Method for processing substrate to be epitaxially grown, epitaxial growth method and epitaxial structure

Abstract

The invention relates to a processing method of a substrate to be epitaxially grown, an epitaxial growth method and an epitaxial structure, and the processing method of the substrate to be epitaxially grown comprises the following steps: S100, providing an original substrate, grinding the back of the substrate to enable the stress in the original substrate to be uniformly distributed, and performing surface repair to obtain a first processed substrate; s200, providing single-layer graphene, and transferring the single-layer graphene to the surface of the first treated substrate to obtain a second treated substrate; and S300, providing a liquid containing an epitaxial layer nucleation promoting nanowire, uniformly smearing the liquid on the second treatment substrate, and drying to obtain a substrate to be subjected to epitaxial growth.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technology, and in particular to a substrate processing method to be epitaxially grown, an epitaxial growth method and an epitaxial structure. Background Art

[0002] Different from traditional LCD and OLED, Micro-LED based on III-V compound semiconductors has ultra-high brightness (~10 7 cd / m 2 OLED is 1500cd / m 2 ), nanosecond response time (10 times lower than OLED and LCD 4 and 10 7 It is often considered as the ultimate display due to its unique properties such as low brightness (less than times), extremely low power consumption (1% of LCD and 40% of OLED), ultra-long life (more than ten years, 4 years for OLED and 8 years for LCD) and high color reproduction ability (75% of LCD and 100% of OLED). In recent years, it has received widespread attention from academia and industry at home and abroad.

[0003] With the rapid development of Micro-LED, it is widely used in fields ranging from ultra-large displays to ultra-high-resolution VR glasses and head-mounted displays. Micro-LED chip size is usually small, less than 50μm. Therefore, under the premise of ensuring its yield, the wavelength uniformity of Micro-LED epitaxial wafers is required to be within ±1nm. Therefore, in order to ensure the chip yield and reduce the manufacturing cost of Micro-LED, there are extremely high requirements for the quality and uniformity of epitaxial materials.

[0004] At present, GaN-based LEDs generally use sapphire as epitaxial substrate. However, due to the heterogeneous epitaxy between gallium nitride and sapphire, the lattice mismatch and thermal mismatch will generate internal stress during the epitaxy process, forming a large number of defects and dislocations, causing the wavelength of the chip to shift and leakage. In addition, the presence of stress will also cause the epitaxial wafer to warp and cause the quantum Stark effect, reducing the luminous efficiency of the device and seriously affecting the device performance, which is unacceptable for Micro LEDs. Studies have shown that effective regulation of stress during the epitaxy process will greatly improve the quality of the epitaxial material and thus improve the performance of the device.

[0005] With the continuous development and breakthrough of substrate and epitaxial technology, the stress in the active area can be effectively released by designing InGaN / GaN superlattice structure; the stress in GaN growth process can be effectively regulated by adopting AlN buffer layer technology; the stress in epitaxial process can be regulated by etching patterns on the front or back of the substrate. Although these can effectively improve stress by adding other epitaxial structures and changing the morphology of the substrate, they cannot fundamentally reduce the generation of stress, increase the difficulty of the process, and are not conducive to the stability and repeatability of production. Summary of the invention

[0006] In view of the above analysis, embodiments of the present invention aim to provide a substrate processing method for epitaxial growth, an epitaxial growth method and an epitaxial structure, so as to solve at least one of the above problems.

[0007] In one aspect, the present invention provides a method for processing a substrate to be epitaxially grown, comprising the following steps:

[0008] S100: providing an original substrate, grinding the back of the substrate to evenly distribute stress in the original substrate, and performing surface repair to obtain a first processed substrate;

[0009] S200: providing a single-layer graphene, and transferring the single-layer graphene to a surface of a first processed substrate to obtain a second processed substrate;

[0010] S300: providing a liquid containing epitaxial layer-promoting nucleation nanowires, and evenly applying the liquid on a second processing substrate, and drying to obtain a substrate for epitaxial growth.

