Nitride thin films, methods of remote epitaxy thereof, and semiconductor devices

Abstract

The application discloses a nitride film, a remote epitaxy method thereof and a semiconductor device, and relates to the technical field of semiconductor devices. The remote epitaxy method of the nitride film comprises the following steps: covering graphene on a substrate, and ensuring that the relative rotation angle between the graphene and the substrate is 0±0.1°; and growing a nitride film on the graphene through remote epitaxy; the substrate has an m face in a crystal structure, and the graphene has an m face in a crystal structure; when the m faces 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°; and the m face is a crystal face with a Miller index (10-10) in the crystal structure. The remote epitaxy method of the nitride film disclosed by the application controls the relative rotation angle between the graphene and the substrate to be 0±0.1°, enhances the interaction between the graphene and the substrate, and thus realizes high-quality remote epitaxy growth, thereby solving the problem of poor growth quality of a remote epitaxy layer in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of remote epitaxy and third-generation semiconductor materials, and particularly relates to a remote epitaxy method of a nitride film, a nitride film prepared by the method, and a semiconductor device comprising the nitride film. BACKGROUND

[0002] Gallium nitride (GaN) as a representative of the third-generation wide-bandgap semiconductor material has excellent physical properties such as a direct bandgap of 3.4 eV, a breakdown field strength of up to 3.3 MV / cm, and an electron saturation drift speed of 2.5 x 10 6 cm² / (V·s). These properties make it irreplaceable in the fields of high-efficiency optoelectronic devices and high-power electronic devices. For example, it has been industrialized and applied in the fields of blue / white light LEDs and laser diodes (LDs); in the field of power electronics, GaN-based HEMT devices are gradually replacing traditional silicon-based power devices due to their high frequency and low conduction loss advantages.

[0003] Remote epitaxy is an important technology for growing high-quality epitaxial layers on the surface of a substrate and has wide application prospects in the fields of semiconductor devices, optoelectronic devices, etc. In the process of remote epitaxy, the interface properties between the substrate and the epitaxial layer have a crucial influence on the quality and performance of the final epitaxial layer.

[0004] Graphene is widely used in various material systems due to its unique physical and chemical properties such as excellent electrical properties, high mechanical strength, and good chemical stability. However, in the existing research, the influence of the graphene and substrate corner on remote epitaxy has not been fully considered, resulting in problems such as large lattice mismatch, many defects, and uneven growth of the epitaxial layer, which makes it difficult to meet the demand for high-quality epitaxial layers in high-end device manufacturing.

[0005] The disclosure of the above background art content is only used to assist in understanding the inventive concept and technical solutions of the present application, and it does not necessarily belong to the prior art of the present patent application. In the absence of explicit evidence that the above content was disclosed before the filing date of the present patent application, the above background art should not be used to evaluate the novelty and inventiveness of the present application. SUMMARY

[0006] Therefore, the present application provides an improved remote epitaxy method of a nitride film, which effectively solves the existing technical problems and can prepare a nitride film with higher quality.

[0007] To achieve the above object, the technical solution adopted by the present application is as follows:

[0008] A remote epitaxy method of a nitride film, comprising the following steps:

[0009] covering graphene on the substrate, ensuring that the relative rotation angle between the graphene and the substrate is 0±0.1°;

[0010] remotely epitaxially growing a nitride film on the graphene;

[0011] the crystal structure of the substrate has an m-plane, the crystal structure of the graphene has an m-plane, and the m-planes of the two are parallel to each other, so that the relative rotation angle between the graphene and the substrate is 0±0.1°; the m-plane is a crystal plane with Miller indices (10-10) in the crystal structure.

[0012] Preferably, the crystal structures of the two are completely parallel, and the relative rotation angle is strictly 0°±θ (θ is a very small angle, θ≤0.1°), that is, the relative rotation angle between the graphene and the substrate is as close to 0° as possible.

[0013] According to some preferred embodiments of the present application, the substrate is an AlN substrate or a GaN substrate; the graphene is single-layer graphene or multi-layer graphene, and when it is multi-layer graphene, the relative rotation angle between each layer of graphene and the substrate is 0±0.1°. The multi-layer graphene is not more than two layers, that is, the graphene is preferably single-layer graphene or double-layer graphene, and more preferably single-layer graphene.

