Silicon carbide thick film and epitaxial growth method and application thereof

Abstract

The invention belongs to the technical field of semiconductor manufacturing, and discloses a silicon carbide thick film and an epitaxial growth method and application thereof, and the epitaxial growth method of the silicon carbide thick film comprises the following steps: growing on a first surface of a substrate to a first thickness at a first growth rate; performing first in-situ annealing; continuously growing to a target thickness at a second growth rate; and performing second in-situ annealing. In the epitaxial growth of the target silicon carbide thick film, through the step-by-step process sequence of two times of epitaxial growth and two times of in-situ annealing and the whole-process in-situ process design, intrinsic stress and thermal stress accumulated in the growth process of the silicon carbide thick film are effectively released, and the warping problem is fundamentally inhibited; meanwhile, annihilation and recombination of defects such as dislocation are promoted, and the crystal quality of the epitaxial layer is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, and specifically relates to a silicon carbide thick film and its epitaxial growth method and application. Background Technology

[0002] Silicon carbide (SiC) power devices, with their superior characteristics such as high breakdown electric field, high thermal conductivity, and fast switching speed, have become core components in fields such as new energy vehicles, high-voltage power transmission, and rail transportation. The blocking voltage capability of devices like MOSFETs and diodes directly depends on the thickness and doping concentration of the epitaxial layer. As power electronic equipment upgrades towards higher voltage and higher power, the market demand for 10,000-volt-level high-voltage devices is becoming increasingly urgent. This requires the SiC epitaxial layer thickness to reach at least 100 μm to meet the insulation and withstand voltage requirements of devices in high-voltage scenarios. At the same time, to improve production efficiency and reduce unit device costs, the semiconductor industry is accelerating its transformation to 8-inch large-size wafer processes. 8-inch SiC thick-film epitaxial technology has become one of the core bottlenecks in achieving large-scale mass production of high-voltage devices.

[0003] However, growing thick SiC epitaxial layers exceeding 100 μm on 8-inch wafers presents formidable technical challenges. On one hand, an unavoidable difference in lattice constants exists between the SiC substrate and the epitaxial layer. This lattice mismatch generates initial stress at the interface, which accumulates and cannot be fully released through lattice relaxation as the epitaxial layer thickness increases. On the other hand, epitaxial growth requires temperatures above 1500°C, and the inherent difference in thermal expansion coefficients between the SiC substrate and the epitaxial layer leads to different degrees of shrinkage during subsequent cooling, further generating significant thermal stress. The superposition of these two stresses creates enormous internal stress within the wafer, easily causing severe warping of the 8-inch wafer and even fatal defects such as cracks and peeling in the epitaxial layer.

[0004] Severe wafer warpage can directly disrupt subsequent precision processing steps such as photolithography and etching. Photolithography demands extremely high wafer flatness; warped wafers cause uneven photoresist coating and significant deviations in pattern transfer accuracy, ultimately leading to device failure. Meanwhile, cracking of the epitaxial layer directly results in product scrap, drastically reducing production yield and significantly increasing raw material and manufacturing costs, severely hindering the industrialization of 10,000-volt 8-inch SiC high-voltage devices. Currently, the industry lacks a mature and effective solution to balance the contradictions between thick-film growth, large-size compatibility, and stress control. Effectively suppressing stress accumulation during thick-film epitaxy and preventing wafer warpage and epitaxial layer cracking has become a key technical challenge that must be overcome to achieve mass production of 8-inch SiC high-voltage power devices. Summary of the Invention

[0005] The present invention aims to improve at least one technical problem in the prior art.

[0006] The first aspect of this invention provides a method for epitaxial growth of a silicon carbide thick film, comprising the following steps: Step S1: Introduce a first reaction source at a first temperature and grow to a first thickness on the first surface of the substrate at a first growth rate; Step S2: Stop the flow of the first reaction source, introduce inert gas, and perform the first in-situ annealing under the condition of cooling to the second temperature; Step S3: Under the condition of heating to the first temperature, stop the inert gas supply, and introduce the first reaction source again to continue growing to the target thickness at the second growth rate; Step S4: Stop the flow of the first reaction source, introduce the inert gas, and perform the second in-situ annealing under the condition of cooling to the second temperature; Wherein, the first temperature is 1580℃-1650℃, and the second temperature is 1500℃-1550℃; Wherein, the first growth rate is 30 μm / h, and the second growth rate is 60 μm / h; The first in-situ annealing time is 15 min-30 min, and the second in-situ annealing time is 5 min-10 min; The first thickness is 40μm-50μm, and the target thickness is not less than 100μm.

