Substrate pretreatment methods and semiconductor epitaxial layer growth methods

Abstract

This invention discloses a substrate pretreatment method and a semiconductor epitaxial layer growth method. The pretreatment method includes: coating a substrate with a group III metal-organic source under a protective atmosphere to obtain a group III metal-organic source coating layer; then placing the substrate in an MOCVD reaction chamber, introducing the group III metal-organic source, and heat-treating it under a reducing gas atmosphere; after cooling, introducing a nitrogen source for nitriding treatment to obtain a substrate surface with single-atom-level flatness. This invention also discloses a method for sequentially growing a buffer layer and a semiconductor epitaxial layer on the substrate surface with single-atom-level flatness. This invention, by coating the substrate surface with a group III metal-organic source coating layer combined with heat treatment and nitriding treatment, obtains a substrate surface with single-atom-level flatness and can also provide nucleation centers for the growth of the buffer layer, thereby improving the flatness of the grown semiconductor epitaxial layer surface.

Description

Technical Field

[0001] This invention relates to a substrate pretreatment method and a semiconductor epitaxial layer growth method, belonging to the field of semiconductor material preparation technology. Background Technology

[0002] Wide-bandgap GaN-based semiconductor materials can be used to fabricate high-frequency, high-power, and high-temperature resistant microelectronic devices, enabling optoelectronic devices with emission wavelengths covering the entire visible light band. They have enormous application prospects in aerospace and military fields as well as commercial fields such as everyday lighting and displays.

[0003] Currently, GaN-based semiconductor materials are all grown using epitaxial technology on heterogeneous substrates. Due to the lattice and thermal expansion mismatch between the substrate and the epitaxial layer, the dislocation density and stress of the epitaxially grown crystal material are relatively high, which easily leads to warping cracks and other phenomena, affecting the operating efficiency and lifespan of the device and restricting its application in the semiconductor electronics field. The lack of matching substrates makes the growth of GaN epitaxial materials very difficult. In addition, with the development of markets such as semiconductor lighting and displays, the demand for substrates is increasingly shifting to larger sizes, which poses even greater difficulties and challenges to the growth of GaN materials.

[0004] Studies have shown that pretreatment by cleaning the substrate can achieve atomically flat substrate surfaces, improving the flatness of GaN epitaxial layers. HVPE has widely adopted chemical beam cleaning to treat the substrate with GaCl3 before growth, while MBE uses Ga atoms to clean the sapphire substrate, significantly improving the flatness of the substrate surface. However, the conventional mature MOCVD heteroepitaxial growth of buffer layers at low temperatures and GaN epitaxial layers at high temperatures is difficult to overcome the surface conditions of heteroepitaxial substrates, affecting the initial growth mode of GaN, as well as the flatness of the epitaxial layer surface and the crystal quality. Summary of the Invention

[0005] The main objective of this invention is to provide a substrate pretreatment method for improving the crystal quality of semiconductor materials, and a semiconductor epitaxial layer growth method, which can be adapted to large-size substrates to overcome the shortcomings of existing technologies.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides a substrate pretreatment method, comprising:

[0008] Under a protective atmosphere, a group III metal-organic source is coated onto a substrate to obtain a group III metal-organic source coating layer.

[0009] The substrate with the group III metal-organic source coating was then placed in the MOCVD reaction chamber, and the group III metal-organic source was introduced. The temperature was raised to 900-1200°C in a reducing gas atmosphere, and the substrate with the group III metal-organic source coating was heat-treated for 5-60 seconds.

[0010] A group III metal-organic source is continuously introduced and the temperature is lowered to 450–750°C and held stably for 15–45 seconds. Then, a nitrogen source is introduced for nitriding treatment for 60–150 seconds to obtain a substrate surface with a flatness at the single-atom level.

[0011] In some embodiments, the group III elements contained in the group III metal-organic source include any one or a combination of two or more of indium, gallium, and aluminum.

[0012] Embodiments of the present invention also provide a substrate with flatness at the single-atom level prepared by the aforementioned method.

[0013] This invention also provides a method for growing a semiconductor epitaxial layer, characterized by comprising:

[0014] The substrate is pretreated according to the aforementioned method to obtain a substrate surface with flatness at the single-atom level;

[0015] A buffer layer is epitaxially grown on the substrate surface with the flatness of the single-atom layer; and,

[0016] A semiconductor epitaxial layer is obtained by continuing epitaxial growth on the buffer layer.

[0017] Furthermore, the material of the buffer layer includes at least one of GaN, AlN, AlGaN, InGaN, etc.

[0018] Furthermore, the material of the semiconductor epitaxial layer includes at least one of GaN, AlN, AlGaN, InGaN, InN, AlInN, and AlInGaN.

[0019] In some embodiments, the growth method specifically includes:

[0020] A buffer layer with a thickness of 15-105 nm is epitaxially grown on the surface of the substrate with the flatness of the single atomic layer. The growth atmosphere required for the growth is H2 atmosphere, the growth temperature is 500-900℃, and the growth pressure is 200-600 torr.

[0021] A semiconductor epitaxial layer with a thickness of 20–10000 nm is obtained by continuing epitaxial growth on the buffer layer at a growth temperature of 500–1200 °C and a growth pressure of 50–500 torr.

[0022] The present invention also provides a semiconductor epitaxial layer prepared by the aforementioned method, wherein the surface flatness of the semiconductor epitaxial layer is less than 0.25 nm.