[0014] According to some preferred embodiments of the present application, when the graphene is covered on the substrate, the graphene is first grown on a metal substrate by chemical vapor deposition, a layer of polymethyl methacrylate (PMMA) is spin-coated on the surface of the graphene as a transfer medium after the growth is completed, the metal substrate is then removed to obtain a PMMA-graphene film, and the PMMA-graphene film is then transferred and covered on the substrate.

[0015] According to some preferred embodiments of the present application, the transfer and covering of the PMMA-graphene film on the substrate specifically includes the following steps:

[0016] The PMMA-graphene film and the substrate are aligned by using a micromanipulation system, the m-plane in the crystal structure of the substrate and the m-plane in the crystal structure of the graphene are ensured to be parallel to each other, so that the relative rotation angle between the graphene and the substrate is 0±0.1°; the PMMA-graphene film is then covered on the substrate with the graphene side close to the substrate, the graphene and the substrate are tightly attached by heating; and the transferred sample is then 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°.

[0017] 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, so that the expansion amounts of the two complement each other, the gap is reduced, and the graphene and the substrate are tightly attached.

[0018] In some embodiments of the present application, 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, which is achieved by the following steps:

[0019] The m-plane (10-10) edge of the substrate is used as a positioning reference to etch a crystal orientation reference mark on the substrate;

[0020] Before spin-coating PMMA on the graphene surface, the zigzag edge (m-plane) of the graphene on the metal substrate is identified, and the m-plane (10-10) edge of the graphene is used as a positioning reference to etch a directional mark on the graphene;

[0021] The crystal orientation reference mark on the substrate and the directional mark on the graphene are centered aligned by using a micromanipulation system;

[0022] Under the irradiation of a 532 nm laser, the polarized reflection images of the substrate and the graphene are collected respectively; the crystallographic periodic signals of the two are extracted by Fourier transform, and the phase difference of the signals is confirmed to be ≤0.02°, and the final alignment is completed.

[0023] According to some preferred embodiments of the present application, before the graphene is covered on the substrate, the substrate is pretreated: the substrate is sequentially placed in an acetone solution and an ethanol solution for ultrasonic cleaning, then washed with deionized water, and finally dried.

[0024] According to some preferred embodiments of the present application, the material of the nitride film is gallium nitride, and the remote epitaxial growth of the nitride film includes the following steps:

[0025] Under the condition that the temperature is 800-1000℃, the nitrogen source with a flow rate of 2500-3500sccm, the gallium source with a flow rate of 10-30sccm, and the carrier gas are introduced, and the reaction is carried out for 10-30min, a nucleation layer is grown;

[0026] Under the condition that the temperature is 800-1200℃, the nitrogen source with a flow rate of 4000-6000sccm, the gallium source with a flow rate of 20-40sccm, and the carrier gas are introduced, and the reaction is carried out for 70-110min, a film layer is grown on the nucleation layer to obtain the nitride film;

[0027] Among them, the carrier gas includes nitrogen with a flow rate of 100sccm-300sccm and hydrogen with a flow rate of 20sccm-40sccm.

[0028] According to some preferred embodiments of the present application, the nitride film with a thickness of 3um prepared by the remote epitaxial method has a dislocation density less than or equal to 9×10 7 cm -2 .

[0029] The application also provides a nitride film prepared by the method and a semiconductor device comprising the nitride film.

[0030] By using the technical scheme, the application has the following advantages compared with the prior art: the remote epitaxy method of the nitride film of the application enhances the interaction between graphene and the substrate by controlling the relative rotation angle between the graphene and the substrate to be 0±0.1°, thereby realizing high-quality remote epitaxy growth and solving the problem of poor growth quality of the remote epitaxy layer in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort.