[0011] Further, the original substrate is classified by its related parameters, and then the back of the original substrate is ground appropriately by chemical mechanical polishing technology to prepare for uniform stress distribution in the substrate;

[0012] The related parameters include but are not limited to one of BOW, Warp, TTV, and LTV.

[0013] Furthermore, the chemical mechanical polishing technology adopts a polishing speed of 10 to 100 r / min and a pressure range of 10 to 50 Kpa;

[0014] The grinding time is adapted to the classification of the original substrate.

[0015] Furthermore, the original substrate is divided into five grades according to the BOW value range of -10 to 0, with 2 as the segment interval;

[0016] The polishing speed adopted by the chemical mechanical polishing technology is 30r / min and the pressure is 20Kpa. When the BOW value of the original substrate is between -10 and -8, the polishing time is controlled at 30s; when the BOW value of the original substrate is between -8 and -6, the polishing time is controlled at 25s; when the BOW value of the original substrate is between -6 and -4, the polishing time is controlled at 20s; when the BOW value of the original substrate is between -4 and -2, the polishing time is controlled at 15s; when the BOW value of the original substrate is between -2 and 0, the polishing time is controlled at 10s.

[0017] Furthermore, the surface repair is to immerse the ground substrate in an acidic liquid.

[0018] Furthermore, a single layer of graphene is grown on a Cu substrate by using a CVD method, and then the single layer of graphene on the Cu substrate is transferred to the surface of the first processing substrate by using a chemical etching and wet transfer method.

[0019] Furthermore, the nanowire has a width of 3 to 5 μm and a length of less than 50 μm.

[0020] In another aspect, the present invention provides an epitaxial growth method, comprising the following steps:

[0021] Z100: providing a substrate to be epitaxially grown obtained by the above substrate processing method;

[0022] Z200: placing the substrate to be epitaxially grown into an epitaxial furnace for epitaxial growth and depositing the epitaxial layer;

[0023] Z300: Deposition of functional layers on the epitaxial layer.

[0024] Furthermore, the epitaxial layer includes a stacked u-GaN layer, an n-GaN layer, an MQW layer, a p-AlGaN layer and a p-GaN layer.

[0025] In a final aspect, the present invention provides an epitaxial structure, comprising:

[0026] base substrate;

[0027] Single graphene layer;

[0028] Nanowire layer;

[0029] Epitaxial layer;

[0030] Functional layer.

[0031] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0032] (1) The substrate processing method of the present invention can make the epitaxial layer and the substrate more compatible, can effectively regulate the stress and polarization electric field during the epitaxial process, and reduce the stress during the epitaxial process;

[0033] (2) The present invention utilizes the unique properties of two-dimensional materials to effectively reduce dislocations generated during the epitaxial growth process, and can achieve electrochemical and mechanical stripping, thereby avoiding laser stripping that damages chip quality;

[0034] (3) The present invention uses epitaxial layer to promote nucleation of nanowires as nucleation points, thereby reducing the epitaxial temperature and protecting the surface two-dimensional material; further regulating the stress during the epitaxial process and improving the crystal quality.

[0035] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0037] Figure 1 It is a schematic diagram of a process of a substrate processing method in a specific implementation manner;

[0038] Figure 2 It is a schematic flow chart of the epitaxial growth method in a specific implementation manner;

[0039] Figure 3 is a schematic diagram of an epitaxial structure in a specific implementation manner;

[0040] Figure 4 It is a comparison diagram of XRD data of epitaxial GaN of the example group substrate and the control group substrate in the specific implementation manner;

[0041] Figure 5 This is a SEM image of a U-GaN epitaxial wafer deposited after substrate processing in an example group in a specific implementation manner;

[0042] Figure 6 It is a PL test diagram of an example group epitaxial structure high-performance LED in a specific implementation manner.