[0007] The silicon carbide thick film epitaxial growth method provided in this application reduces stress accumulation during the thick film growth process from the root through a synergistic design of staged growth and in-situ annealing. The first temperature is set at 1580℃-1650℃, which is the optimal temperature range for silicon carbide epitaxial growth, ensuring the crystal quality and growth stability of the epitaxial layer. The first growth rate is controlled at 30μm / h. The lower growth rate ensures that the first base epitaxial layer with a thickness of 40μm-50μm has a smooth surface morphology and low defect density, laying a good foundation for subsequent growth. After growth, the first reaction source is stopped and an inert gas is introduced, which avoids interference from residual reaction gas to subsequent processes and maintains stable pressure in the reaction chamber. The second temperature, 1500℃-1550℃, is slightly lower than the first temperature and is within the atomically active range. Under these conditions, a first in-situ annealing of 15min-30min provides sufficient energy for lattice atoms to rearrange, releasing the intrinsic stress accumulated in the first stage of growth, and promoting the annihilation and recombination of defects such as dislocations, thus optimizing the surface state of the base epitaxial layer. The temperature is then raised to the first temperature, and the first reaction source is introduced again. Growth continues at a second growth rate of 60 μm / h. This higher growth rate improves process efficiency while ensuring quality, ultimately achieving a total film thickness of at least 100 μm, thus balancing low stress and high efficiency. Finally, a second in-situ annealing is performed to provide final stress relaxation and structural stabilization for the silicon carbide thick film, ensuring a low-stress state and good structural integrity after growth. This second in-situ annealing is a short-time high-temperature annealing process that releases the final stress in the overall silicon carbide thick film formed by the two epitaxial growths, further repairing any minor defects that may remain from the growth process and improving the overall crystal quality of the silicon carbide thick film.

[0008] Preferably, the substrate is made of 4H-SiC and has a thickness of 350 μm.

[0009] 4H-SiC possesses excellent crystal structure stability, high thermal conductivity, and good electrical properties, making it an ideal substrate material for fabricating high-performance silicon carbide thick films. It can match the process requirements of thick film epitaxial growth and ensure the performance of the final device. Setting the substrate thickness to 350 μm ensures sufficient structural strength and stability, reducing initial warpage during high-temperature epitaxy and subsequent processes. This provides a stable support foundation for uniform thick film growth and avoids stress unevenness in the epitaxial layer caused by insufficient substrate rigidity.

[0010] Preferably, step S0 is included before step S1, and step S0 includes: A second reaction source is introduced under the first temperature condition, and the substrate is grown to a second thickness on the second surface. The second side is the side opposite to the first side; the second thickness is the same as the first thickness.

[0011] In this application, step S0 is designed to further optimize the flatness and structural stability of the substrate through a symmetrical design of double-sided substrate growth. The second side of the substrate is opposite to the first side. Under the first temperature condition, a second reaction source is introduced to grow the substrate to a second thickness that is the same as the first thickness in the subsequent design. This can effectively increase the overall thickness of the substrate and reduce the initial warpage.

[0012] Preferably, the second reaction source is doped with trimethylaluminum, and the doping concentration of trimethylaluminum is 4 × 10⁻⁶. 14 cm -3 - 8×10 14 cm -3 .

[0013] In this application, trimethylaluminum adjusts the warpage trend of the substrate through reverse doping, providing warpage correction support for the subsequent growth of the first epitaxial layer, further reducing thick film warpage caused by single-sided growth, and ensuring the flatness and electrical performance consistency of the entire epitaxial structure.

[0014] Preferably, before step S1, the first surface undergoes a surface treatment, which includes the following steps: Hydrogen etching was performed at 1350℃-1450℃ for 5-10 minutes. The hydrogen etching pressure is 80mbar-120mbar.

