Epitaxial wafer preparation device and method

Abstract

The invention discloses an epitaxial wafer preparation device and method, and the device comprises a growth cavity which comprises a top part and a bottom part which are oppositely disposed, and a side part which is disposed between the top part and the bottom part; the cooling cavity is arranged outside the growth cavity in a surrounding manner; the vent holes are formed in the side part at intervals in a penetrating manner; the air inlet hole is formed in the cooling cavity; the heating piece is arranged outside the cooling cavity; and the slide holder is arranged in the growth cavity. According to the preparation device and method provided by the invention, particle foreign matters in the growth cavity can be reduced, defects in the epitaxial layer are reduced, and the quality of the epitaxial wafer is improved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide material preparation technology, and in particular to an apparatus and method for preparing epitaxial wafers. Background Technology

[0002] Silicon carbide (SiC), as a typical representative of third-generation wide-bandgap semiconductor materials, possesses excellent physicochemical properties such as a large bandgap, high critical breakdown electric field, high thermal conductivity, and fast electron saturation drift velocity, making it promising for applications in high-temperature, high-frequency, high-power, and radiation-resistant semiconductor devices. Among these, the silicon carbide epitaxial wafer obtained through homoepitaxial growth is a crucial step in fabricating high-performance silicon carbide devices. The quality of the silicon carbide epitaxial wafer determines the device's performance. However, during wafer fabrication, foreign particles within the cavity can affect epitaxial growth, leading to defects such as falling particles or triangular defects in the epitaxial layer, thus impacting the quality of the silicon carbide epitaxial wafer and consequently, the quality of the silicon carbide device. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an apparatus and method for preparing epitaxial wafers, which can reduce particulate foreign matter in the growth cavity, reduce defects in the epitaxial layer, and improve the quality of epitaxial wafers.

[0004] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution.

[0005] This invention provides an apparatus for preparing an epitaxial wafer, comprising at least:

[0006] The growth chamber includes a top and a bottom disposed opposite to each other, and a side portion disposed between the top and the bottom;

[0007] A cooling chamber is arranged around the growth chamber, and the cooling chamber and the growth chamber are spaced apart.

[0008] Multiple ventilation holes are spaced apart and arranged through the side portion;

[0009] An air inlet is provided on the cooling chamber;

[0010] A heating element is disposed outside the cooling chamber; and

[0011] A slide stage is disposed within the growth chamber.

[0012] In one embodiment of the present invention, the cooling cavity includes a top wall and a bottom wall disposed opposite to each other, the top wall being spaced apart from the top and the bottom wall being spaced apart from the bottom.

[0013] In one embodiment of the present invention, the cooling cavity further includes a sidewall, the sidewall being connected to the top wall and the bottom wall, and the sidewall and the side portion being spaced apart.

[0014] In one embodiment of the present invention, the air inlet is disposed on the bottom wall.

[0015] The present invention also proposes a method for preparing an epitaxial wafer, using the above-described preparation apparatus, comprising at least the following steps:

[0016] After placing the substrate on the stage, the pressure inside the growth chamber is reduced to the preset pressure;

[0017] Etch the surface of the substrate;

[0018] A buffer layer is formed on the surface of the substrate;

[0019] Purge gas is introduced between the cooling chamber and the growth chamber through the air inlet. The purge gas diffuses to one side of the inner wall of the growth chamber through the vent. Simultaneously, process gas is introduced into the growth chamber, heating it to the growth temperature. The process gas is deposited on the buffer layer to form an epitaxial layer.

[0020] The growth chamber is cooled to obtain an epitaxial wafer.

[0021] In one embodiment of the present invention, the flow rate of the purge gas between the cooling chamber and the growth chamber is greater than the flow rate of the purge gas on the inner wall side of the growth chamber.

[0022] In one embodiment of the present invention, the purging gas is distributed on both sides of the process gas within the growth chamber.

[0023] In one embodiment of the present invention, when etching the surface of the substrate, the growth cavity is heated to the etching temperature and etching gas is introduced into the growth cavity.

[0024] In one embodiment of the present invention, the etching temperature is 1500℃-1600℃, and the etching gas includes hydrogen and hydrogen chloride.

