution for ultrasonic cleaning for 10-20 minutes to further clean the surface; then the substrate was rinsed with deionized water multiple times to remove residual organic solvent; finally, the substrate was placed in a drying oven and dried at 70-90°C for 20-40 minutes to obtain a clean substrate surface.

[0046] S2. Graphene preparation.

[0047] Single-layer graphene is grown on a copper foil substrate using the CVD method. The copper foil is placed in a CVD apparatus and heated to 900-1100°C under argon protection. Hydrogen (at a flow rate of 40-60 sccm) and methane (at a flow rate of 8-12 sccm) are then introduced for 25-35 minutes to produce a high-quality single-layer graphene on the copper foil surface.

[0048] After growth is complete, a 90-110nm thick layer of polymethyl methacrylate (PMMA) is spin-coated on the graphene surface as a transfer medium. The copper foil with the PMMA-graphene layer is then placed in a ferric chloride solution to etch away the copper foil, leaving a PMMA-graphene film suspended in the solution. The PMMA-graphene film is then rinsed multiple times with deionized water to remove any residual etching solution.

[0049] S3, corner-free graphene transfer.

[0050] Using a micromanipulation system (optical microscope combined with a micromanipulation platform), the prepared PMMA-graphene film was precisely aligned with the pre-treated AlN substrate, ensuring that the relative rotation angle between the graphene and the substrate was 0±0.1°.

[0051] The PMMA-graphene film is then slowly transferred to the AlN substrate, with the graphene side close to the substrate, and heated (temperature controlled at 90-110°C) to make the graphene and substrate fit tightly together.

[0052] The transferred sample was then placed in an acetone solution to dissolve and remove the PMMA, obtaining a corner-free graphene / AlN substrate.

[0053] Step S3 of transferring the corner-free graphene specifically includes the following steps: S31, substrate crystal orientation mark.

[0054] After the pretreatment in step S1 , a crystal orientation reference mark is formed on the surface of the AlN substrate using a focused ion beam (FIB).

[0055] Specifically, the edge of the m-plane (10-10) of the substrate is selected as a positioning reference, and three groups of cross-shaped marks (line width 2 μm, depth 50 nm) with an interval of 100 μm are etched on the substrate, as shown in FIG. Figure 5 As shown, one of the cross marks is parallel to the substrate m-plane of the positioning reference.

[0056] S32, graphene crystal orientation marking.

[0057] Before spin coating PMMA on the graphene surface in step S2, electron beam lithography (EBL) is used to make directional marks corresponding to the edges of the graphene m-plane.

[0058] Specifically, the zigzag edge (m-plane) of graphene on the metal substrate (copper foil) is identified, and two parallel straight line marks (line width 1 μm, length 50 μm) are etched along the edge direction, with a line spacing of 30 μm, and the parallelism deviation between the mark and the zigzag edge is ≤ 0.03°, such as Figure 5 As shown, the straight line mark is parallel to the graphene m-plane.

[0059] S33, step-by-step alignment operation.

[0060] 1) Coarse alignment (±1° range).

[0061] By identifying the cross mark on the substrate and the straight mark on the graphene, the XY axis translation of the platform in the micromanipulation system is adjusted so that the center deviation between the two is ≤50μm, and the platform is rotated so that the angle between the mark lines is ≤1°. 2) Precision alignment (±0.1° range).

[0062] Switch the micromanipulator to 1000× magnification. Using the substrate's m-plane marking (crystal orientation reference mark) as a reference, use the micromanipulator's piezoelectric rotation stage to perform step adjustments (0.005° steps) to monitor the angle between the graphene marking (directional marker) and the substrate marking (crystal orientation reference mark) in real time. Lock the micromanipulator's rotation axis when the angle is ≤0.05°.

[0063] S34, crystallographic orientation verification.

[0064] Using the polarizing microscope module of the micromanipulation system, polarized reflection images of the substrate and graphene were collected under 532nm laser illumination. Crystallographic periodic signals (e.g., 0.311nm for the AlN m-plane period and 0.246nm for the graphene sawtooth edge period) were extracted using Fourier transform. The phase difference between the signals was confirmed to be ≤0.02°, completing the final alignment.