[0032] Figure 1 A flowchart of the remote epitaxy method of the nitride film provided by the embodiment of the application;

[0033] Figure 2 A schematic diagram of the m-plane in the crystal structure of the substrate provided by the embodiment of the application;

[0034] Figure 3 A schematic diagram of the a-plane in the crystal structure of the substrate provided by the embodiment of the application;

[0035] Figure 4 A schematic diagram of the m-plane and the a-plane in the crystal structure of the graphene provided by the embodiment of the application;

[0036] Figure 5 A schematic diagram of the relative rotation angle between the graphene and the substrate being 0 in the embodiment of the application;

[0037] Figure 6 A schematic diagram of the graphene rotating different angles;

[0038] Figure 7 The interface binding energy of the graphene and the substrate at different rotation angles (the heterojunction top view is in the box);

[0039] Figure 8 The charge transfer amount of the graphene at different rotation angles;

[0040] Figure 9 The distance between the graphene and the substrate at different rotation angles (the heterojunction front view is in the box). DETAILED DESCRIPTION

[0041] In order to make the person skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should belong to the protection scope of the present application.

[0042] The present application provides a method for remote epitaxy growth of GaN epitaxial layer on graphene without corner with substrate, which optimizes the interaction between graphene and substrate, and further improves the quality of remote epitaxy growth. The method for remote epitaxy growth of nitride film in the present application comprises the following steps:

[0043] Covering graphene on the substrate to ensure that the relative corner between graphene and substrate is 0±0.1°;

[0044] Remote epitaxy growth of nitride film on graphene.

[0045] Preferably, the crystal structures of the two are completely parallel, and the relative corner is strictly 0°±θ (θ is a very small angle, θ≤0.1°), that is, the relative corner between graphene and substrate is 0° as much as possible.

[0046] The substrate is AlN substrate or GaN substrate; the graphene is single-layer graphene or multi-layer graphene, and when it is multi-layer graphene, the relative corner between each layer of graphene and the substrate is 0±0.1°. Preferably, the substrate is AlN substrate; the multi-layer graphene is not more than two layers, preferably single-layer graphene or double-layer graphene, and more preferably single-layer graphene.

[0047] As shown in Figures 2 to 5 , the crystal structure of the substrate has m face ( Figure 2 ) and a face ( Figure 3 ), and the crystal structure of the graphene has m face and a face ( Figure 4 ). When the relative corner between graphene and substrate is 0, that is, the m face in the crystal structure of the substrate and the m face in the crystal structure of the graphene are parallel to each other, and the a face in the crystal structure of the substrate and the a face in the crystal structure of the graphene are parallel to each other ( Figure 5 ). Figure 5 This expression is an ideal state, and in actual situation, the ring crystal structure of graphene does not necessarily locate in the ring crystal structure of the substrate, but will be offset, as long as the m face in the crystal structure of the substrate and the m face in the crystal structure of the graphene are parallel to each other. The m face in the present application is the crystal face with Miller index (10-10) in the crystal structure, and the a face is the crystal face with Miller index (11-20) in the crystal structure.

[0048] AsFigure 1 The remote epitaxy method of the nitride film of the present application specifically comprises the following steps:

[0049] S1, substrate pretreatment.

[0050] Select a suitable substrate material, such as aluminum nitride (AlN) substrate.

[0051] The substrate is subjected to cleaning treatment to remove impurities and oxides on the surface. The specific cleaning process can use organic solvents (such as acetone, ethanol) for ultrasonic cleaning, then rinse with deionized water, and finally remove the surface moisture through drying treatment to obtain a clean substrate surface, providing a good foundation for subsequent graphene transfer and epitaxial growth.

[0052] S2, graphene preparation.

[0053] High-quality single-layer graphene is grown on a metal substrate (such as copper foil) using chemical vapor deposition (CVD) method. Control various parameters during CVD growth, such as reaction temperature, gas flow, growth time, etc., to obtain large-area, defect-free graphene film.

[0054] After growth, the graphene is transferred from the metal substrate by wet transfer process. A suitable transfer medium (such as polymethyl methacrylate, PMMA) is used during the transfer process to avoid damage to the graphene.

[0055] Specifically, when covering the graphene on the substrate, first grow single-layer graphene on the metal substrate using chemical vapor deposition method. After growth, spin a layer of polymethyl methacrylate on the surface of the graphene as a transfer medium, then remove the metal substrate to obtain a PMMA-graphene film, and then transfer and cover the PMMA-graphene film on the substrate.