[0015] The hydrogen etching of the first surface of the substrate in this application effectively removes the oxide layer, organic impurities, and minute defects, achieving an atomically clean surface. This surface treatment significantly improves the interfacial adhesion between the epitaxial layer and the substrate, reduces interfacial defects, and provides a smooth and clean growth interface for the subsequent first-stage epitaxial growth, ensuring the crystal quality and growth uniformity of the epitaxial layer.

[0016] Preferably, the C / Si stoichiometric ratio in the first reaction source is 1.05-1.1.

[0017] This application controls the C / Si stoichiometry of the first reaction source within the range of 1.05-1.1. This ratio, slightly higher than the stoichiometry, is a key parameter design for suppressing the generation of polymorphic defects in 3C-SiC. During silicon carbide epitaxial growth, precise control of the C / Si ratio directly affects the integrity of the crystal structure. A slightly higher C / Si ratio can avoid the precipitation of 3C-SiC polymorphic phases due to excessive silicon content, ensuring that the epitaxial layer always grows with the target crystal structure, improving the crystal uniformity and overall quality of the silicon carbide thick film, and avoiding the adverse effects of polymorphic defects on the electrical properties and structural stability of the silicon carbide thick film.

[0018] Preferably, the carbon source in the first reaction source is ethylene, and the silicon source is trichlorosilane.

[0019] Preferably, the first reaction source is doped with a first dopant source, which is ammonia or nitrogen, and the doping concentration of the first dopant source is 4 × 10⁻⁶. 14 cm -3 - 8×10 14 cm -3 .

[0020] Ammonia or nitrogen can be used as the first doping source. Both can introduce nitrogen impurities into the epitaxial layer, thereby achieving the required conductivity type control and meeting the electrical performance requirements of subsequent device applications.

[0021] Preferably, in step S4, after the second in-situ annealing is completed, the temperature is lowered to a third temperature at a first cooling rate and held at that temperature, and then the temperature is further lowered to a fourth temperature at the first cooling rate and allowed to cool naturally to room temperature. The third temperature is 1000℃, and the fourth temperature does not exceed 600℃; The heat preservation time is 10-15 minutes; The first cooling rate is 30℃ / min.

[0022] This application further employs a slow cooling design with a first cooling rate of 30℃ / min, which reduces the thermal stress generated by the temperature gradient during the cooling process of the silicon carbide thick film, thereby reducing warping or cracking caused by thermal stress during cooling. Holding at a third temperature of 1000℃ for 10-15 minutes can specifically relax the thermal stress in the middle temperature range, making the internal temperature distribution of the silicon carbide thick film more uniform. Continuing to cool to a fifth temperature not exceeding 600℃ and then allowing it to cool naturally to room temperature can avoid the impact of sudden temperature changes on the silicon carbide thick film structure during subsequent cooling processes, further ensuring the low stress, high integrity, and structural stability of the silicon carbide thick film.

[0023] Furthermore, after epitaxial growth is completed, the silicon carbide film grown on the second surface is subjected to chemical mechanical polishing to remove 40μm-50μm.

[0024] A second aspect of the present invention provides a silicon carbide thick film, which is obtained according to the epitaxial growth method described above.

[0025] The third aspect of the present invention provides the application of the above-described silicon carbide thick film in the fabrication of 10,000-volt high-voltage devices.

[0026] The beneficial effects of this invention are as follows: In the epitaxial growth of target silicon carbide thick films, this invention effectively releases the intrinsic and thermal stress accumulated during the growth process through a step-by-step process sequence of two epitaxial growths and two in-situ annealings, along with a fully in-situ process design. This fundamentally suppresses warpage and promotes the annihilation and recombination of defects such as dislocations, significantly improving the crystal quality of the epitaxial layer. The first in-situ annealing optimizes the surface state of the first epitaxial growth, providing a stable and flat growth foundation for the second epitaxial growth and ensuring a high-quality interlayer interface. The entire process does not require removing the wafer, and the key in-situ annealing steps utilize an inert gas atmosphere, completely avoiding interface contamination and oxidation risks. This also ensures the stability of the surface morphology and process repeatability, ultimately achieving low-stress, high-purity, and high-consistency fabrication of silicon carbide thick films, providing reliable support for the large-scale mass production of high-voltage power devices. Attached Figure Description