[0025] In one embodiment of the present invention, the volume percentage of hydrogen chloride in the etching gas is 1%-5%.

[0026] In summary, this invention provides an apparatus and method for preparing epitaxial wafers. By optimizing the apparatus and method, particulate foreign matter within the growth chamber can be removed, preventing its deposition on the substrate surface. This avoids surface morphology defects such as falling particles or triangular defects, as well as crystal structure defects such as stacking faults, significantly improving the quality of the epitaxial wafer. Furthermore, the apparatus and method provided by this invention can further improve the quality of the epitaxial layer, enhancing its uniformity and the accuracy of doping concentration, thereby further improving the quality of the epitaxial wafer.

[0027] Of course, implementing any of the methods of this invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of 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 structural diagram of an epitaxial wafer fabrication apparatus according to an embodiment of the present invention.

[0030] Figure 2 for Figure 1 Partial structural diagram of the growth chamber, cooling chamber, wafer stage, and heating element.

[0031] Figure 3 for Figure 1 A partial structural diagram of the growth cavity.

[0032] Figure 4 for Figure 1 Structural diagram of the intermediate film stage.

[0033] Figure 5 This is a surface defect detection image of an epitaxial wafer in one embodiment of the present invention.

[0034] Label Explanation:

[0035] 10. Preparation apparatus; 11. Growth chamber; 111. Top; 112. Bottom; 113. Side; 12. Cooling chamber; 121. Top wall; 122. Bottom wall; 123. Side wall; 13. Vent hole; 14. Air inlet; 15. Heating element; 16. Stage; 161. Plate; 162. Protrusion; 163. Induction coil; 164. Central shaft; 17. Substrate; 18. Air inlet. Detailed Implementation

[0036] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0037] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0038] The technical solution of the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Please see Figures 1 to 4 As shown, the present invention provides an epitaxial wafer fabrication apparatus 10, including a growth chamber 11, a cooling chamber 12, a vent 13, an inlet 14, a heating element 15, a wafer stage 16, and an inlet 18. The growth chamber 11 includes a top 111, a bottom 112, and a side portion 113. The top 111 and bottom 112 are arranged opposite each other, and for example, coaxially. The size of the top 111 is, for example, larger than the size of the bottom 112. The side portion 113 is disposed between the top 111 and the bottom 112, with one end connected to the top 111 and the other end separated from the bottom 112 to facilitate the discharge of unreacted gas from the growth chamber 11. Furthermore, the material of the growth chamber 11 includes, for example, graphite, and a coating (not shown) is provided on the outer side of the growth chamber 11 to extend its lifespan. By providing the growth chamber 11, a site is provided for the growth of the epitaxial wafer.

[0040] Please see Figures 1 to 4 As shown, in one embodiment of the present invention, the air inlet 18 is connected to the top 111 to provide process gas to the growth chamber 11.

[0041] Please see Figures 1 to 4As shown, in one embodiment of the present invention, a cooling chamber 12 is arranged around the growth chamber 11, and the cooling chamber 12 and the growth chamber 11 are spaced apart. Specifically, in this embodiment, the cooling chamber 12 is arranged around the growth chamber 11 and the air inlet 18. The cooling chamber 12 includes, for example, a top wall 121, a bottom wall 122, and a side wall 123. The top wall 121 is spaced apart on one side of the top 111, the bottom wall 122 is arranged opposite to the top wall 121 and spaced apart on one side of the bottom 112, and the side wall 123 connects the top wall 121 and the bottom wall 122, and the side wall 123 and the side portion 113 are spaced apart.

[0042] Please see Figures 1 to 4 As shown, in one embodiment of the present invention, vent holes 13 are provided through the side portion 113. For example, there are multiple vent holes 13. In the axial direction of the growth chamber 11, the vent holes 13 are equidistantly arranged along the side portion 113, and in the direction perpendicular to the axial direction of the growth chamber 11, the vent holes 13 are arranged around the side portion 113. By providing vent holes 13, the growth chamber 11 and the cooling chamber 12 can be connected, facilitating the removal of particulate matter from the growth chamber 11 and its entry into the cooling chamber 12.