[0056] S3, corner-free graphene transfer.

[0057] Use high-precision alignment equipment, such as a micro-operation system (optical microscope combined with a micro-operation platform), to accurately align the prepared graphene with the substrate, ensuring that the relative rotation angle between the graphene and the substrate is 0±0.1°.

[0058] During the transfer process, use mild transfer conditions, such as controlling the transfer temperature, to avoid wrinkles, damage or unnecessary stress between the graphene and the substrate due to high temperature, ensuring that the graphene and the substrate are tightly bonded without corner deviation.

[0059] Preferably, the steps of transferring and covering the PMMA-graphene film on the substrate specifically include the following steps:

[0060] The PMMA-graphene film is aligned with the substrate by using a micro-manipulation system, 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 the substrate are tightly attached by heating; then the transferred sample is placed in a solvent to dissolve and remove the PMMA, to obtain a graphene / substrate material with a relative rotation angle of 0±0.1°.

[0061] The solvent for dissolving and removing the PMMA is preferably acetone, and the surface tension of the acetone solvent is much smaller than the graphene-substrate adsorption energy; and the acetone dissolution of the PMMA almost does not generate torque, which can better ensure that the graphene does not separate from the substrate and does not change the rotation angle.

[0062] The heating temperature is preferably 90-110°C, and the time is 30-60 min. During heating, the substrate and the graphene undergo differential thermal expansion, so that the expansion amounts of the two complement each other, the gap is reduced, and the graphene and the substrate are tightly attached.

[0063] In some embodiments, 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, by the following steps:

[0064] The m-plane (10-10) edge of the substrate is taken as a positioning reference, and a crystal orientation reference mark is etched on the substrate;

[0065] Before spin-coating PMMA on the graphene surface, the sawtooth-shaped edge (m-plane) of the graphene on the metal substrate is identified, and the m-plane (10-10) edge of the graphene is taken as a positioning reference, and a directional mark is etched on the graphene;

[0066] The crystal orientation reference mark on the substrate and the directional mark on the graphene are aligned by using a micro-manipulation system;

[0067] Under the irradiation of a 532 nm laser, polarized reflection images of the substrate and the graphene are collected respectively; the crystallographic periodic signals of the two are extracted by Fourier transform, and it is confirmed that the signal phase difference is ≤0.02°, and the final alignment is completed.

[0068] S4, remote epitaxial growth.

[0069] The substrate on which the angle-free graphene transfer is completed is placed in an epitaxial growth device (such as MOCVD), and remote epitaxial growth is performed under suitable growth conditions. According to the characteristics of the target epitaxial material, the temperature, gas flow, growth time and other parameters in the growth process are accurately controlled, so that the epitaxial material grows on the system composed of the angle-free graphene and the substrate.

[0070] Preferably, the material of the nitride thin film is gallium nitride, and the remote epitaxy growth of the nitride thin film comprises the following steps:

[0071] Under the condition of a temperature of 800-1000℃, a nitrogen source with a flow rate of 2500-3500sccm, a gallium source with a flow rate of 10-30sccm, and a carrier gas are introduced, and the reaction is carried out for 10-30min to grow a nucleation layer;

[0072] Under the condition of a temperature of 800-1200℃, a nitrogen source with a flow rate of 4000-6000sccm, a gallium source with a flow rate of 20-40sccm, and a carrier gas are introduced, and the reaction is carried out for 70-110min to grow a thin film layer on the nucleation layer, thereby obtaining a nitride thin film;

[0073] The carrier gas comprises nitrogen with a flow rate of 100sccm-300sccm and hydrogen with a flow rate of 20sccm-40sccm.

[0074] The nitride thin film prepared by the above remote epitaxy method has a thickness of 3um, and the dislocation density of the thin film is less than or equal to 9×10 7 cm -2 . Meanwhile, the nitride thin film prepared by the above method can be applied to a semiconductor device.

[0075] In some embodiments of the present application, the remote epitaxy method of the nitride thin film specifically comprises the following steps:

[0076] S1, substrate pretreatment.