[0065] S35. Transfer.

[0066] After alignment is completed, the PMMA-graphene film is slowly transferred to the AlN substrate.

[0067] S4. Remote epitaxial growth.

[0068] The AlN substrate with the corner-free graphene transferred is placed in the MOCVD equipment.

[0069] Growth is performed at a temperature of 700-900°C, with an ammonia flow rate of 2500-3500 sccm, a TMGa flow rate of 15-25 sccm, and a carrier gas mixture of 150-250 sccm nitrogen and 25-35 sccm hydrogen for 15-25 minutes. Growth is performed at a temperature of 900-1100°C, with an ammonia flow rate of 4500-5500 sccm, a TMGa flow rate of 25-35 sccm, and a carrier gas mixture of 250-350 sccm nitrogen and 35-45 sccm hydrogen for 80-100 minutes.

[0070] Finally, a 3 μm GaN film was obtained, and the dislocation density of the film was less than or equal to 9×10 7 cm -2 .

[0071] Example 1: In this example, the remote epitaxial growth method of a nitride thin film specifically includes the following steps: S1. Substrate pretreatment.

[0072] An AlN substrate was selected. The substrate was first placed in an acetone solution for ultrasonic cleaning for 15 minutes to remove surface particulate impurities; then it was placed in an ethanol solution for ultrasonic cleaning for 15 minutes to further clean the surface; then the substrate was rinsed with deionized water multiple times to remove residual organic solvent; finally, the substrate was placed in a drying oven and dried at 80°C for 30 minutes to obtain a clean substrate surface.

[0073] S2. Graphene preparation.

[0074] A single layer of graphene was grown on a copper foil substrate using CVD. The copper foil was placed in a CVD apparatus and heated to 1000°C under argon protection. Hydrogen (at a flow rate of 50 sccm) and methane (at a flow rate of 10 sccm) were then introduced for 30 minutes, resulting in the growth of high-quality single-layer graphene on the copper foil surface.

[0075] After growth is complete, a layer of polymethyl methacrylate (PMMA) is spin-coated on the graphene surface to a thickness of approximately 100 nm as a transfer medium. The copper foil with the PMMA-graphene layer is then placed in a ferric chloride solution to etch away the copper foil, leaving a PMMA-graphene film suspended in the solution. The PMMA-graphene film is then rinsed multiple times with deionized water to remove any residual etching solution.

[0076] S3, corner-free graphene transfer.

[0077] According to the above steps S31-S35, the prepared PMMA-graphene film is precisely aligned with the pre-treated AlN substrate using a micromanipulation system to ensure that the relative rotation angle between the graphene and the substrate is 0±0.1°.

[0078] The PMMA-graphene film is then slowly transferred to the AlN substrate, with the graphene side close to the substrate, and heated (the temperature is controlled at 100°C) to make the graphene and substrate fit tightly together.

[0079] The transferred sample was then placed in an acetone solution to dissolve and remove the PMMA, obtaining a corner-free graphene / AlN substrate.

[0080] S4. Remote epitaxial growth.

[0081] The AlN substrate, upon which the corner-free graphene had been transferred, was placed in an MOCVD apparatus. Growth was continued for 20 minutes at a growth temperature of 800°C, with a flow rate of 3000 sccm of ammonia, 20 sccm of TMGa, and a carrier gas mixture of 200 sccm of nitrogen and 30 sccm of hydrogen. Growth was continued for 90 minutes at a growth temperature of 1000°C, with a flow rate of 5000 sccm of ammonia, 30 sccm of TMGa, and a carrier gas mixture of 300 sccm of nitrogen and 40 sccm of hydrogen.

[0082] Finally, a 3 μm GaN film was obtained with a dislocation density of 5×10 7 cm -2 .

[0083] Example 2: In this example, the remote epitaxial growth method of a nitride film specifically includes the following steps: S1. Substrate pretreatment.