[0043] Please see Figures 1 to 4 As shown, in one embodiment of the present invention, an air inlet 14 is provided on the cooling chamber 12. Specifically, in this embodiment, there are, for example, two air inlets 14, one symmetrically arranged on the bottom wall 122 outside the growth chamber 11. By providing the air inlets 14, purge gas is provided to the cooling chamber 12.

[0044] Please see Figures 1 to 4 As shown, in one embodiment of the present invention, the heating element 15 is disposed outside the cooling cavity 12 to provide a heat source for the growth of the epitaxial wafer. Specifically, in this embodiment, the heating element 15 is, for example, a heating coil, which is disposed around the outside of the cooling cavity 12.

[0045] Please see Figures 1 to 4 As shown, in one embodiment of the present invention, the wafer stage 16 is disposed within the growth chamber 11. Specifically, in this embodiment, the wafer stage 16 is disposed, for example, on the bottom 112, and includes, for example, a plate 161, a protrusion 162, an induction coil 163, and a central shaft 164. One end of the central shaft 164 extends through the bottom 112 and the bottom wall 122 to the outside of the fabrication apparatus 10 and is electrically connected to the drive structure (not shown in the figure), while the other end extends into the growth chamber 11. The induction coil 163 is disposed on the side of the central shaft 164 away from the bottom 112, the plate 161 is located on the side of the induction coil 163 away from the central shaft 164, and the protrusion 162 is disposed around the side of the plate 161 away from the induction coil 163.

[0046] Please see Figures 1 to 4As shown, in one embodiment of the present invention, a substrate 17 is placed within the protrusion 162. The inner diameter of the protrusion 162 is, for example, equal to the diameter of the substrate 17, so that the substrate 17 can be secured within the protrusion 162, preventing the substrate 17 from detaching from the stage 16. By setting the substrate 17 and the stage 16, the driving structure sequentially drives the central shaft 164, the induction coil 163, the plate 161, the protrusion 162, and the substrate 17 to rotate, facilitating the uniform deposition of process gases on the substrate 17, thereby improving the quality of the epitaxial layer on the substrate 17.

[0047] Based on the above-described epitaxial wafer fabrication apparatus, the present invention also provides a method for fabricating epitaxial wafers, which can prepare various types of epitaxial wafers. In this embodiment, the fabrication method is described using the preparation of a silicon carbide homoepitaxial wafer as an example. Specifically, the fabrication method includes at least steps S11-S15.

[0048] Step S11: After placing the substrate on the wafer stage, draw the pressure in the growth chamber to the preset pressure.

[0049] Step S12: Etch the surface of the substrate.

[0050] Step S13: Form a buffer layer on the surface of the substrate.

[0051] Step S14: Purge gas is introduced between the cooling chamber and the growth chamber through the air inlet, process gas is introduced into the growth chamber, and the growth chamber is heated to the growth temperature. The process gas is deposited on the buffer layer to form an epitaxial layer.

[0052] Step S15: Cool the growth chamber to obtain an epitaxial wafer.

[0053] Please see Figures 1 to 4 As shown, in one embodiment of the present invention, in step S11, after the substrate 17 is placed inside the protrusion 162, the growth chamber 11 and the cooling chamber 12 are evacuated to a preset pressure to remove air and impurity gases from the fabrication apparatus, providing a clean environment for subsequent epitaxial growth. The substrate 17 is, for example, a single-crystal 4H-SiC substrate, and the preset pressure is, for example, less than or equal to 10 Pa.