[0077] An AlN substrate is selected, the substrate is first cleaned in an acetone solution for 10-20min by ultrasonic cleaning to remove surface particulate impurities, then cleaned in an ethanol solution for 10-20min by ultrasonic cleaning to further clean the surface, then the substrate is washed with deionized water for multiple times to remove residual organic solvents, and finally the substrate is placed in a drying box and dried at 70-90℃ for 20-40min to obtain a clean substrate surface.

[0078] S2, graphene preparation.

[0079] Single-layer graphene is grown on a copper foil substrate by a CVD method. The copper foil is placed in a CVD device, heated to 900-1100℃ under argon protection, then hydrogen (with a flow rate of 40-60sccm) and methane (with a flow rate of 8-12sccm) are introduced, and the growth time is 25-35min, thereby growing high-quality single-layer graphene on the surface of the copper foil.

[0080] After the growth is completed, a layer of polymethyl methacrylate (PMMA) is spin-coated on the graphene surface as a transfer medium, with a thickness of 90-110 nm. Then the copper foil with PMMA-graphene is placed in a ferric chloride solution, and the copper foil is removed by etching to obtain a PMMA-graphene film suspended in the solution. The PMMA-graphene film is washed with deionized water multiple times to remove the residual etching solution.

[0081] S3, corner-free graphene transfer.

[0082] Using a micromanipulation system (optical microscope combined with a micromanipulation platform), the PMMA-graphene film prepared above is accurately aligned to the pretreated AlN substrate to ensure that the relative angle between the graphene and the substrate is 0±0.1°.

[0083] Then the PMMA-graphene film is slowly transferred to the AlN substrate with the graphene side close to the substrate, and the graphene is tightly attached to the substrate by heating (the temperature is controlled at 90-110°C).

[0084] Next, the transferred sample is placed in an acetone solution to dissolve and remove the PMMA, obtaining a corner-free graphene / AlN substrate.

[0085] Step S3, corner-free graphene transfer, specifically includes the following steps:

[0086] S31, substrate crystal orientation marking.

[0087] On the surface of the AlN substrate pretreated in step S1, a crystal orientation reference mark is made on the substrate using a focused ion beam (FIB).

[0088] Specifically, the m face (10-10) edge 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. 1B, wherein one of the cross-shaped marks is parallel to the m face of the substrate. Figure 5

[0089] S32, graphene crystal orientation marking.

[0090] Before the PMMA is spin-coated on the graphene surface in step S2, a directional mark is made on the graphene m face edge using electron beam lithography (EBL).

[0091] Specifically, the sawtooth-shaped edge (m face) of the 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 of the mark to the sawtooth-shaped edge is ≤0.03°, as shown in FIG. 2B, i.e., the straight line mark is parallel to the graphene m face. Figure 5

[0092] ​​S33, step-by-step alignment operation.

[0093] 1) Coarse alignment (±1° range).

[0094] By identifying the cross mark of the substrate and the straight mark of graphene, adjust the platform X-Y axis translation in the micro-manipulation system to make the center deviation of both ≤50μm, and rotate the platform to make the included angle of the mark lines ≤1°.

[0095] 2) Fine alignment (±0.1° range).

[0096] Switch the micro-manipulation system to 1000x magnification. Take the substrate m-plane mark line (crystal direction reference mark) as the reference, and adjust by step (step size 0.005°) through the piezoelectric rotation stage of the micro-manipulation system, and monitor the included angle change of the graphene mark line (directionality mark) and the substrate mark line (crystal direction reference mark) in real time. When the included angle ≤0.05°, lock the rotation axis of the micro-manipulation system.

[0097] S34, crystallographic direction verification.

[0098] Under the irradiation of 532nm laser, use the polarized microscope module of the micro-manipulation system to collect the polarization reflection images of the substrate and graphene respectively. Extract the crystallographic periodic signals of both (such as the m-plane period of AlN 0.311nm and the sawtooth edge period of graphene 0.246nm) through Fourier transform, and confirm that the phase difference of the signals ≤0.02°, to complete the final alignment.

[0099] S35, transfer.

[0100] After alignment, slowly transfer the PMMA-graphene film to the AlN substrate.

[0101] S4, remote epitaxial growth.

[0102] Put the AlN substrate with completed corner-free graphene transfer into the MOCVD equipment.