[0043] Reference numerals:

[0044] 10 - original substrate; 20 - first processed substrate; 30 - single-layer graphene layer; 31 - single-layer graphene; 40 - nanowire layer; 41 - epitaxial layer promoting nucleation of nanowires; 50 - epitaxial layer; 60 - functional layer. DETAILED DESCRIPTION

[0045] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0046] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the term "connected" should be understood in a broad sense, for example, it can be a fixed connection, or a detachable connection, or an integral connection, which can be a mechanical connection, or an electrical connection, which can be a direct connection, or can be indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] The terms "top", "bottom", "above", "lower", and "on" used throughout the description are relative to the relative positions of components of a device, such as the relative positions of the top and bottom substrates within a device. It is understood that devices are multifunctional regardless of their orientation in space.

[0048] The common working surface of the present invention can be a plane or a curved surface, can be inclined, or can be horizontal. For the convenience of description, the embodiment of the present invention is placed on a horizontal plane and used on the horizontal plane, and "high and low" and "up and down" are defined in this way.

[0049] A specific embodiment of the present invention discloses a method for processing a substrate to be epitaxially grown, such as Figure 1 As shown, the following steps are included:

[0050] S100: providing an original substrate 10, grinding the back of the substrate to make the stress in the original substrate 10 uniformly distributed, and performing surface repair to obtain a first processed substrate 20;

[0051] S200: providing a single-layer graphene 31, and transferring the single-layer graphene 31 to the surface of the first processing substrate 20 to obtain a second processing substrate; that is, laying the single-layer graphene 31 on the first processing substrate 20 to form a single-layer graphene layer 30;

[0052] S300: providing a liquid containing epitaxial layer-promoting nucleation nanowires, and evenly applying the liquid on a second processing substrate, and drying to obtain a substrate for epitaxial growth; that is, evenly distributing epitaxial layer-promoting nucleation nanowires 41 on the second processing substrate to form a nanowire layer 40.

[0053] In step S100, the substrate is the cornerstone of epitaxial growth. The original substrate 10 is preferably an m-plane sapphire substrate, which is a non-polar surface. The gallium nitride epitaxially grown thereon can effectively reduce its internal polarization electric field. For the LED structure, it can effectively suppress its quantum Stark effect and improve the light conversion efficiency of the LED.

[0054] The original substrate is classified by its BOW (bow), Warp (warp), TTV (Total Thickness Variation, global thickness difference), LTV (Local Thickness Variation, local thickness difference) and other values, that is, it is classified by the relevant parameters of the original substrate, and then the back of the original substrate is ground appropriately by chemical mechanical polishing technology, so that the stress in the substrate can be evenly distributed, so as to better adapt to the later epitaxial layer growth. According to the classification of the original substrate, the grinding amount during grinding is controlled to cause the amount and degree of molecular bond breaking, giving the substrate a reverse stress, thereby combining the internal stress of the substrate itself, and finally causing the warpage of the wafer to change and the wafer flatness to increase. Therefore, accurately controlling the grinding amount on the back of the substrate can accurately control the stress of the substrate. If the grinding amount is too large, the substrate will show reverse stress, and the substrate morphology may change from concave to convex. If the grinding amount is too small, it cannot balance the internal stress of the substrate.

[0055] The chemical mechanical polishing technology uses a polishing speed of 10 to 100 r / min, preferably 30 r / min; a pressure range of 10 to 50 Kpa, preferably 20 Kpa. The abrasives used in the chemical mechanical polishing technology include but are not limited to colloidal silica, diamond, etc., and the abrasives are preferably colloidal silica. Colloidal silica and sapphire Al2O3 will undergo a solid phase reaction during the polishing process to generate softer and more adhesive aluminum silicate with colloidal SiO2; further, colloidal SiO2 removes the soft products on the surface mechanically at the atomic level. An atomic-level ultra-smooth surface can be formed.