[0054] Please see Figures 1 to 4As shown, in one embodiment of the present invention, after vacuuming, in step S12, the surface of the substrate 17 is etched in situ to remove the damaged layer and contaminants on the surface of the substrate 17, improving the flatness and cleanliness of the substrate 17 surface, facilitating the subsequent growth of the epitaxial layer. Specifically, in this embodiment, during the in-situ etching of the surface of the substrate 17, the growth chamber 11 and the cooling chamber 12 are heated to the etching temperature, and etching gas is introduced into the growth chamber 11 through the gas inlet 18 to remove the damaged layer and contaminants on the surface of the substrate 17. Specifically, the etching temperature is, for example, 1500℃-1600℃, the etching gas includes, for example, hydrogen and hydrogen chloride, the volume percentage of hydrogen chloride in the etching gas is, for example, 1%-5%, the etching time is, for example, 5min-60min, and the flow rate of the etching gas is, for example, 20slm-100slm. The addition of hydrogen chloride can enhance the etching effect and simultaneously inhibit premature growth of the epitaxial layer. Specifically, the addition of hydrogen chloride can suppress gas-phase pre-reaction and regulate the surface process. First, under high-temperature conditions, silicon sources readily undergo homogeneous nucleation in the gas phase, forming silicon clusters or particles. If these particles deposit on the substrate surface, they induce three-dimensional island growth, leading to increased surface roughness and defects. The addition of HCl rapidly reacts with active silicon species (Si, SiH) in the gas phase. x The reaction generates highly volatile chlorosilanes (such as SiCl4, SiH3Cl, etc.). This reaction significantly reduces the concentration of silicon atoms or small clusters in the gas phase and their polymerization tendency, thereby effectively inhibiting gas-phase nucleation and the resulting undesirable deposits. Secondly, on the substrate surface, HCl or its pyrolysis products (such as Cl radicals) exhibit competitive adsorption and selective etching. Chlorinated species occupy surface active sites, hindering the adsorption of silicon / carbon precursors. More importantly, HCl has mild etching activity for silicon atoms with weak surface bonding, in an amorphous state, or at high energy sites (such as rough island edges, dislocated atoms) (reaction formula: While etching silicon atoms already well-bonded in the SiC lattice is relatively slow, selective etching is more pronounced in the early stages of growth when the deposition rate is low. This selective etching can remove unstable silicon nuclei, islands, or surface irregularities formed in the early stages, leading to a decrease in net growth rate or even slight etch-back. Although initially exhibiting growth inhibition, this process substantially smooths the growth surface, eliminating heterogeneous nucleation sites and laying a crucial atomic-level smooth foundation for subsequent two-dimensional layered (Frank-van der Merwe mode) single-crystal epitaxial growth. Therefore, the introduction of HCl is a key process strategy for optimizing the initial nucleation of SiC epitaxy and obtaining high-quality, low-defect, smooth surfaces. Its flow rate needs to be precisely controlled to balance the inhibition effect with overall growth efficiency.

[0055] Please see Figures 1 to 4As shown, in one embodiment of the present invention, after etching the substrate 17, in step S13, a buffer gas is introduced into the growth chamber 11 through the gas inlet 18, and the growth chamber 11 is heated to a buffer temperature and maintained for a preset time to activate the surface of the substrate 17 and form a buffer layer on the surface of the substrate 17. The buffer gas may include, for example, hydrogen, and the buffer temperature is, for example, equal to the etching temperature. The preset time is, for example, 1 min to 20 min. The high-temperature hydrogen gas produces a gentle etching effect on the surface of the SiC substrate: preferentially etching high-energy regions such as surface defects and dislocation outcrops; promoting silicon atom surface migration and driving step edge regularization; forming a "hydrogen-terminated surface" with uniform step height, and suppressing 3D growth caused by secondary nucleation. By forming a buffer layer, firstly, it can repair near-surface damage layers of the substrate (such as submicron damage caused by mechanical polishing), block the extension of dislocations into the growth layer, and reduce the density of through dislocations. Secondly, the hydrogen-terminated surface lowers the adsorption energy barrier of the silicon carbide precursor, enhances the surface mobility of adsorbed atoms, and promotes two-dimensional layered growth (Frank-van der Merwe mode). Thirdly, as the initial stage of SiC epitaxial growth, the buffer layer establishes an atomically flat and stoichiometric template for high-quality epitaxy through surface cleaning, defect passivation, and lattice reconstruction. Fourthly, it can alleviate the stress between the substrate 17 and subsequent epitaxial layers, reduce defects caused by lattice mismatch and thermal mismatch, and thus improve the quality of the epitaxial wafer.