[0023] Compared with the prior art, the present invention has significant advantages and beneficial effects, specifically reflected in the following aspects:

[0024] 1) This invention obtains a substrate surface with single-atom-level flatness by coating a group III metal organic source coating layer, combined with heat treatment and nitriding processes, thereby improving the flatness of the semiconductor epitaxial layer surface grown on this basis.

[0025] 2) The substrate of the present invention with a group III metal-organic source coating is treated by a nitriding process, which can provide nucleation centers for the growth of the buffer layer, thereby improving the quality of the semiconductor material crystal;

[0026] 3) In this invention, the heat treatment to nitriding process utilizes the continuous introduction of a group III metal organic source during the cooling process to shield the substrate surface defects and reduce the extension of defects during the epitaxial layer growth process.

[0027] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing specific embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the semiconductor epitaxial layer fabrication process in a typical embodiment of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. Based on the embodiments of the present invention, those skilled in the art should understand that modifications can still be made to the technical solutions of each embodiment, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. All other embodiments obtained without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, directional and ordinal terms are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0032] The following will provide a further explanation of the technical solution, its implementation process, and its principles.

[0033] One aspect of the present invention provides a substrate pretreatment method comprising:

[0034] Under a protective atmosphere, a group III metal-organic source is coated onto a substrate to obtain a group III metal-organic source coating layer.

[0035] The substrate with the group III metal-organic source coating was then placed in the MOCVD reaction chamber, and the group III metal-organic source was introduced. The temperature was raised to 900-1200°C in a reducing gas atmosphere, and the substrate with the group III metal-organic source coating was heat-treated for 5-60 seconds.

[0036] A group III metal-organic source is continuously introduced and the temperature is lowered to 450–750°C and held stably for 15–45 seconds. Then, a nitrogen source is introduced for nitriding treatment for 60–150 seconds to obtain a substrate surface with a flatness at the single-atom level.

[0037] In some embodiments, the group III elements contained in the group III metal-organic source include any one or a combination of two or more of indium (In), gallium (Ga), and aluminum (Al).

[0038] Furthermore, the group III metal-organic source includes a group III organic compound source, which includes any one or a combination of two or more of indium, gallium, and aluminum sources.

[0039] The indium (In) source includes one or more combinations of trimethylindium, triethylindium, dimethylethylindium, etc., but is not limited to these.

[0040] Furthermore, the gallium (Ga) source includes one or more combinations of trimethylgallium (TMG), triethylgallium, triisopropylgallium, etc., but is not limited thereto.

[0041] Furthermore, the aluminum source includes any one or a combination of two or more of trimethylaluminum, triethylaluminum, dimethylalkanedaluminum, dimethylaluminum hydride, aluminum alkyl complexes, etc., but is not limited thereto.

[0042] Furthermore, the reducing gas preferably includes H2, but is not limited thereto.

[0043] Furthermore, the nitrogen source includes NH3, organic nitrogen sources, etc., and the organic nitrogen source includes any one or a combination of two or more of tert-butylamine, n-propylamine, dimethyl sulfide, etc., but is not limited thereto.

[0044] Furthermore, the thickness of the group III metal-organic source coating layer is 20 nm to 2000 nm.

[0045] In some preferred embodiments, the substrate pretreatment method specifically includes:

[0046] 1) Provide a substrate, the substrate being made of materials including sapphire, silicon carbide, or silicon;

[0047] 2) In an N2 atmosphere, the group III metal-organic source is spin-coated onto the substrate at a rotation speed of 400 to 4000 rpm for a spin-coating time of 15 to 150 s, forming a group III metal-organic source coating layer with a thickness of 20 nm to 2000 nm on the substrate.

[0048] 3) Place the substrate with the group III metal-organic source coating in the MOCVD reaction chamber, introduce the group III metal-organic source, heat it to 900-1200°C in a reducing gas atmosphere, and heat the substrate with the group III metal-organic source coating for 5-60 seconds.

[0049] 4) Continuously introduce a group III metal-organic source and cool it to 450-750℃, maintain it stably for 15-45s, and then introduce a nitrogen source for nitriding treatment for 60-150s to obtain a substrate surface with a flatness at the single-atom level.

[0050] In some more specific implementations, the substrate pretreatment method may further include:

[0051] Under a protective atmosphere, a group III metal-organic source is coated onto a substrate to obtain a group III metal-organic source coating layer.

[0052] The substrate with the group III metal-organic source coating is then placed in the MOCVD reaction chamber, the group III metal-organic source is introduced, and the temperature is raised to 1000-1200°C in a reducing gas atmosphere and held for 3-5 seconds. The substrate with the group III metal-organic source coating is then heat-treated for 5-10 seconds.

[0053] Continuously introduce a group III metal-organic source, cool down to 900-1000℃, maintain the temperature for 5-10 seconds, turn off the group III metal-organic source, and then introduce a nitrogen source for nitriding treatment for 10-30 seconds;

[0054] Next, the nitrogen source was turned off, and then a group III metal-organic source was introduced. The temperature was lowered to 750–900°C and held for 10–15 seconds. The group III metal-organic source was then turned off, and then the nitrogen source was introduced again for nitriding treatment for 30–50 seconds.

[0055] Then the nitrogen source is turned off, a group III metal-organic source is continuously introduced, and the temperature is lowered to 450–750°C and held for 15–45 seconds. Then the nitrogen source is introduced again for nitriding treatment for 60–150 seconds to obtain a substrate surface with a flatness at the single-atom level.