[0103] At a growth temperature of 700-900℃, ammonia flow rate of 2500-3500sccm, TMGa flow rate of 15-25sccm, carrier gas of mixed gas of nitrogen 150-250sccm and hydrogen 25-35sccm, grow for 15-25 minutes. At a growth temperature of 900-1100℃, ammonia flow rate of 4500-5500sccm, TMGa flow rate of 25-35sccm, carrier gas of mixed gas of nitrogen 250-350sccm and hydrogen 35-45sccm, grow for 80-100 minutes.

[0104] Finally obtain a 3μm GaN film, and the dislocation density of the film is less than or equal to 9×10 7 cm-2 .

[0105] Embodiment 1: In this embodiment, the remote epitaxy method of nitride thin film specifically comprises the following steps:

[0106] S1, substrate pretreatment.

[0107] Selecting an AlN substrate, first, the substrate is placed in an acetone solution for ultrasonic cleaning for 15 minutes to remove surface particulate impurities; then placed in an ethanol solution for ultrasonic cleaning for 15 minutes to further clean the surface; then the substrate is rinsed with deionized water multiple times to remove residual organic solvents; finally, the substrate is placed in a drying oven at 80°C for 30 minutes to obtain a clean substrate surface.

[0108] S2, graphene preparation.

[0109] Single-layer graphene is grown on a copper foil substrate using the CVD method. The copper foil is placed in a CVD device, heated to 1000°C under argon protection, then hydrogen (flow rate of 50 sccm) and methane (flow rate of 10 sccm) are introduced, and the growth time is 30 minutes, growing high-quality single-layer graphene on the surface of the copper foil.

[0110] After growth is complete, a layer of polymethyl methacrylate (PMMA) is spin-coated on the surface of the graphene as a transfer medium, with a thickness of about 100 nm. Then the copper foil with PMMA-graphene is placed in a ferric chloride solution, and the copper foil is etched to obtain a PMMA-graphene film suspended in the solution. The PMMA-graphene film is rinsed with deionized water multiple times to remove residual etching solution.

[0111] S3, corner-free graphene transfer.

[0112] According to the above steps S31-S35, using a micromanipulation system, the above prepared PMMA-graphene film is accurately aligned with the pretreated AlN substrate to ensure that the relative angle between the graphene and the substrate is 0±0.1°.

[0113] Then the PMMA-graphene film is slowly transferred to the AlN substrate, with the graphene side close to the substrate, and the graphene is tightly attached to the substrate by heating (temperature controlled at 100°C).

[0114] Next, the transferred sample is placed in an acetone solution to dissolve and remove the PMMA, obtaining a corner-free graphene / AlN substrate.

[0115] S4, remote epitaxy growth.

[0116] The AlN substrate on which the corner-free graphene is transferred is placed in a MOCVD device. At a growth temperature of 800℃, ammonia flow of 3000sccm, TMGa flow of 20sccm, and mixed gas of nitrogen of 200sccm and hydrogen of 30sccm as carrier gas, the growth is performed for 20 minutes. At a growth temperature of 1000℃, ammonia flow of 5000sccm, TMGa flow of 30sccm, and mixed gas of nitrogen of 300sccm and hydrogen of 40sccm as carrier gas, the growth is performed for 90 minutes.

[0117] Finally, a 3μm GaN film is obtained, and the dislocation density of the film is 5×10 7 cm -2 .

[0118] In this embodiment, the remote epitaxy method of the nitride film specifically includes the following steps:

[0119] S1, substrate pretreatment.

[0120] An AlN substrate is selected. First, the substrate is placed in an acetone solution for ultrasonic cleaning for 10 minutes to remove surface particulate impurities. Then, the substrate is placed in an ethanol solution for ultrasonic cleaning for 20 minutes to further clean the surface. Next, the substrate is rinsed with deionized water multiple times to remove residual organic solvents. Finally, the substrate is placed in a drying box and dried at 90℃ for 20 minutes to obtain a clean substrate surface.

[0121] S2, graphene preparation.