[0027] Figure 1 An optical photograph of the surface of a silicon carbide thick film obtained by the epitaxial growth method of Example 1; Figure 2 This is an optical photograph of the surface of a silicon carbide film obtained by the epitaxial growth method of Comparative Example 6. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the description of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0029] Example 1 An epitaxial growth method for silicon carbide thick films is disclosed. The substrate used in this method is a 350 μm thick 4H-SiC substrate, comprising a first side and a second side (facing away from each other). The substrate undergoes standard RCA (Reverse Calibration Process) cleaning, ultrapure water rinsing, and nitrogen drying. The epitaxial growth method includes the following steps: Using the second (back) side as the epitaxial surface, the substrate was placed in a CVD reaction chamber, and trichlorosilane and ethylene (simultaneously doped with trimethylaluminum at a doping concentration of 5 × 10⁻⁶) were introduced at 1620°C. 14cm -3 The substrate is epitaxially grown to 50 μm on the second side of the substrate, cooled to 900°C, and then removed for cooling. Using the first side (front side) as the epitaxial surface, the substrate was placed in the CVD reaction chamber, hydrogen gas (purity 99.99999%) was introduced, and hydrogen etching was performed at 1450℃ for 5 minutes at a pressure of 120 mbar. Under conditions of heating to 1620℃, trichlorosilane and ethylene (with a C / Si stoichiometric ratio of 1.05) are introduced; nitrogen is also introduced, with a nitrogen doping concentration of 4 × 10⁻⁶. 14 cm -3 ), grown to 50 μm on the first surface of the substrate at a growth rate of 30 μm / h; Stop the flow of trichlorosilane, ethylene, nitrogen and hydrogen, introduce argon, and perform the first in-situ annealing for 15 min at a temperature of 1520℃. When the temperature is raised to 1620℃, the argon gas supply is stopped, and hydrogen, trichlorosilane, and ethylene (with a C / Si stoichiometric ratio of 1.05) are introduced again; nitrogen is also introduced simultaneously at a concentration of 4 × 10⁻⁶. 14 cm -3 It continued to grow to 100 μm at a growth rate of 60 μm / h; Stop the flow of trichlorosilane, ethylene, nitrogen and hydrogen, introduce argon, and perform a second in-situ annealing at 1520℃ for 5 min. Then, cool down to 1000℃ at a rate of 30℃ / min and hold for 10 min. Then, continue cooling down to 600℃ at a rate of 30℃ / min and finally allow it to cool naturally to room temperature to complete the epitaxial growth of silicon carbide thick film.

[0030] Optical photographs of the silicon carbide thick film surface obtained by the epitaxial growth method of Example 1 are shown below. Figure 1 As shown.

[0031] Comparative Example 1 An epitaxial growth method for silicon carbide films, wherein the substrate used in the epitaxial growth method is a 350 μm thick 4H-SiC substrate, the substrate includes a first side and a second side (the first side and the second side are opposite to each other), the substrate is cleaned by standard RCA (Semiconductor Industry Standard Wet Cleaning Process), rinsed with ultrapure water, and dried with nitrogen; the epitaxial growth method includes the following steps: Using the second (back) side as the epitaxial surface, the substrate was placed in a CVD reaction chamber, and trichlorosilane and ethylene (simultaneously doped with trimethylaluminum at a doping concentration of 5 × 10⁻⁶) were introduced at 1620°C. 14 cm -3 The substrate is epitaxially grown to 50 μm on the second side of the substrate, cooled to 900°C, and then removed for cooling. Using the first side (front side) as the epitaxial surface, the substrate was placed in the CVD reaction chamber, hydrogen gas (purity 99.99999%) was introduced, and hydrogen etching was performed at 1450℃ for 5 minutes at a pressure of 120 mbar. Under conditions of heating to 1620℃, trichlorosilane and ethylene (with a C / Si stoichiometric ratio of 1.05) are introduced; nitrogen is also introduced, with a nitrogen doping concentration of 4 × 10⁻⁶. 14 cm -3 The silicon carbide film was grown to 100 μm on the first side of the substrate at a growth rate of 60 μm / h and then naturally cooled to room temperature to complete the epitaxial growth of the silicon carbide film.