[0056] Another aspect of this invention provides a substrate with single-atom-level flatness prepared by the aforementioned method. This pretreated substrate can provide nucleation centers for the growth of a buffer layer, thereby improving the flatness of the surface of the semiconductor epitaxial layer grown thereon.

[0057] Another aspect of the present invention provides a method for growing a semiconductor epitaxial layer, comprising:

[0058] The substrate is pretreated according to the aforementioned method to obtain a substrate surface with flatness at the single-atom level;

[0059] A buffer layer is epitaxially grown on the substrate surface with the flatness of the single-atom layer; and,

[0060] A semiconductor epitaxial layer is obtained by continuing epitaxial growth on the buffer layer.

[0061] For more specific implementation examples, please refer to Figure 1 As shown, the method for preparing the semiconductor epitaxial layer specifically includes the following steps:

[0062] A) Provide a substrate, said substrate being sapphire, silicon carbide, or silicon, etc.;

[0063] B) In an N2 atmosphere, the group III metal-organic source is spin-coated onto the substrate at a rotation speed of 400 to 4000 rpm for a spin-coating time of 15 to 150 s, forming a group III metal-organic source coating layer with a thickness of 20 nm to 2000 nm on the substrate.

[0064] C) Place the substrate with a group III metal-organic source coating in the MOCVD reaction chamber. The pressure in the reaction chamber is 50-600 torr. Introduce the group III metal-organic source and heat it to 900-1200°C in a reducing gas atmosphere. Heat the substrate with the group III metal-organic source coating for 5-60 seconds.

[0065] D) Continuously introduce a group III metal-organic source and cool it to 450-750℃, hold it stably for 15-45s, then introduce a nitrogen source for nitriding treatment for 60-150s to obtain a substrate surface with a flatness at the single-atom level, which can provide nucleation centers for the growth of the buffer layer, thereby improving the quality of semiconductor material crystals.

[0066] E) Epitaxially grow a buffer layer with a thickness of 15-105 nm on the surface of the substrate with flatness at the single atomic level. The growth atmosphere required for growth is H2 atmosphere, the growth temperature is 500-900℃, and the growth pressure is 200-600 torr.

[0067] F) Continue epitaxial growth on the buffer layer to obtain a semiconductor epitaxial layer with a thickness of 20-10000 nm, with a growth temperature of 500-1200 °C and a growth pressure of 50-500 torr.

[0068] In some specific implementation cases, taking MO sources as an example, a method for preparing a GaN-based epitaxial layer on a substrate by spin-coating and cleaning an epitaxial substrate with a MO source mainly includes: preparing a MO source spin-coating layer by spin-coating a MO source on the substrate, then epitaxially growing a buffer layer, and finally growing a GaN-based material epitaxial layer on the buffer layer, specifically including the following steps:

[0069] (1) Under N2 atmosphere, a MO source is spin-coated onto a substrate to prepare a MO source spin coating layer;

[0070] (2) The spin coating was heat-treated and nitrided using MOCVD epitaxy technology, and then a buffer layer was grown.

[0071] (3) Continue to use MOCVD technology to grow GaN-based epitaxial layers on the buffer layer.

[0072] Further, in step (1), a MO source is spin-coated onto the substrate to prepare a MO source spin coating layer, wherein the MO source can be any one or more of TMG, TEG, TMA1, and TEA1. The spin-coating method used in this invention to prepare the MO source spin coating layer is simple and has strong process controllability.

[0073] In some embodiments, the material of the buffer layer grown on the substrate in step (2) may include at least one of GaN, AlN, AlGaN, InGaN, etc., but is not limited thereto.

[0074] More specifically, the buffer layer can be a low-temperature buffer layer, which can be a single layer or multiple layers, and a medium-temperature buffer layer can be epitaxially grown on the basis of the low-temperature buffer layer.

[0075] In some embodiments, the semiconductor epitaxial layer grown on the buffer layer in step (3) may be a GaN-based epitaxial layer, and its material may include at least one of GaN, AlN, AlGaN, InGaN, InN, AlInN, AlInGaN, etc., but is not limited thereto.

[0076] Furthermore, the material of the semiconductor epitaxial layer includes at least one of unintentionally doped nitride epitaxial layer (such as unintentionally doped GaN-based epitaxial layer), n-type nitride epitaxial layer (such as n-type GaN-based epitaxial layer), and p-type nitride epitaxial layer (such as p-type GaN-based epitaxial layer), but is not limited thereto.

[0077] The method for improving the crystal quality of MOCVD-grown semiconductor materials provided above is applicable to large-size substrates.

[0078] Another aspect of the present invention provides a semiconductor epitaxial layer prepared by the aforementioned method, wherein the surface flatness of the semiconductor epitaxial layer is less than 0.25 nm.

[0079] In summary, this invention pretreats the substrate by coating a group III metal organic source coating layer combined with heat treatment and nitriding treatment to obtain a substrate surface with flatness at the single-atom level. It can also provide nucleation centers for the growth of buffer layers, thereby improving the flatness of the semiconductor epitaxial layer surface grown on this basis.

[0080] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. The detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0081] Example 1

[0082] Under N2 atmosphere, a TMG (trimethylgallium) source was spin-coated on a sapphire substrate at a speed of 400 rpm for 15 s, and a TMG source spin coating with a thickness of 2000 nm was prepared.