[0084] An AlN substrate was selected. The substrate was first placed in an acetone solution for ultrasonic cleaning for 10 minutes to remove surface particulate impurities; then it was placed in an ethanol solution for ultrasonic cleaning for 20 minutes to further clean the surface; then the substrate was rinsed with deionized water multiple times to remove residual organic solvent; finally, the substrate was placed in a drying oven and dried at 90°C for 20 minutes to obtain a clean substrate surface.

[0085] S2. Graphene preparation.

[0086] A single layer of graphene was grown on a copper foil substrate using CVD. The copper foil was placed in a CVD apparatus and heated to 1100°C under argon protection. Hydrogen (at a flow rate of 40 sccm) and methane (at a flow rate of 8 sccm) were then introduced for 35 minutes, resulting in the growth of high-quality single-layer graphene on the copper foil surface.

[0087] After growth is complete, a layer of polymethyl methacrylate (PMMA) is spin-coated on the graphene surface to a thickness of approximately 110 nm as a transfer medium. The copper foil with the PMMA-graphene layer is then placed in a ferric chloride solution to etch away the copper foil, leaving a PMMA-graphene film suspended in the solution. The PMMA-graphene film is then rinsed multiple times with deionized water to remove any residual etching solution.

[0088] S3, corner-free graphene transfer.

[0089] According to the above steps S31-S35, the prepared PMMA-graphene film is precisely aligned with the pre-treated AlN substrate using a micromanipulation system to ensure that the relative rotation angle between the graphene and the substrate is 0±0.1°.

[0090] The PMMA-graphene film is then slowly transferred to the AlN substrate, with the graphene side close to the substrate, and heated (the temperature is controlled at 110°C) to make the graphene and substrate fit tightly together.

[0091] The transferred sample was then placed in an acetone solution to dissolve and remove the PMMA, obtaining a corner-free graphene / AlN substrate.

[0092] S4. Remote epitaxial growth.

[0093] The AlN substrate, upon which the corner-free graphene had been transferred, was placed in an MOCVD apparatus. Growth was carried out for 25 minutes at a growth temperature of 900°C, with a flow rate of 2500 sccm of ammonia, 15 sccm of TMGa, and a carrier gas mixture of 150 sccm of nitrogen and 25 sccm of hydrogen. Growth was then continued for 100 minutes at a growth temperature of 1100°C, with a flow rate of 4500 sccm of ammonia, 25 sccm of TMGa, and a carrier gas mixture of 250 sccm of nitrogen and 35 sccm of hydrogen.

[0094] Finally, a 3 μm GaN film was obtained with a dislocation density of 9×10 7 cm -2 .

[0095] Example 3: In this example, the remote epitaxial growth method of a nitride film specifically includes the following steps: S1. Substrate pretreatment.

[0096] An AlN substrate was selected. The substrate was first placed in an acetone solution for ultrasonic cleaning for 20 minutes to remove surface particulate impurities; then it was placed in an ethanol solution for ultrasonic cleaning for 11 minutes to further clean the surface; then the substrate was rinsed with deionized water multiple times to remove residual organic solvent; finally, the substrate was placed in a drying oven and dried at 70°C for 40 minutes to obtain a clean substrate surface.

[0097] S2. Graphene preparation.

[0098] A single layer of graphene was grown on a copper foil substrate using CVD. The copper foil was placed in a CVD apparatus and heated to 900°C under argon protection. Hydrogen (at a flow rate of 60 sccm) and methane (at a flow rate of 12 sccm) were then introduced for 25 minutes, resulting in the growth of high-quality single-layer graphene on the copper foil surface.

[0099] After growth is complete, a layer of polymethyl methacrylate (PMMA) is spin-coated on the graphene surface to a thickness of approximately 90 nm as a transfer medium. The copper foil with the PMMA-graphene layer is then placed in a ferric chloride solution to etch away the copper foil, leaving a PMMA-graphene film suspended in the solution. The PMMA-graphene film is then rinsed multiple times with deionized water to remove any residual etching solution.

[0100] S3, corner-free graphene transfer.

[0101] According to the above steps S31-S35, the prepared PMMA-graphene film is precisely aligned with the pre-treated AlN substrate using a micromanipulation system to ensure that the relative rotation angle between the graphene and the substrate is 0±0.1°.