[0056] Exemplarily, the m-plane sapphire substrate is classified according to the BOW value. Taking a 4-inch sapphire substrate as an example, its BOW value range is -10 to 0, with 2 as the segment interval, and the interval is not less than 5. The polishing speed used in the chemical mechanical polishing technology is 30r / min, the pressure is 20Kpa, and the grinding rate is 4μm / min. When the BOW value of the original substrate is divided into -10 to -8, the grinding time is controlled at 30s; when the BOW value of the original substrate is divided into -8 to -6, the grinding time is controlled at 25s; when the BOW value of the original substrate is divided into -6 to -4, the grinding time is controlled at 20s; when the BOW value of the original substrate is divided into -4 to -2, the grinding time is controlled at 15s; when the BOW value of the original substrate is divided into -2 to 0, the grinding time is controlled at 10s.

[0057] Preferably, the surface repair is to immerse the ground substrate in an acidic liquid to repair surface defects. Specifically, the acidic liquid is a mixture of sulfuric acid and phosphoric acid, and the volume ratio of sulfuric acid to phosphoric acid is 3:1. If the ground substrate is immersed in the mixture of sulfuric acid and phosphoric acid at room temperature, the time is preferably 10 to 60 seconds; if the ground substrate is immersed in the mixture of sulfuric acid and phosphoric acid at 50 to 300°C, the time is preferably 5 to 30 seconds. Such treatment can repair the defects generated by the substrate during grinding and reduce the stress during the epitaxial process. Preferably, the mass fraction of sulfuric acid is 98%, and the mass fraction of phosphoric acid is 85%.

[0058] The substrate soaked in the acid solution is rinsed with deionized water to remove the residual acid on the surface, and then dried with a spin dryer to obtain a first processed substrate. Preferably, the deionized water is ultrasonically rinsed for more than 30 minutes.

[0059] In the step S200, a single layer of graphene is grown on a Cu substrate by using a CVD (Chemical Vapor Deposition) method, and then the single layer of graphene on the Cu substrate is transferred by using a chemical etching and wet transfer method.

[0060] For example, the process of growing a single-layer graphene on a Cu substrate by CVD (Chemical Vapor Deposition) is as follows: the copper foil is cut into a suitable size, ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 to 30 minutes, and then annealed in a mixed gas flow of H2 and Ar at 300 to 500°C for 1 to 2 hours; the treated copper foil is placed in the center of a quartz tube and evacuated to 10 -3 ~10 -5 Pa, and replaced with Ar multiple times; the CVD temperature is increased to 800-1100°C, and Ar is continuously introduced at a flow rate of 50-500ml / min during the heating process; after reaching the set temperature, CH4 is introduced at a flow rate of 1-100ml / min and H2 is introduced at a flow rate of 10-100ml / min, and the Ar flow rate is adjusted at the same time to keep the total pressure of the system at 10-1000Pa for growth, and the growth time is 10-60min; after the growth is completed, the carbon source and H2 are stopped, and Ar is continued to be introduced, and the sample is taken out after being cooled to room temperature at a rate of 10-100°C / min; PMMA is spin-coated on the surface to protect the single-layer graphene.

[0061] The single-layer graphene is transferred to the surface of the first processing substrate by a wet transfer technology. Specifically, the wet transfer technology includes the following steps:

[0062] S201: placing the copper substrate on which the single-layer graphene is grown in a 1 mol / L ferric chloride solution and soaking for 40 to 50 min (preferably 45 min) so that the single-layer graphene can be suspended in the ferric chloride solution;

[0063] S202: transferring the single-layer graphene in the ferric chloride solution to deionized water, soaking it for 8 to 10 minutes (preferably 10 minutes), and then transferring it to clean deionized water and soaking it again, and repeating this three times;

[0064] S203: Place the first processed substrate into the deionized water solution on which the single-layer graphene floats at the end of S202 to pick up the single-layer graphene, then place the first processed substrate coated with the single-layer graphene into an oven for drying for 50 to 60 minutes (preferably 60 minutes), and then transfer it to an acetone solution and soak it for 50 to 60 minutes (preferably 60 minutes) to remove the PMMA spin-coated on the surface, so as to obtain a second processed substrate.