[0056] Please see Figures 1 to 4As shown, in one embodiment of the present invention, after the buffer layer is formed, in step S14, purge gas is introduced between the cooling chamber 12 and the growth chamber 11 through the air inlet 14. The purge gas diffuses to one side of the inner wall of the growth chamber 11 through the air vent 13. At the same time, process gas and carrier gas are introduced into the growth chamber 11 through the air inlet 18, and the growth chamber 11 is heated to the growth temperature. The process gas is deposited on the buffer layer to form an epitaxial layer. Since it takes time for the purge gas to diffuse from the cooling chamber 12 and the growth chamber 11 to the inner wall of the growth chamber 11, the flow rate of the purge gas between the cooling chamber 12 and the growth chamber 11 is greater than the flow rate of the purge gas on the inner wall of the growth chamber 11. Specifically, the flow rate of the purge gas between the cooling chamber 12 and the growth chamber 11 is, for example, 50 slm-100 slm, and the flow rate of the purge gas on the inner wall of the growth chamber 11 is, for example, 30 slm-60 slm. The growth temperature is, for example, 1550℃-1650℃, and the growth time is, for example, 20 min-60 min. The purge gas includes, for example, at least one of hydrogen and inert gas. Furthermore, within the growth chamber 11, the purge gas is distributed on both sides of the process gas, meaning the process gas is distributed at the center of the growth chamber 11. The purge gas is positioned close to the inner wall of the growth chamber 11. The process gas includes, for example, a growth source gas, a dopant source gas, and a carrier gas. The ratio of the growth source gas to the dopant source gas can be adjusted according to the required doping concentration and thickness of the epitaxial layer. Specifically, the flow rate of the growth source gas is, for example, 50 sccm-200 sccm, the flow rate of the dopant source gas is, for example, 5 slm-10 slm, and the flow rate of the carrier gas is, for example, 50 slm-150 slm. The growth source gas includes, for example, at least one of ethylene, propane, trichlorosilane (TCS), and silane. The dopant source gas includes, for example, an n-type dopant source or a p-type dopant source. The n-type dopant source includes, for example, nitrogen, and the p-type dopant source includes, for example, trimethylaluminum iodide (TMAI). The carrier gas includes, for example, hydrogen. Specifically, the process gas diffuses into the growth chamber 11 and undergoes a chemical reaction and adsorption on the surface of the substrate 17, forming a single-crystal homogeneous 4H-SiC epitaxial layer with a specific doping concentration, specific thickness, and higher quality on the surface of the substrate 17. At the same time, since the flow rate of the purge gas flowing between the cooling chamber 12 and the growth chamber 11 is greater than the flow rate of the purge gas flowing on one side of the inner wall of the growth chamber 11, based on the Venturi effect, particulate foreign matter near the inner wall of the growth chamber 11 can be carried out of the growth chamber 11 and into the space between the cooling chamber 12 and the growth chamber 11. This avoids the deposition of particulate foreign matter on the surface of the substrate 17, forming surface morphology defects such as falling object defects and triangular defects, as well as crystal structure defects such as stacking faults, thereby significantly improving the quality of the epitaxial layer.

[0057] Please see Figures 1 to 4As shown, in one embodiment of the present invention, after the epitaxial layer is formed, in step S15, the growth source gas, doping source gas and purge gas are stopped, heating is stopped, and carrier gas is continued to be introduced. After the preparation apparatus 10 is cooled to room temperature, the substrate 17 is taken out to obtain the epitaxial wafer.

[0058] Several specific embodiments are given below to illustrate the technical effects of this application.