[0102] The PMMA-graphene film is then slowly transferred to the AlN substrate, and the graphene is tightly bonded to the substrate by heating (temperature controlled at 90°C).

[0103] The transferred sample was then placed in an acetone solution to dissolve and remove the PMMA, obtaining a corner-free graphene / AlN substrate.

[0104] S4. Remote epitaxial growth.

[0105] The AlN substrate, upon which the corner-free graphene had been transferred, was placed in an MOCVD apparatus. Growth was performed for 15 minutes at a growth temperature of 700°C, with a flow rate of 3500 sccm of ammonia, 25 sccm of TMGa, and a carrier gas mixture of 250 sccm of nitrogen and 35 sccm of hydrogen. Growth was then continued for 80 minutes at a growth temperature of 900°C, with a flow rate of 5500 sccm of ammonia, 35 sccm of TMGa, and a carrier gas mixture of 350 sccm of nitrogen and 45 sccm of hydrogen.

[0106] Finally, a 3 μm GaN film was obtained with a dislocation density of 8×10 7 cm -2 .

[0107] Results and Discussion: The relative rotation angle between graphene and substrate affects the interaction between them. To study the interface characteristics and further determine the structural model of graphene / AlN, the present invention performs first-principles calculations.

[0108] Specifically, according to the periodicity of the hexagonal lattice and the lattice matching relationship between graphene and AlN, such as Figure 6 As shown in the figure, SLG / AlN heterojunction structures with rotation angles of 0°, 10.9°, 13.9°, 19.1°, 23.4° and 30° between graphene and substrate were established (SLG is single-layer graphene), and their structures were optimized to calculate the equilibrium spacing of the heterojunction interface ( Figure 9 ), interface binding energy ( Figure 7 ) and the charge transfer capacity of graphene ( Figure 8 ), to explore the interaction between graphene and substrate at different rotation angles.

[0109] The equilibrium spacing and interfacial binding energy indicate that when the graphene and substrate are not rotated (angle = 0°), the distance is closest and the interaction is strongest. When the angle is 10.9°, the distance is largest and the interaction is weakest. Similarly, when there is no rotation between the two, the graphene receives more charge. Therefore, when there is no rotation between the AlN substrate and graphene, remote epitaxy is more favorable.

[0110] At the same time, based on the method of Example 1, by controlling the rotation angles of graphene and substrate to 0°, 10.9°, 13.9°, 19.1°, 23.4° and 30° respectively, and keeping other conditions unchanged, remote epitaxial growth of GaN film was finally obtained, and the dislocation densities of GaN film were measured and calculated to be 5×10 7 cm -2 , 8×10 8 cm -2 , 6×10 8 cm -2 , 1×10 8cm -2 , 5×10 8 cm -2 and 2×10 8 cm -2 Combining the above equilibrium spacing and interface binding energy data, it can be seen that the dislocation density of the final GaN film corresponds to the equilibrium spacing and interface binding energy of the interface in theoretical calculations.

[0111] When graphene is introduced into the remote epitaxy system, it is found that the relative angle between graphene and the substrate significantly affects the interaction between the two and the growth quality of the subsequent epitaxial layer. However, in the existing research, most of the effects of the relative angle between graphene and the substrate on remote epitaxy are not fully considered, resulting in problems such as large lattice mismatch, many defects, and uneven growth in the epitaxial layer growth, which makes it difficult to meet the demand for high-end device manufacturing for high-quality epitaxial layers. The present invention makes full use of the strongest interaction between graphene and the substrate when there is no angle by accurately controlling the relative angle between graphene and the substrate to 0±0.1°, thereby enhancing the bonding force between the two, improving the interface properties, and providing a more stable and more favorable growth substrate for remote epitaxial growth, which is conducive to reducing the lattice mismatch and defects between the epitaxial layer and the substrate. The angle-free graphene transfer is carried out using high-precision alignment equipment and mild transfer conditions, which ensures the integrity of the graphene and the good fit with the substrate, avoids the epitaxial growth problems caused by graphene damage or angle deviation, and improves the success rate of epitaxial growth and the quality of the epitaxial layer.