[0065] Single-layer graphene is a two-dimensional material with unique physical properties, namely, there are no dangling bonds on its surface. Therefore, a single-layer graphene is inserted between the substrate and the epitaxial material, that is, an intermediate layer (that is, a single-layer graphene layer) is inserted between the substrate and the epitaxial material to reduce the lattice mismatch and thermal mismatch between the substrate and the epitaxial material.

[0066] In the step S300, the liquid in the liquid containing the epitaxial layer promoting the nucleation of nanowires is preferably deionized water, and the epitaxial layer promoting the nucleation of nanowires is evenly distributed in the liquid. GaN nanowires are grown on a sapphire substrate using MOCVD technology; the epitaxial wafer with the nanowires grown is placed in a beaker filled with deionized water and shaken with an ultrasonic machine to obtain deionized water containing the epitaxial layer promoting the nucleation of nanowires.

[0067] For example, when the epitaxial layer is gallium nitride, deionized water containing gallium nitride microwires is sucked with a rubber-tipped dropper, sprayed evenly on the second processing substrate, and dried in an oven at 90° C. for 30 minutes to obtain a substrate to be epitaxially grown. By evenly spraying deionized water containing gallium nitride nanowires on the second processing substrate, the nucleation points of gallium nitride can be increased, the epitaxial growth temperature can be reduced, and the two-dimensional material layer can be protected.

[0068] The width of the nanowire is 3 to 5 μm and the length is less than 50 μm. If the nanowire is too long or too wide, it will cause the nucleation points to accumulate, which will easily destroy the single-layer graphene on the surface; while if it is too short or too narrow, it cannot serve as an effective nucleation point. In addition, the nucleation points of gallium nitride nanowires can effectively reduce the epitaxial temperature and lattice mismatch, and improve the epitaxial quality.

[0069] By classifying the m-plane sapphire substrate according to the BOW value, the back of the classified substrate is treated with chemical mechanical polishing for different times, so that the stress of the substrate can be redistributed and evenly distributed, so that the substrate and the epitaxy can form a better fit and reduce the polarization electric field in the epitaxial material. Then, a sulfuric acid / phosphoric acid mixture is used to repair the surface of the polished substrate to reduce the defects on the substrate surface, thereby reducing the influence of the substrate on the epitaxy and further reducing the stress of the epitaxial layer. By inserting a single layer of graphene, the lattice mismatch and thermal mismatch between the substrate and the epitaxial material are reduced, and the epitaxial material can be effectively stripped. Gallium nitride microwires are further used to reduce the damage of high temperature to the single layer of graphene.

[0070] When epitaxial growth is carried out on the substrate after classification, grinding and surface repair, the stress generated by the substrate during the epitaxial growth process will be reduced. By effectively classifying the substrate and grinding it to different degrees according to the classification standards, the stress in the substrate can be evenly distributed. Further chemical surface repair is used to achieve better adaptation with the epitaxy, reduce the stress generated by mismatch during the epitaxy process, and make the epitaxial structure less stressed during the growth process, so as to regulate the stress from the source.

[0071] The substrate processed by the substrate processing method of the present invention can be effectively adapted to the epitaxial layer, and can effectively reduce the occurrence of warping, cracking and the like during the epitaxial process, thereby improving the product yield.

[0072] The present invention also discloses an epitaxial growth method, such as Figure 2 As shown, the following steps are included:

[0073] Z100: providing a substrate to be epitaxially grown obtained by the above processing method;

[0074] Z200: placing the substrate to be epitaxially grown into an epitaxial furnace for epitaxial growth, and depositing an epitaxial layer 50;

[0075] Z300: depositing a functional layer 60 on the epitaxial layer.