[0122] Single-layer graphene is grown on a copper foil substrate by CVD method. The copper foil is placed in a CVD device, heated to 1100℃ under argon protection, and then hydrogen (flow rate of 40sccm) and methane (flow rate of 8sccm) are introduced. The growth time is 35 minutes, and high-quality single-layer graphene is grown on the surface of the copper foil.

[0123] After the growth is completed, a layer of polymethyl methacrylate (PMMA) is spin-coated on the surface of the graphene as a transfer medium, with a thickness of about 110nm. Then, the copper foil with PMMA-graphene is placed in a ferric chloride solution, and the copper foil is etched to obtain a PMMA-graphene film suspended in the solution. The PMMA-graphene film is rinsed with deionized water multiple times to remove residual etching solution.

[0124] S3, corner-free graphene transfer.

[0125] According to the above steps S31-S35, the prepared PMMA-graphene film is accurately aligned with the pretreated AlN substrate by using a micro-manipulation system, and the relative angle between the graphene and the substrate is ensured to be 0±0.1°.

[0126] Then the PMMA-graphene film is slowly transferred onto the AlN substrate with the graphene side close to the substrate, and the graphene is tightly attached to the substrate by heating (temperature controlled at 110℃).

[0127] Then the transferred sample is put into an acetone solution to dissolve and remove the PMMA, obtaining a graphene / AlN substrate without corner.

[0128] S4, remote epitaxial growth.

[0129] The AlN substrate with the transferred graphene without corner is put into a MOCVD device. At a growth temperature of 900℃, ammonia flow of 2500sccm, TMGa flow of 15sccm, and mixed gas of nitrogen 150sccm and hydrogen 25sccm as carrier gas, the growth is performed for 25 minutes. At a growth temperature of 1100℃, ammonia flow of 4500sccm, TMGa flow of 25sccm, and mixed gas of nitrogen 250sccm and hydrogen 35sccm as carrier gas, the growth is performed for 100 minutes.

[0130] Finally, a 3μm GaN film is obtained, and the dislocation density of the film is 9×10 7 cm -2 .

[0131] Example 3: In this example, the remote epitaxial method for growing a nitride film includes the following steps:

[0132] S1, substrate pretreatment.

[0133] An AlN substrate is selected. First, the substrate is put into an acetone solution for ultrasonic cleaning for 20 minutes to remove surface particulate impurities. Then, the substrate is put into an ethanol solution for ultrasonic cleaning for 11 minutes to further clean the surface. Then, the substrate is rinsed with deionized water multiple times to remove residual organic solvents. Finally, the substrate is put into a drying box and dried at 70℃ for 40 minutes to obtain a clean substrate surface.

[0134] S2, graphene preparation.

[0135] Single-layer graphene is grown on a copper foil substrate by CVD method. The copper foil is put into a CVD device, heated to 900℃ under argon protection, then hydrogen (flow rate of 60sccm) and methane (flow rate of 12sccm) are introduced, and the growth time is 25 minutes. High-quality single-layer graphene is grown on the surface of the copper foil.

[0136] After the growth is completed, a layer of polymethyl methacrylate (PMMA) is spin-coated on the graphene surface as a transfer medium, and the thickness is about 90 nm. Then the copper foil with PMMA-graphene is placed in a ferric chloride solution, and the copper foil is removed by etching to obtain a PMMA-graphene film suspended in the solution. The PMMA-graphene film is washed with deionized water for several times to remove the residual etching solution.

[0137] S3, corner-free graphene transfer.

[0138] According to the above steps S31-S35, the above prepared PMMA-graphene film is accurately aligned to the pretreated AlN substrate by using a micro-manipulation system, so as to ensure that the relative corner angle between the graphene and the substrate is 0±0.1°.

[0139] Then the PMMA-graphene film is slowly transferred to the AlN substrate, and the graphene is tightly attached to the substrate by heating (the temperature is controlled at 90°C).

[0140] Then the transferred sample is placed in an acetone solution to dissolve and remove the PMMA, and a corner-free graphene / AlN substrate is obtained.

[0141] S4, remote epitaxial growth.