[0083] Using MOCVD technology, a sapphire substrate with a TMG source swirl coating is placed in an MOCVD reaction chamber, the pressure is set to 600 torr, a TMG source is introduced, and the reaction chamber is heated to 1000°C in an H2 atmosphere to perform heat treatment on the sapphire substrate with the TMG source swirl coating for 15 seconds.

[0084] A TMG source was continuously introduced into the reaction chamber and cooled to 450°C. The temperature was maintained for 45 seconds, and then NH3 was introduced for nitriding treatment. The nitriding treatment time was 100 seconds, resulting in a substrate surface with a flatness at the single-atom level.

[0085] Turn on the TMG source and grow a 105 nm thick low-temperature GaN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 565℃, and the growth pressure is 600 torr.

[0086] An unintentionally doped GaN epitaxial layer with a thickness of 10 μm was grown on a low-temperature GaN buffer layer at a growth temperature of 1100 °C and a growth pressure of 300 torr.

[0087] Example 2

[0088] Under N2 atmosphere, a TMG (trimethylgallium) source was spin-coated on a sapphire substrate at a speed of 400 rpm for 100 s to prepare a TMG source spin coating with a thickness of 800 nm.

[0089] Using MOCVD technology, a sapphire substrate with a TMG source swirl coating is placed in an MOCVD reaction chamber, the pressure is set to 400 torr, a TMG source is introduced, and the reaction chamber is heated to 1100°C in an H2 atmosphere to perform heat treatment on the sapphire substrate with the TMG source swirl coating for 10 seconds.

[0090] A TMG source was continuously introduced into the reaction chamber and cooled to 500°C. The temperature was maintained for 35 seconds, and then NH3 was introduced for nitriding treatment. The nitriding treatment time was 65 seconds, resulting in a substrate surface with a flatness at the single-atom level.

[0091] Turn on the TMG source and grow a 45nm thick low-temperature GaN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 545℃, and the growth pressure is 400 torr.

[0092] An unintentionally doped GaN epitaxial layer with a thickness of 5 μm was grown on a low-temperature GaN buffer layer at a growth temperature of 1110 °C and a growth pressure of 200 torr.

[0093] Example 3

[0094] Under N2 atmosphere, a TMG (trimethylgallium) source was spin-coated on a sapphire substrate at a speed of 400 rpm for 100 s to prepare a TMG source spin coating with a thickness of 200 nm.

[0095] Using MOCVD technology, a sapphire substrate with a TMG source swirl coating is placed in an MOCVD reaction chamber, the pressure is set to 200 torr, a TMG source is introduced, and the reaction chamber is heated to 1200°C in an H2 atmosphere to perform heat treatment on the sapphire substrate with the TMG source swirl coating for 5 seconds.

[0096] A TMG source was introduced into the reaction chamber and cooled to 550°C. The temperature was maintained for 30 seconds, and then NH3 was introduced for nitriding treatment. The nitriding treatment time was 85 seconds, resulting in a substrate surface with a flatness at the single-atom level.

[0097] Turn on the TMG source and grow a 20 nm thick low-temperature GaN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 545℃, and the growth pressure is 400 torr.

[0098] An unintentionally doped GaN epitaxial layer with a thickness of 1.5 μm was grown on a low-temperature GaN buffer layer at a growth temperature of 1120 °C and a growth pressure of 200 torr.

[0099] Examples 1, 2, and 3 respectively prepared GaN epitaxial layers of different thicknesses, with dislocation densities of 3.5 × 10⁻⁶. 8 cm -2 2.4×10 8 cm -2 and 1.1×10 8 cm -2 The average surface roughness of the AFM test surface was less than 0.25 nm.

[0100] Example 4

[0101] Under N2 atmosphere, a TMAl (trimethylaluminum) source was spin-coated onto a sapphire substrate at a speed of 2000 rpm for 100 s to prepare a TMAl source spin coating with a thickness of 250 nm.

[0102] Using MOCVD technology, a sapphire substrate with a TMAl source spin coating is placed in an MOCVD reaction chamber, the pressure is set to 200 torr, a TMAl source is introduced, and the reaction chamber is heated to 1050°C in an H2 atmosphere to perform heat treatment on the sapphire substrate with the TMAl source spin coating for 10 seconds.

[0103] A TMAl source was introduced into the reaction chamber and cooled to 650°C. The temperature was maintained for 20 seconds, and then NH3 was introduced for nitriding treatment. The nitriding treatment time was 100 seconds, resulting in a substrate surface with a flatness at the single-atom level.

[0104] Turn on the TMAl source and grow a 25nm thick low-temperature AlN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 680℃, and the growth pressure is 250 torr.

[0105] An unintentionally doped AlN epitaxial layer with a thickness of 0.2 μm was grown on a low-temperature AlN buffer layer at a growth temperature of 1200 °C and a growth pressure of 150 torr.

[0106] Example 5

[0107] Under N2 atmosphere, a TMAl (trimethylaluminum) source was spin-coated onto a sapphire substrate at a speed of 2000 rpm for 100 s to prepare a TMAl source spin coating with a thickness of 250 nm.

[0108] Using MOCVD technology, a sapphire substrate with a TMAl source spin coating is placed in an MOCVD reaction chamber, the pressure is set to 400 torr, a TMAl source is introduced, and the reaction chamber is heated to 950°C in an H2 atmosphere to perform heat treatment on the sapphire substrate with the TMAl source spin coating for 40 seconds.