[0059] Example 1

[0060] A 4H-SiC single crystal substrate was selected as the silicon carbide substrate. After cleaning, it was placed on the wafer stage, the growth chamber was closed, and the chamber was evacuated to 5 Pa. The temperature of the growth chamber was raised to 1550℃ by induction heating. A mixture of hydrogen and hydrogen chloride gas was introduced to perform in-situ etching on the substrate, with hydrogen chloride accounting for 2% of the volume. The total flow rate of the mixed gas was 50 slm, and the etching time was 10 min. After etching, the hydrogen chloride supply was stopped, but hydrogen gas was introduced again while maintaining the temperature to activate the substrate surface and form a buffer layer for 5 min. Subsequently, the high-temperature chemical vapor deposition stage was entered. The temperature of the reaction chamber was raised to 1600℃, and process gas was introduced into the growth chamber through the inlet. Hydrogen gas was introduced between the growth chamber and the cooling chamber through the inlet hole at a flow rate of 100 slm, and maintained for 30 min. Specifically, in the process gases, the growth sources are ethylene and TCS, with a flow rate of 50 sccm for ethylene and 100 sccm for TCS. The doping source is nitrogen, with a flow rate of 5 sccm. The carrier gas is hydrogen, with a flow rate of 100 slm. The hydrogen flow rate between the growth chamber and the cooling chamber is 80 slm, and the hydrogen flow rate along one side of the inner wall of the growth chamber is 50 slm. After growth is complete, the flow of the growth source and doping source is stopped, while the carrier gas continues to flow. After the fabrication apparatus cools to room temperature, the substrate is removed, yielding a silicon carbide homoepitaxial wafer.

[0061] Example 2

[0062] A 4H-SiC single crystal substrate was selected as the silicon carbide substrate. After cleaning, it was placed on the wafer stage, the growth chamber was closed, and the chamber was evacuated to 8 Pa. The temperature of the reaction chamber was raised to 1500℃ by induction heating, and a mixture of hydrogen and hydrogen chloride gas was introduced to perform in-situ etching on the substrate. The volume percentage of hydrogen chloride was 1%, the total flow rate of the mixed gas was 40 slm, and the etching time was 15 min. After etching, the hydrogen chloride supply was stopped, but hydrogen gas was continued to be introduced while maintaining the temperature to activate the substrate surface and form a buffer layer for 8 min. Subsequently, the high-temperature chemical vapor deposition stage was entered. The temperature of the reaction chamber was raised to 1550℃, and process gas was introduced into the growth chamber through the inlet. Hydrogen gas was introduced between the growth chamber and the cooling chamber through the inlet hole at a flow rate of 80 slm for 40 min. Specifically, in the process gases, the growth sources are propane and silane, with a propane flow rate of 40 sccm and a silane flow rate of 80 sccm. The dopant source is TMAI with a flow rate of 3 sccm. The carrier gas is hydrogen with a flow rate of 80 slm. The hydrogen flow rate between the growth chamber and the cooling chamber is 70 slm, and the hydrogen flow rate along one side of the inner wall of the growth chamber is 40 slm. After growth is complete, the flow of the growth source and dopant source is stopped, while the carrier gas continues to flow. After the fabrication apparatus cools to room temperature, the substrate is removed, yielding a silicon carbide homoepitaxial material.

[0063] Example 3

[0064] A 4H-SiC single crystal substrate was selected as the silicon carbide substrate. After cleaning, it was placed on the stage of the reaction chamber, the chamber was closed, and a vacuum of 3 Pa was applied. The temperature of the reaction chamber was raised to 1600℃ by induction heating. A mixture of hydrogen and hydrogen chloride gas was introduced to perform in-situ etching on the substrate, with hydrogen chloride accounting for 5% of the volume. The total flow rate of the mixed gas was 60 slm, and the etching time was 8 min. After etching, the hydrogen chloride supply was stopped, but hydrogen gas was continued to be introduced while maintaining the temperature to activate the substrate surface and form a buffer layer for 3 min. Subsequently, the high-temperature chemical vapor deposition stage was entered. The temperature of the reaction chamber was raised to 1650℃, and process gas was introduced into the growth chamber through the inlet. Hydrogen gas was introduced between the growth chamber and the cooling chamber through the inlet hole at a flow rate of 120 slm, and maintained for 25 min. Specifically, in the process gases, the growth sources are ethylene and silane, with a flow rate of 60 sccm for ethylene and 120 sccm for silane. The dopant source is nitrogen with a flow rate of 8 sccm, and the carrier gas is hydrogen with a flow rate of 120 slm. The hydrogen flow rate between the growth chamber and the cooling chamber is 90 slm, and the hydrogen flow rate along one side of the inner wall of the growth chamber is 60 slm. After growth is complete, the flow of the growth source and dopant source is stopped, but hydrogen is continued. After the fabrication apparatus cools to room temperature, the substrate is removed, yielding a silicon carbide homoepitaxial material.