[0076] In the step Z200, the epitaxial layer structure includes but is not limited to PD, LED and Hemt. Exemplarily, the epitaxial layer includes a stacked u-GaN layer (growth temperature of 400-600°C, thickness of 2-5μm), an n-GaN layer (growth temperature of 1000-1100°C, thickness of 2-5μm), an MQW layer (growth temperature of 600-1000°C, thickness of 10-500nm), a p-AlGaN layer (growth temperature of 800-1000°C, thickness of 50-100nm) and a p-GaN layer (growth temperature of 800-1000°C, thickness of 200-500nm). Among them, u-GaN is a healing layer, n-GaN is an electron transport layer, MQW is a composite layer, p-AlGaN is a barrier layer, and p-GaN is a hole transport layer.

[0077] The substrate to be epitaxially grown is placed in an epitaxial furnace, and MOCVD (Metal-organic Chemical Vapor Deposition) technology is used for epitaxial growth. Specifically, at 500-1100°C, hydrogen is used as a carrier gas, trimethyl gallium, triethyl gallium, trimethyl aluminum or ammonia is used as a reaction source, and u-GaN structure growth is performed on the substrate to be epitaxially grown, with a growth rate of 2.2μm / h. Preferably, the gallium nitride epitaxial layer is grown at a low temperature of 400-600°C (preferably 480°C). On the one hand, it can protect the single-layer graphene; on the other hand, due to the presence of the nucleation points of the gallium nitride nanowires, the thickness of u-GaN can be effectively reduced to 2-5μm (preferably 3μm).

[0078] n-GaN is grown on u-GaN, with a thickness of 2 to 5 μm (preferably 2 to 3 μm) and an electron doping concentration of 3 to 8×10 18 / cm 3 (Preferably 5×10 18 / cm 3 ).

[0079] A multi-quantum well layer (MQW) is further grown on the n-GaN, wherein the MQW period is 6, the InGaN well layer has a thickness of 2 to 4 nm, and the GaN barrier layer has a thickness of 10 to 15 nm.

[0080] A p-AlGaN layer of 50 to 100 nm (preferably 15 to 30 nm) is grown on the MQW layer, and the Al composition is 10 to 30% (preferably 15%).

[0081] Then grow 200-500nm (preferably 200-300nm) p-GaN on it, with a p-type doping concentration of 3-8×10 17 / cm 3 (Preferably 4.5×1017 / cm 3 ).

[0082] In step Z300, when the prepared epitaxial structure is applied in the field of LED, the functional layer is an LED functional layer, and the metal electrode is deposited by evaporation. Specifically, photolithography and inductively coupled plasma etching (ICP) are used to etch the p-GaN, p-AlGaN, and MQW to expose the n-type GaN layer, and the first and second electrodes are deposited on the p / n-type GaN, respectively. Thermal evaporation is selected to sputter (Ti / Al / Ti / Au) metal on the functional layer using a mask to form the first and second electrodes.

[0083] The present invention also provides an epitaxial structure, such as Figure 3 As shown, including the following settings from bottom to top:

[0084] Base substrate (i.e. original substrate 20);

[0085] A single graphene layer 30 having a thickness of 0.4 to 1.5 nm;

[0086] Nanowire layer 40;

[0087] Epitaxial layer 50;

[0088] Functional layer 60.

[0089] That is, the single-layer graphene layer 30 is deposited on the base substrate, the nanowire layer 40 is disposed on the single-layer graphene layer 30 , the epitaxial layer 50 is deposited on the nanowire layer 40 , and the functional layer 60 is deposited on the epitaxial layer 50 .

[0090] The single-layer graphene layer and the nanowire layer are formed on the base substrate by a substrate processing method for epitaxial growth, and the epitaxial layer and the functional layer are further formed by an epitaxial growth method. The specific processing method and growth method are specifically described in the previous text and will not be repeated here.