[0109] A TMAl source was introduced into the reaction chamber and cooled to 600°C. The temperature was maintained for 25 seconds, and then NH3 was introduced for nitriding treatment. The nitriding treatment time was 120 seconds, resulting in a substrate surface with a flatness at the single-atom level.

[0110] Turn on the TMAl source and grow a 25nm thick low-temperature AlN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 680℃, and the growth pressure is 200 torr.

[0111] A medium-temperature AlN buffer layer with a thickness of 100 nm was grown on a low-temperature AlN buffer layer. The growth atmosphere was H2, the growth temperature was 900℃, and the growth pressure was 200 torr.

[0112] An AlN epitaxial layer with a thickness of 0.5 μm was grown on a medium-temperature AlN buffer layer at a growth temperature of 1200 °C and a growth pressure of 100 torr.

[0113] In Examples 4 and 5, high-quality AlN epitaxial layers were prepared, with a half-width of less than 150 mm in the X-ray diffraction (0002) swing curve and an average surface roughness of less than 0.25 nm in the AFM test.

[0114] Example 6

[0115] Under N2 atmosphere, a TMAl (trimethylaluminum) source was spin-coated onto a sapphire substrate at a speed of 2000 rpm for 120 s to prepare a TMAl source spin coating with a thickness of 350 nm.

[0116] Using MOCVD technology, a sapphire substrate with a TMAl source spin coating is placed in an MOCVD reaction chamber, the pressure is set to 400 torr, a TMAl source is introduced, and the reaction chamber is heated to 1100°C in an H2 atmosphere to perform heat treatment on the sapphire substrate with the TMAl source spin coating for 10 seconds.

[0117] A TMAl source was introduced into the reaction chamber and cooled to 680°C. The temperature was maintained for 20 seconds, and then NH3 was introduced for nitriding treatment. The nitriding treatment time was 75 seconds, resulting in a substrate surface with a flatness at the single-atom level.

[0118] Turn on the TMAl source and grow a 25nm thick low-temperature AlN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 680℃, and the growth pressure is 200 torr.

[0119] A medium-temperature AlN buffer layer with a thickness of 100 nm was grown on a low-temperature AlN buffer layer. The growth atmosphere was H2, the growth temperature was 900℃, and the growth pressure was 300 torr.

[0120] An AlGaN epitaxial layer with a thickness of 1.5 μm was grown on an intermediate-temperature AlN buffer layer at a growth temperature of 1200 °C and a growth pressure of 200 torr.

[0121] Example 7

[0122] Under N2 atmosphere, a TMAl (trimethylaluminum) source was spin-coated onto a sapphire substrate at a speed of 800 rpm for 110 s, and a TMAl source spin coating with a thickness of 450 nm was prepared.

[0123] Using MOCVD technology, a sapphire substrate with a TMAl source spin coating is placed in an MOCVD reaction chamber, the pressure is set to 400 torr, a TMAl source is introduced, and the reaction chamber is heated to 1150°C in an H2 atmosphere to perform heat treatment on the sapphire substrate with the TMAl source spin coating for 10 seconds.

[0124] A TMAl source was introduced into the reaction chamber and cooled to 700°C. The temperature was maintained for 15 seconds, and then NH3 was introduced for nitriding treatment. The nitriding treatment time was 80 seconds, resulting in a substrate surface with a flatness at the single-atom level.

[0125] Turn on the TMAl source and grow a 25nm thick low-temperature AlGaN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 680℃, and the growth pressure is 500 torr.

[0126] An AlGaN epitaxial layer with a thickness of 0.1 μm was grown on a low-temperature AlGaN buffer layer at a growth temperature of 500 °C and a growth pressure of 500 torr.

[0127] Examples 6 and 7 show the preparation of high-quality AlGaN epitaxial layers with a full width at half maximum (FWHM) of less than 250 for X-ray diffraction (0002) swing curves and an intact surface without cracks.

[0128] Example 8

[0129] Under N2 atmosphere, a TMIn (trimethylindium) source was spin-coated onto a sapphire substrate at a speed of 400 rpm for 100 s to prepare a TMIn source spin coating with a thickness of 1200 nm.

[0130] Using MOCVD technology, a sapphire substrate with a TMIn source spin coating is placed in an MOCVD reaction chamber, the pressure is set to 200 torr, a TMIn source is introduced, and the reaction chamber is heated to 1200°C in an H2 atmosphere to perform heat treatment on the sapphire substrate with the TMIn source spin coating for 5 seconds.

[0131] A TMIn source is introduced into the reaction chamber and cooled to 750°C. The temperature is maintained for 15 seconds, and then a dimethyl trap is introduced for nitriding treatment. The nitriding treatment time is 60 seconds to obtain a substrate surface with a flatness at the single-atom level.

[0132] Turn on the TMIn source and grow a 20nm thick low-temperature InGaN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 900℃, and the growth pressure is 600 torr.

[0133] A 20 nm thick InGaN epitaxial layer was grown on a low-temperature InGaN buffer layer at a growth temperature of 725 °C and a growth pressure of 350 torr.

[0134] Example 9

[0135] Under N2 atmosphere, a TMAl (trimethylaluminum) source was spin-coated onto a silicon carbide substrate at a speed of 1000 rpm for 150 s to prepare a TMAl source spin coating with a thickness of 100 nm.