[0142] The AlN substrate on which the corner-free graphene is transferred is placed in a MOCVD device. At a growth temperature of 700°C, an ammonia flow of 3500 sccm, a TMGa flow of 25 sccm, and a mixed gas of nitrogen 250 sccm and hydrogen 35 sccm as a carrier gas, the growth is performed for 15 minutes. At a growth temperature of 900°C, an ammonia flow of 5500 sccm, a TMGa flow of 35 sccm, and a mixed gas of nitrogen 350 sccm and hydrogen 45 sccm as a carrier gas, the growth is performed for 80 minutes.

[0143] Finally, a 3 μm thick GaN film is obtained, and the dislocation density of the film is 8×10 7 cm -2 .

[0144] Results and discussion: The relative corner angle between the graphene and the substrate affects the interaction between them. In order to study the interface characteristics and further determine the structure model of graphene / AlN, the present application performs first-principle calculation.

[0145] Specifically, according to the periodicity of the hexagonal lattice and the lattice matching relationship between the graphene and the AlN, as shown in FIG. 1, SLG / AlN heterojunction structures (SLG is single-layer graphene) with corner angles of 0°, 10.9°, 13.9°, 19.1°, 23.4° and 30° between the graphene and the substrate are established, and the structures are optimized to calculate the equilibrium spacing of the heterojunction interface (d0) and the interface stress (σ0) of the SLG / AlN heterojunction structures. Figure 6 ​Figure 9 ), interface binding energy (E Figure 7 ) and charge transfer amount (Q Figure 8 ) of graphene, and explore the interaction between graphene and substrate under different rotation angles.

[0146] From the equilibrium distance and interface binding energy, it can be seen that when graphene and substrate have no rotation angle (0°), the distance is the closest and the force is the strongest, and when the rotation angle is 10.9°, the distance is the largest and the force is the weakest. Similarly, when there is no rotation angle between the two, graphene obtains more charges. Therefore, when the AlN substrate has no rotation angle with graphene, it is more conducive to remote epitaxy.

[0147] Meanwhile, based on the method of embodiment 1, by controlling the rotation angle between graphene and substrate to be 0°, 10.9°, 13.9°, 19.1°, 23.4° and 30° respectively, and keeping other conditions unchanged, the remote epitaxial growth of GaN thin film is carried out, and finally the GaN thin film is obtained. The dislocation density is measured and calculated to be 5×10 7 cm -2 , 8×10 8 cm -2 , 6×10 8 cm -2 , 1×10 8 cm -2 , 5×10 8 cm -2 and 2×10 8 cm -2 . Combined with the above equilibrium distance and interface binding energy data, it can be seen that the dislocation density of the finally obtained GaN thin film corresponds to the equilibrium distance and interface binding energy of the interface in the theoretical calculation.

[0148] When graphene is introduced into the remote epitaxy system, it is found that the relative rotation angle between graphene and substrate will significantly affect the interaction between the two and the growth quality of the subsequent epitaxial layer. However, in the existing research, the influence of the relative rotation angle between graphene and substrate on remote epitaxy is not fully considered, resulting in problems such as large lattice mismatch, many defects, uneven growth, etc. in epitaxial layer growth, which is difficult to meet the demand for high-quality epitaxial layer for high-end device manufacturing. The present application precisely controls the relative rotation angle between graphene and substrate to be 0±0.1°, fully utilizes the characteristic that the interaction between graphene and substrate is the strongest when there is no rotation angle, enhances the binding force between the two, improves the interface properties, and provides 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 non-rotation angle graphene transfer is carried out by using high-precision alignment equipment and mild transfer conditions, which ensures the integrity of graphene and good fitting with the substrate, avoids the epitaxial growth problems caused by graphene damage or rotation angle deviation, and improves the success rate of epitaxial growth and the quality of epitaxial layer.

[0149] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application should be covered within the protection scope of the present application.

[0150] The endpoints of the ranges and any values described herein are not limited to the precise values recited as exactly that endpoint point, but rather to also be understood as including values approximately around that value as would be appreciated by persons skilled in the art pertaining to the ranges and values. For values whose endpoints define the range, combinations of the maximum and minimum include every number and value therebetween. For values whose endpoints do not both define the range, every number and value there-between, and also every number and value outside of the endpoint range, are considered available.

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 less than or equal to 9×10 7 cm -2 .

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