[0091] The substrate is the cornerstone of the epitaxial structure. The basic substrate uses a non-polar m-plane sapphire substrate to reduce the polarization electric field of the epitaxial material.

[0092] The introduction of two-dimensional materials, namely single-layer graphene, can reduce the lattice mismatch and thermal mismatch between the epitaxial material and the substrate. Due to the special physical and chemical properties of two-dimensional materials, there are no dangling bonds on their surface, so there is no lattice mismatch and thermal mismatch in the process of epitaxial nitride, which reduces the restrictions and constraints of epitaxy and enables it to grow on the m-plane. Secondly, a single-layer graphene layer can effectively regulate the stress of the epitaxial process, reduce warping and thermal mismatch during the epitaxial process, and make In doping more uniform. In addition, graphene is mainly composed of carbon, and no new impurities will be introduced during the epitaxial process, ensuring the quality of the epitaxial crystal. The epitaxial structure can be stripped by electrochemical and mechanical methods to avoid laser stripping from damaging the epitaxial structure and affecting device performance.

[0093] Introducing nanowires as nucleation points can reduce the lattice mismatch and epitaxial temperature during the epitaxial process and protect the two-dimensional materials.

[0094] [Example 1] A method for processing a substrate to be epitaxially grown is provided, comprising the following steps:

[0095] S100: Provide non-polar m-plane sapphire substrate with a size of 4 inches and a BOW value of -5. Use chemical mechanical polishing technology, colloidal silica as abrasive, polishing speed of 30r / min, pressure of 20Kpa, and polishing time of 20s;

[0096] The polished substrate was immersed in a mixed solution of 98% sulfuric acid and 85% phosphoric acid in a volume ratio of 3:1 for 30 seconds, then rinsed with DI water in an ultrasonic bath for 30 minutes, and dried to obtain a first processed substrate;

[0097] S200: placing the copper substrate with the single-layer graphene grown thereon into the prepared ferric chloride solution and soaking it for 45 minutes, then transferring the single-layer graphene suspended in the ferric chloride solution into deionized water and soaking it for 10 minutes, and rinsing is repeated three times;

[0098] Then, the first processed substrate is placed in a deionized water solution with a single-layer graphene floating thereon, the single-layer graphene is fished out, and then baked in an oven at 90° C. for 60 minutes; then, the substrate with the transferred single-layer graphene is immersed in an acetone solution for 60 minutes to obtain a second processed substrate;

[0099] S300: Use a rubber-tipped dropper to draw from the deionized water containing GaN nanowires (nanowire width is 3-5μm, length is less than 50μm), spray evenly on the second processed substrate, and use an oven to bake at 90°C for 30 minutes to obtain a substrate to be epitaxially grown (referred to as the experimental group substrate).

[0100] [Example 2] An epitaxial growth method is provided, comprising the following steps:

[0101] Z100: providing the experimental group substrate obtained in Example 1 and providing the control group substrate;

[0102] The control group substrate is an original substrate without any treatment;

[0103] Z200: The experimental substrate and various control substrates were placed in the epitaxial furnace respectively. Using MOCVD technology, at 1100°C, hydrogen was used as the carrier gas, trimethylgallium, triethylgallium, trimethylaluminum, ammonia, etc. were used as the reaction source, and the u-GaN epitaxial layer was grown at 480°C to 3μm. On the u-GaN, n-GaN was grown at 1100°C, with a thickness of 2μm and a doping concentration of 5×10 18 / cm 3 ; A multi-quantum well layer is further grown on the n-GaN at a growth temperature of 780°C, with 6 MQW periods, 2nm thick InGaN well layer and 12nm GaN barrier layer; 20nm p-AlGaN is grown on the MQW layer, with an Al component of 15% and a growth temperature of 900°C. A further 200nm p-GaN is grown on it, with a p-type doping concentration of 4.5×10 17 / cm 3； ;

[0104] Z300: Then use photolithography and ICP to etch p-GaN, p-AlGaN, and MQW to expose the n-type GaN layer, and deposit the first and second electrodes on the p / n-type GaN respectively. Use thermal evaporation to sputter (Ti / Al / Ti / Au) metal on the functional layer using a mask to form the first and second electrodes. Obtain epitaxial structures with the experimental group substrate and the control group substrate as substrates, respectively, which are called the experimental group epitaxial structure and the control group epitaxial structure.