[0136] Using MOCVD technology, a silicon carbide substrate with a TMAl source spin coating is placed in an MOCVD reaction chamber, the pressure is set to 400 torr, a TMAl source is introduced, and the reaction chamber is heated to 900°C in an H2 atmosphere to perform heat treatment on the silicon carbide substrate with the TMAl source spin coating for 60 seconds.

[0137] A TMAl source was introduced into the reaction chamber and cooled to 650°C. The temperature was maintained for 45 seconds, and then n-propylamine was introduced for nitriding treatment. The nitriding treatment time was 80 seconds, resulting in a substrate surface with a flatness at the single-atom level.

[0138] Turn on the TMAl source and grow a 25nm thick low-temperature AlN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 560℃, and the growth pressure is 500 torr.

[0139] An AlInN epitaxial layer with a thickness of 100 nm was grown on a low-temperature AlN buffer layer at a growth temperature of 780 °C and a growth pressure of 50 torr.

[0140] Example 10

[0141] Under N2 atmosphere, a TMIn (trimethylindium) source was spin-coated onto a silicon substrate at a speed of 4000 rpm for 60 s to prepare a TMIn source spin coating with a thickness of 60 nm.

[0142] Using MOCVD technology, a silicon substrate with a TMIn source spin coating is placed in the MOCVD reaction chamber, the pressure is set to 50 torr, a TMIn source is introduced, and the reaction chamber is heated to 1000°C in H2 atmosphere to perform heat treatment on the silicon substrate with the TMIn source spin coating for 5 seconds.

[0143] A TMIn source is introduced into the reaction chamber and cooled to 500°C. The temperature is maintained for 40 seconds, and then tert-butylamine is introduced for nitriding treatment. The nitriding treatment time is 150 seconds to obtain a substrate surface with a flatness at the single-atom level.

[0144] Turn on the TMIn source and grow a 15nm thick low-temperature InGaN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 500℃, and the growth pressure is 600 torr.

[0145] A 50 nm thick low-temperature InN buffer layer was grown on a low-temperature InGaN buffer layer in an H2 atmosphere at a growth temperature of 525 °C and a growth pressure of 250 torr.

[0146] A 100 nm thick InN epitaxial layer was grown on the low-temperature InN buffer layer at a growth temperature of 565 °C and a growth pressure of 450 torr.

[0147] Example 10 prepared a high-quality InN epitaxial layer with a good surface morphology, small grain size, and a mobility exceeding 1182 cm⁻¹. 2 / Vs.

[0148] Comparative Example 1

[0149] The difference between this comparative example and Example 1 is that the substrate was nitrided directly without high-temperature heat treatment.

[0150] Comparative Example 2

[0151] The difference between this comparative example and Example 1 is that only the substrate was subjected to high-temperature heat treatment, and no nitriding treatment was performed.

[0152] Comparative Example 3

[0153] The difference between this comparative example and Example 1 is that the substrate was not subjected to high-temperature heat treatment or nitriding treatment.

[0154] Through testing and analysis, it was found that the substrate obtained in Comparative Example 1, due to the lack of high-temperature heat treatment, had a high density of black spots and voids on its surface, resulting in poor continuity of the epitaxial layer surface. The substrate obtained in Comparative Example 2, due to the lack of nitriding treatment, had a rough surface, scattered black spots on the epitaxial surface, and dense hexagonal defects at the center of the epitaxial wafer. The half-peak widths of the X-ray diffraction (0002) swing curves exceeded 650 and 550 arsec, respectively. AFM testing revealed that, compared to the GaN epitaxial layer obtained in Comparative Example 3, the GaN epitaxial layers obtained in Examples 1 and 2 had a one-order-of-magnitude reduction in relative epitaxial layer defect density, improving the crystal quality of the epitaxial layer and reducing the root-mean-square roughness of the epitaxial layer surface by 8%–10%. Therefore, the above preparation process provided by this invention is simple, highly controllable, and reduces the epitaxial growth cost through the spin-coating process of the group III metal-organic source coating layer.

[0155] Example 11

[0156] In Example 3, a 2.5 μm n-type GaN layer was epitaxially grown under growth conditions of 1095 °C and 200 torr, with a doping concentration of 2 × 10⁻⁶. 18 cm -3 ;

[0157] Under growth conditions of 750–900℃ and 100–300 torr, an InGaN / GaN multi-quantum-well light-emitting layer is grown on the quantum well layer. The InGaN quantum well layer and GaN quantum barrier layer are periodically and repeatedly grown alternately, with a growth cycle of 10. The thickness of the InGaN quantum well layer is 3 nm and the thickness of the GaN quantum barrier layer is 11 nm.

[0158] A 20 nm thick p-type AlGaN layer was grown on the InGaN / GaN multi-quantum-well light-emitting layer under growth conditions of 890 °C and 150 torr.

[0159] A 60 nm p-type GaN layer was grown on the p-type AlGaN layer under growth conditions of 920 °C and 400 torr, with a doping concentration of 5 × 10⁻⁶ nm. 19 cm -3 .

[0160] Example 12

[0161] In Example 3, a 2.5 μm n-type GaN layer was epitaxially grown under growth conditions of 1095 °C and 200 torr, with a doping concentration of 2 × 10⁻⁶. 18 cm -3 ;

[0162] Under growth conditions of 720–920℃ and 100–300 torr, an InGaN / GaN multi-quantum-well light-emitting layer is grown on the quantum well layer. The InGaN quantum well layer and GaN quantum barrier layer are periodically and alternately grown, with a growth cycle of 12. The thickness of the InGaN quantum well layer is 3.5 nm, and the thickness of the GaN quantum barrier layer is 12 nm.