[0065] In one embodiment of the present invention, the silicon carbide homoepitaxial wafer prepared in Example 1 above was subjected to surface morphology and defect observation, for example, using Oncon Vision's E3500 SiC defect detection equipment. The results are as follows: Figure 5 As shown, for example, crystal structure defects inside the epitaxial layer are observed using transmission electron microscopy; the doping concentration distribution of the epitaxial layer is analyzed using secondary ion mass spectrometry; and the thickness deviation of the epitaxial layer is tested using elliptic polarization spectroscopy. The results indicate that... Figure 5 It can be seen that the surface of the epitaxial wafer is flat, without obvious surface morphology defects such as falling objects and triangular defects, and the density of crystal structure defects such as stacking faults is also significantly reduced. In addition, the doping concentration of the epitaxial layer is uniform and the thickness deviation is small. This shows that the quality of the epitaxial wafer can be improved by the preparation device and preparation method provided by the present invention.

[0066] In summary, this invention provides an apparatus and method for preparing epitaxial wafers. By optimizing the apparatus and method, particulate foreign matter within the growth chamber can be removed, preventing its deposition on the substrate surface and thus avoiding surface morphology defects such as falling particles or triangular defects, as well as crystal structure defects such as stacking faults. This significantly improves the quality of the epitaxial wafer. Furthermore, the apparatus and method provided by this invention, by forming a buffer layer between the epitaxial layer and the substrate, can further improve the quality of both the epitaxial layer and the epitaxial wafer.

[0067] The embodiments of the present invention disclosed above are merely illustrative of the invention. The embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An apparatus for preparing an epitaxial wafer, characterized in that, At least including: The growth chamber includes a top and a bottom disposed opposite to each other, and a side portion disposed between the top and the bottom; A cooling chamber is arranged around the growth chamber, and the cooling chamber and the growth chamber are spaced apart. Multiple ventilation holes are spaced apart and arranged through the side portion; An air inlet is provided on the cooling chamber; The heating element is disposed outside the cooling chamber; as well as A slide stage is disposed within the growth chamber.

2. The preparation apparatus according to claim 1, characterized in that, The cooling chamber includes a top wall and a bottom wall that are disposed opposite to each other, the top wall being spaced apart from the top and the bottom wall being spaced apart from the bottom.

3. The preparation apparatus according to claim 2, characterized in that, The cooling chamber also includes a sidewall, which connects the top wall and the bottom wall, and the sidewall and the side portion are spaced apart.

4. The preparation apparatus according to claim 3, characterized in that, The air inlet is located on the bottom wall.

5. A method for preparing an epitaxial wafer, characterized in that, Using the preparation apparatus according to any one of claims 1-4, the process includes at least the following steps: After placing the substrate on the stage, the pressure inside the growth chamber is reduced to the preset pressure; Etch the surface of the substrate; A buffer layer is formed on the surface of the substrate; Purge gas is introduced between the cooling chamber and the growth chamber through the air inlet. The purge gas diffuses to one side of the inner wall of the growth chamber through the vent. Simultaneously, process gas is introduced into the growth chamber, heating it to the growth temperature. The process gas is deposited on the buffer layer to form an epitaxial layer. The growth chamber is cooled to obtain an epitaxial wafer.

6. The preparation method according to claim 5, characterized in that, The flow rate of the purge gas between the cooling chamber and the growth chamber is greater than the flow rate of the purge gas on the inner wall side of the growth chamber.

7. The preparation method according to claim 5, characterized in that, Inside the growth chamber, the purging gas is distributed on both sides of the process gas.

8. The preparation method according to claim 5, characterized in that, When etching the surface of the substrate, the growth chamber is heated to the etching temperature and etching gas is introduced into the growth chamber.

9. The preparation method according to claim 8, characterized in that, The etching temperature is 1500℃-1600℃, and the etching gas includes hydrogen and hydrogen chloride.

10. The preparation method according to claim 9, characterized in that, The hydrogen chloride in the etching gas accounts for 1%-5% of the total volume.

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