[0032] Comparative Example 2 An epitaxial growth method for silicon carbide films, wherein the substrate used in the epitaxial growth method is a 350 μm thick 4H-SiC substrate, the substrate includes a first side and a second side (the first side and the second side are opposite to each other), the substrate is cleaned by standard RCA (Semiconductor Industry Standard Wet Cleaning Process), rinsed with ultrapure water, and dried with nitrogen; the epitaxial growth method includes the following steps: Using the second (back) side as the epitaxial surface, the substrate was placed in a CVD reaction chamber, and trichlorosilane and ethylene (simultaneously doped with trimethylaluminum at a doping concentration of 5 × 10⁻⁶) were introduced at 1620°C. 14 cm -3 The substrate is epitaxially grown to 50 μm on the second side of the substrate, cooled to 900°C, and then removed for cooling. Using the first side (front side) as the epitaxial surface, the substrate was placed in the CVD reaction chamber, hydrogen gas (purity 99.99999%) was introduced, and hydrogen etching was performed at 1450℃ for 5 minutes at a pressure of 120 mbar. Under conditions of heating to 1620℃, trichlorosilane and ethylene (with a C / Si stoichiometric ratio of 1.05) are introduced; nitrogen is also introduced, with a nitrogen doping concentration of 4 × 10⁻⁶. 14 cm -3 ), grown to 50 μm on the first surface of the substrate at a growth rate of 30 μm / h; Maintaining the temperature at 1620℃, the material continued to grow to 100μm at a growth rate of 60μm / h. Stop the flow of trichlorosilane, ethylene, nitrogen and hydrogen, introduce argon, and perform in-situ annealing at 1520℃ for 5 min. Then, cool down to 1000℃ at a rate of 30℃ / min and hold for 10 min. Continue cooling down to 600℃ at a rate of 30℃ / min, and finally allow to cool naturally to room temperature to complete the epitaxial growth of the silicon carbide film.

[0033] Comparative Example 3 An epitaxial growth method for silicon carbide films, wherein the substrate used in the epitaxial growth method is a 350 μm thick 4H-SiC substrate, the substrate includes a first side and a second side (the first side and the second side are opposite to each other), the substrate is cleaned by standard RCA (Semiconductor Industry Standard Wet Cleaning Process), rinsed with ultrapure water, and dried with nitrogen; the epitaxial growth method includes the following steps: Using the second (back) side as the epitaxial surface, the substrate was placed in a CVD reaction chamber, and trichlorosilane and ethylene (simultaneously doped with trimethylaluminum at a doping concentration of 5 × 10⁻⁶) were introduced at 1620°C. 14 cm -3 The substrate is epitaxially grown to 50 μm on the second side of the substrate, cooled to 900°C, and then removed for cooling. Using the first side (front side) as the epitaxial surface, the substrate was placed in the CVD reaction chamber, hydrogen gas (purity 99.99999%) was introduced, and hydrogen etching was performed at 1450℃ for 5 minutes at a pressure of 120 mbar. Under conditions of heating to 1620℃, trichlorosilane and ethylene (with a C / Si stoichiometric ratio of 1.05) are introduced; nitrogen is also introduced, with a nitrogen doping concentration of 4 × 10⁻⁶. 14 cm -3 ), grown to 50 μm on the first surface of the substrate at a growth rate of 30 μm / h; Stop the flow of trichlorosilane, ethylene, nitrogen and hydrogen, introduce argon, and perform the first in-situ annealing for 15 min at a temperature of 1520℃. When the temperature is raised to 1620℃, the argon gas supply is stopped, and hydrogen, trichlorosilane, and ethylene (with a C / Si stoichiometric ratio of 1.05) are introduced again; nitrogen is also introduced simultaneously at a concentration of 4 × 10⁻⁶. 14 cm -3 The silicon carbide thick film was grown at a growth rate of 60 μm / h to 100 μm and then naturally cooled to room temperature to complete the epitaxial growth of the silicon carbide thick film.