[0163] A 20 nm thick p-type AlGaN layer was grown on the InGaN / GaN multi-quantum-well light-emitting layer under growth conditions of 890 °C and 150 torr.

[0164] A 60 nm p-type GaN layer was grown on the p-type AlGaN layer under growth conditions of 920 °C and 400 torr, with a doping concentration of 5 × 10⁻⁶ nm. 19 cm -3 .

[0165] Comparative Example 4

[0166] The difference between Comparative Example 4 and Example 11 is that Comparative Example 4 is an epitaxial layer grown on the basis of Comparative Example 1, while the rest is the same as Example 11.

[0167] Comparative Example 5

[0168] The difference between Comparative Example 5 and Example 12 is that Comparative Example 5 is an epitaxial layer grown on the basis of Comparative Example 2, and the rest is the same as Example 12.

[0169] In Examples 11 and 12, blue (470nm) and green (520nm) LED epitaxial layers were prepared, respectively. After testing, it was found that the photoluminescence (PL) intensity was increased by 46% and 52% compared with Comparative Example 4 and Comparative Example 5, respectively, the full width at half maximum (FWHM) was 18.1 and 27.2, respectively, and the spot measurement voltage was reduced by 0.4V and 0.6V, respectively.

[0170] Example 13

[0171] Under N2 atmosphere, a TMG (trimethylgallium) source was spin-coated on a sapphire substrate at a speed of 400 rpm for 15 s, and a TMG source spin coating with a thickness of 2000 nm was prepared.

[0172] Using MOCVD technology, a sapphire substrate with a TMG source swirl coating is placed in an MOCVD reaction chamber, the pressure is set to 600 torr, a TMG source is introduced, and the reaction chamber is heated to 1000°C in an H2 atmosphere and held stably for 5s. The sapphire substrate with the TMG source swirl coating is then subjected to heat treatment for 10s.

[0173] Continuously introduce TMG source, cool down to 900℃, maintain stable temperature for 10s, turn off TMG source, and then introduce NH3 for nitriding treatment for 30s;

[0174] Next, turn off the NH3 source, then introduce the TMG source, cool down to 750℃, maintain the temperature for 15 seconds, turn off the TMG source, and then introduce NH3 for nitriding treatment for 50 seconds.

[0175] Then the NH3 source was turned off, and the TMG source was continuously introduced into the reaction chamber. The temperature was lowered to 700°C and held for 45 seconds. Then NH3 was introduced again for nitriding treatment. The nitriding treatment time was 100 seconds to obtain a substrate surface with a flatness at the single-atom level.

[0176] Turn on the TMG source and grow a 105 nm thick low-temperature GaN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 565℃, and the growth pressure is 600 torr.

[0177] An unintentionally doped GaN epitaxial layer with a thickness of 10 μm was grown on a low-temperature GaN buffer layer at a growth temperature of 1100 °C and a growth pressure of 300 torr.

[0178] Example 14

[0179] Under N2 atmosphere, a TMAl (trimethylaluminum) source was spin-coated onto a sapphire substrate at a speed of 800 rpm for 110 s, and a TMAl source spin coating with a thickness of 450 nm was prepared.

[0180] Using MOCVD technology, a sapphire substrate with a TMAl source spin coating is placed in an MOCVD reaction chamber, the pressure is set to 400 torr, a TMAl source is introduced, and the reaction chamber is heated to 1200°C in an H2 atmosphere and held stably for 3s. The sapphire substrate with the TMAl source spin coating is then subjected to heat treatment for 5s.

[0181] Continuously introduce the TMAl source, cool down to 1000℃, maintain the temperature for 5s, turn off the TMAl source, and then introduce NH3 for nitriding treatment for 10s;

[0182] Next, turn off the NH3 source, then introduce the TMAl source, cool down to 900℃, maintain the temperature for 10s, turn off the TMAl source, and then introduce NH3 for nitriding treatment for 30s.

[0183] A TMAl source was introduced into the reaction chamber and cooled to 750°C. The temperature was maintained for 15 seconds, and then NH3 was introduced for nitriding treatment. The nitriding treatment time was 80 seconds, resulting in a substrate surface with a flatness at the single-atom level.

[0184] Turn on the TMAl source and grow a 25nm thick low-temperature AlGaN buffer layer on the substrate surface. The growth atmosphere is H2 atmosphere, the growth temperature is 680℃, and the growth pressure is 500 torr.

[0185] An AlGaN epitaxial layer with a thickness of 0.1 μm was grown on a low-temperature AlGaN buffer layer at a growth temperature of 500 °C and a growth pressure of 500 torr.

[0186] In the above embodiments 13-14, the substrate is continuously processed under temperature changes, which can obtain a substrate surface with better flatness. The flatness of the epitaxial layer surface is 0.22nm and 0.25nm, respectively.

[0187] In summary, this invention obtains a substrate surface with single-atom-level flatness by coating a group III metal organic source coating layer, combined with heat treatment and nitriding processes, thereby improving the flatness of the semiconductor epitaxial layer surface grown on this basis. It can also provide nucleation centers for the growth of buffer layers, thereby improving the flatness of the grown semiconductor epitaxial layer surface.