[0112] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

[0113] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

Claims

1. A remote epitaxial growth method for a nitride thin film, characterized in that: The steps include: Cover the graphene on the substrate, ensuring that the relative angle between the graphene and the substrate is 0±0.1°; A nitride film is remotely epitaxially grown on the graphene; the substrate has an m-plane in its crystal structure, and the graphene has an m-plane in its crystal structure. When the m-planes of the two are parallel to each other, the relative rotation angle between the graphene and the substrate is 0±0.1°; the m-plane is a crystal plane with a Miller index of (10-10) in the crystal structure.

2. The remote epitaxy method according to claim 1, wherein: The substrate is an AlN substrate or a GaN substrate; the graphene is a single-layer graphene or a multi-layer graphene. When it is a multi-layer graphene, the relative rotation angle between each layer of graphene and the substrate is 0±0.1°.

3. The remote epitaxy method according to claim 1, wherein: When covering the graphene on the substrate, the graphene is first grown on the metal substrate by chemical vapor deposition. After the growth is completed, a layer of PMMA is spin-coated on the surface of the graphene as a transfer medium. The metal substrate is then removed to obtain a PMMA-graphene film. The PMMA-graphene film is then transferred and covered on the substrate.

4. The remote epitaxy method according to claim 3, wherein: The PMMA-graphene film is transferred and covered onto the substrate, including the following steps: Using a micromanipulation system, the PMMA-graphene film is aligned with the substrate to ensure that the m-plane in the crystal structure of the substrate and the m-plane in the crystal structure of the graphene are parallel to each other, so that the relative rotation angle between the graphene and the substrate is 0±0.1°; then, the PMMA-graphene film is covered on the substrate, with one side of the graphene close to the substrate, and the graphene and the substrate are tightly adhered by heating; then, the transferred sample is placed in a solvent to dissolve and remove the PMMA, thereby obtaining a graphene / substrate material with a relative rotation angle of 0±0.1°.

5. The remote epitaxy method according to claim 4, wherein: The PMMA-graphene film is aligned with the substrate to ensure that the m-planes in the substrate's crystal structure and the m-planes in the graphene's crystal structure are parallel to each other. This is achieved by the following steps: Using the edge of the substrate's m-plane as a positioning reference, a crystal orientation reference mark is etched on the substrate; Before spin-coating PMMA on the graphene surface, the edge of the graphene on the metal substrate is identified, and the edge of the graphene m-plane is used as a positioning reference to etch directional marks on the graphene; Using a micromanipulation system, the crystal orientation reference mark on the substrate is aligned with the center of the directional mark on the graphene; Polarized reflection images of the substrate and graphene were collected separately; the crystallographic periodic signals of the two were extracted through Fourier transform, and the signal phase difference was confirmed to be ≤0.02°, completing the final alignment.

6. The remote epitaxy method according to claim 1, wherein: The material of the nitride film is gallium nitride, and the remote epitaxial growth of the nitride film includes the following steps: At a temperature of 800-1000°C, a nitrogen source with a flow rate of 2500-3500 sccm, a gallium source with a flow rate of 10-30 sccm, and a carrier gas are introduced for 10-30 minutes to grow a nucleation layer; Under the condition of a temperature of 800-1200° C., introducing a nitrogen source with a flow rate of 4000-6000 sccm, a gallium source with a flow rate of 20-40 sccm, and a carrier gas, and reacting for 70-110 minutes to grow a thin film layer on the nucleation layer to obtain the nitride thin film; The carrier gas includes nitrogen with a flow rate of 100 sccm-300 sccm and hydrogen with a flow rate of 20 sccm-40 sccm.

7. The remote epitaxy method according to any one of claims 1 to 6, characterized in that: The 3 μm thick nitride film prepared by the remote epitaxy method has a dislocation density of less than or equal to 9×10 7 cm -2 .

8. A nitride thin film, characterized in that: The nitride film is prepared by the method according to any one of claims 1 to 7.

9. A semiconductor device, characterized in that: comprising the nitride thin film as claimed in claim 8.

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