[0105] from Figure 4 The XRD results show that the (002) and (102) of the epitaxial GaN structure of the experimental substrate are significantly smaller than those of the control structure; Figure 5 The SEM image shows that the GaN surface is smooth and flat, with no obvious defects and pits, and the crystal quality is good; Figure 6 The PL shows that its STD is 1.148 and the wavelength uniformity is excellent. The above results prove that the results obtained by the experimental substrate are better than those of the control experiment, indicating that the method provided by the present invention is very beneficial for epitaxy of high-quality nitride.

[0106] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for processing a substrate to be epitaxially grown, characterized in that: The following steps are involved: S100: providing an original substrate, grinding the back of the substrate to evenly distribute stress in the original substrate, and performing surface repair to obtain a first processed substrate; S200: providing a single-layer graphene, and transferring the single-layer graphene to a surface of a first processed substrate to obtain a second processed substrate; S300: providing a liquid containing epitaxial layer-promoting nucleation nanowires, and evenly applying the liquid on a second processing substrate, and drying to obtain a substrate for epitaxial growth.

2. The substrate processing method according to claim 1, characterized in that: The original substrate is classified by its related parameters, and then the back of the original substrate is properly ground by chemical mechanical polishing technology to prepare for uniform stress distribution in the substrate; The relevant parameter is one of BOW, Warp, TTV, and LTV.

3. The substrate processing method according to claim 2, characterized in that: The chemical mechanical polishing technology adopts a polishing speed of 10 to 100 r / min and a pressure range of 10 to 50 Kpa; The grinding time is adapted to the classification of the original substrate.

4. The substrate processing method according to claim 3, characterized in that: The original substrate is divided into 5 grades according to the BOW value range of -10 to 0, with 2 as the segment interval; The polishing speed used in chemical mechanical polishing technology is 30r / min and the pressure is 20Kpa. When the BOW value of the original substrate is between -10 and -8, the polishing time is controlled at 30s; when the BOW value of the original substrate is between -8 and -6, the polishing time is controlled at 25s; when the BOW value of the original substrate is between -6 and -4, the polishing time is controlled at 20s. When the BOW value of the original substrate is between -4 and -2, the grinding time is controlled at 15 seconds; when the BOW value of the original substrate is between -2 and 0, the grinding time is controlled at 10 seconds.

5. The substrate processing method according to claim 1, characterized in that: The surface repair is to place the ground substrate into an acidic liquid for immersion.

6. The substrate processing method according to claim 1, characterized in that: The single-layer graphene is grown on the Cu substrate by using a CVD method, and then the single-layer graphene on the Cu substrate is transferred to the surface of the first processing substrate by using a chemical etching and wet transfer method.

7. The substrate processing method according to claim 1, characterized in that: The nanowire has a width of 3 to 5 μm and a length of less than 50 μm.

8. An epitaxial growth method, characterized in that: The following steps are involved: Z100: providing a substrate to be epitaxially grown obtained by any substrate processing method according to claim 1 to 7; Z200: placing the substrate to be epitaxially grown into an epitaxial furnace for epitaxial growth and depositing the epitaxial layer; Z300: Deposition of functional layers on the epitaxial layer.

9. The epitaxial growth method according to claim 8, characterized in that: The epitaxial layer includes a u-GaN layer, an n-GaN layer, an MQW layer, a p-AlGaN layer and a p-GaN layer which are stacked.

10. An epitaxial structure, characterized in that: Including from bottom to top: base substrate; Single graphene layer; Nanowire layer; Epitaxial layer; Functional layer.

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