[0188] It should be noted that the semiconductor epitaxial layer of the present invention can be used not only for LEDs, but also for HEMTs, PIN detectors, solar cells and lasers.

[0189] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all expressions falling within the meaning and scope of equivalents of the claims are intended to be included in the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for pretreating a substrate, characterized in that, include: In an N2 atmosphere, a group III metal-organic source is spin-coated onto a substrate at a speed of 400-4000 rpm for 15-150 s, forming a group III metal-organic source coating layer with a thickness of 20 nm-2000 nm on the substrate. The substrate with the group III metal-organic source coating was then placed in the MOCVD reaction chamber, and the group III metal-organic source was introduced. The temperature was raised to 900~1200℃ in a reducing gas atmosphere, and the substrate with the group III metal-organic source coating was heat-treated for 5~60s. A group III metal-organic source is continuously introduced and cooled to 450~750℃, and held stably for 15~45s to shield the defects on the substrate surface. Nitrogen source is then introduced for nitriding treatment for 60-150 seconds to provide nucleation centers for the buffer layer to be grown subsequently, and to obtain a substrate surface with flatness at the single-atom level. The group III metal-organic source includes a group III organic compound source, which includes any one or a combination of two or more of indium, gallium, and aluminum sources; the nitrogen source includes NH3 and / or an organic nitrogen source, which includes any one or a combination of two or more of tert-butylamine, n-propylamine, and dimethyl sulfide.

2. The substrate pretreatment method according to claim 1, characterized in that: The indium source includes any one or a combination of two or more of trimethylindium, triethylindium, and dimethylethylindium.

3. The substrate pretreatment method according to claim 1, characterized in that: The gallium source includes any one or a combination of two or more of trimethylgallium, triethylgallium, and triisopropylgallium.

4. The substrate pretreatment method according to claim 1, characterized in that: The aluminum source includes any one or a combination of two or more of trimethylaluminum, triethylaluminum, dimethylalkanedaluminum, dimethylaluminum hydride, and aluminum alkyl complexes.

5. The substrate pretreatment method according to claim 1, characterized in that: The reducing gas includes H2.

6. The substrate pretreatment method according to claim 1, characterized in that: The substrate is made of materials including sapphire, silicon carbide, or silicon.

7. The substrate pretreatment method according to claim 1, characterized in that, Specifically, it includes: In an N2 atmosphere, a group III metal-organic source is spin-coated onto a substrate at a speed of 400-4000 rpm for 15-150 s, forming a group III metal-organic source coating layer with a thickness of 20 nm-2000 nm on the substrate. The substrate with the group III metal-organic source coating is then placed in the MOCVD reaction chamber, the group III metal-organic source is introduced, and the temperature is raised to 1000~1200℃ in a reducing gas atmosphere and held for 3~5s. The substrate with the group III metal-organic source coating is then heat-treated for 5~10s. Continuously introduce a group III metal-organic source, cool down to 900~1000℃, maintain stable temperature for 5~10s, turn off the group III metal-organic source, and then introduce a nitrogen source for nitriding treatment for 10~30s; Next, turn off the nitrogen source, then introduce a group III metal-organic source, cool down to 750~900℃, maintain the temperature for 10~15s, turn off the group III metal-organic source, and then introduce the nitrogen source again for nitriding treatment for 30~50s. Then the nitrogen source is turned off, a group III metal-organic source is continuously introduced, and the temperature is lowered to 450~750℃ and held for 15~45s. Then the nitrogen source is introduced again for nitriding treatment for 60~150s to obtain a substrate surface with a flatness at the single-atom level.

8. A substrate with single-atom-level flatness prepared by the method of any one of claims 1-7.

9. A method for growing a semiconductor epitaxial layer, characterized in that, include: The substrate is pretreated according to any one of claims 1-7 to obtain a substrate surface with flatness at the single-atom level; A buffer layer is epitaxially grown on the substrate surface with the flatness of the single-atom layer; and, A semiconductor epitaxial layer is obtained by continuing epitaxial growth on the buffer layer.

10. The growth method according to claim 9, characterized in that: The material of the buffer layer includes at least one of GaN, AlN, AlGaN, and InGaN.

11. The growth method according to claim 9, characterized in that: The semiconductor epitaxial layer includes at least one of an unintentionally doped nitride epitaxial layer, an n-type nitride epitaxial layer, and a p-type nitride epitaxial layer.

12. The growth method according to claim 9, characterized in that: The material of the semiconductor epitaxial layer includes at least one of GaN, AlN, AlGaN, InGaN, InN, AlInN, and AlInGaN.

13. The growth method according to claim 9, characterized in that: The thickness of the semiconductor epitaxial layer is 20~10000nm.

14. The growth method according to claim 9, characterized in that, Includes the following steps: A buffer layer with a thickness of 15~105nm is epitaxially grown on the substrate surface with the flatness of the single atomic layer. The growth atmosphere required for growth is H2 atmosphere, the growth temperature is 500~900℃, and the growth pressure is 200~600 torr. A semiconductor epitaxial layer with a thickness of 20~10000nm is obtained by continuing epitaxial growth on the buffer layer, with a growth temperature of 500~1200℃ and a growth pressure of 50~500 torr.

15. A semiconductor epitaxial layer prepared by the method of any one of claims 9-14, wherein the surface flatness of the semiconductor epitaxial layer is less than 0.25 nm.

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