[0034] Comparative Example 4 An epitaxial growth method for silicon carbide films, wherein the substrate used in the epitaxial growth method is a 350 μm thick 4H-SiC substrate, the substrate includes a first side and a second side (the first side and the second side are opposite to each other), the substrate is cleaned by standard RCA (Semiconductor Industry Standard Wet Cleaning Process), rinsed with ultrapure water, and dried with nitrogen; the epitaxial growth method includes the following steps: Using the second (back) side as the epitaxial surface, the substrate was placed in a CVD reaction chamber, and trichlorosilane and ethylene (simultaneously doped with trimethylaluminum at a doping concentration of 5 × 10⁻⁶) were introduced at 1620°C. 14 cm -3The substrate is epitaxially grown to 50 μm on the second side of the substrate, cooled to 900°C, and then removed for cooling. Using the first side (front side) as the epitaxial surface, the substrate was placed in the CVD reaction chamber, hydrogen gas (purity 99.99999%) was introduced, and hydrogen etching was performed at 1450℃ for 5 minutes at a pressure of 120 mbar. Under conditions of heating to 1620℃, trichlorosilane and ethylene (with a C / Si stoichiometric ratio of 1.05) are introduced; nitrogen is also introduced, with a nitrogen doping concentration of 4 × 10⁻⁶. 14 cm -3 ), grown to 50 μm on the first surface of the substrate at a growth rate of 30 μm / h; Stop the flow of trichlorosilane, ethylene, nitrogen and hydrogen, introduce argon, and perform the first in-situ annealing for 15 minutes at a temperature of 1300℃. When the temperature is raised to 1620℃, the argon gas supply is stopped, and hydrogen, trichlorosilane, and ethylene (with a C / Si stoichiometric ratio of 1.05) are introduced again; nitrogen is also introduced simultaneously at a concentration of 4 × 10⁻⁶. 14 cm -3 It continued to grow to 100 μm at a growth rate of 60 μm / h; Stop the flow of trichlorosilane, ethylene, nitrogen and hydrogen, introduce argon, and perform a second in-situ annealing at 1520℃ for 5 min. Then, cool down to 1000℃ at a rate of 30℃ / min and hold for 10 min. Then, continue cooling down to 600℃ at a rate of 30℃ / min and finally allow it to cool naturally to room temperature to complete the epitaxial growth of the silicon carbide film.

[0035] Comparative Example 5 An epitaxial growth method for silicon carbide films, wherein the substrate used in the epitaxial growth method is a 350 μm thick 4H-SiC substrate, the substrate includes a first side and a second side (the first side and the second side are opposite to each other), the substrate is cleaned by standard RCA (Semiconductor Industry Standard Wet Cleaning Process), rinsed with ultrapure water, and dried with nitrogen; the epitaxial growth method includes the following steps: Using the second (back) side as the epitaxial surface, the substrate was placed in a CVD reaction chamber, and trichlorosilane and ethylene (simultaneously doped with trimethylaluminum at a doping concentration of 5 × 10⁻⁶) were introduced at 1620°C. 14 cm -3 The substrate is epitaxially grown to 50 μm on the second side of the substrate, cooled to 900°C, and then removed for cooling. Using the first side (front side) as the epitaxial surface, the substrate was placed in the CVD reaction chamber, hydrogen gas (purity 99.99999%) was introduced, and hydrogen etching was performed at 1450℃ for 5 minutes at a pressure of 120 mbar. Under conditions of heating to 1620℃, trichlorosilane and ethylene (with a C / Si stoichiometric ratio of 1.05) are introduced; nitrogen is also introduced, with a nitrogen doping concentration of 4 × 10⁻⁶. 14 cm -3 ), grown to 50 μm on the first surface of the substrate at a growth rate of 30 μm / h; Continue at 1620℃, stop the flow of trichlorosilane, ethylene, nitrogen and hydrogen, and introduce argon gas, and keep warm for 15 minutes; Maintaining the temperature at 1620℃, stop the argon gas supply and then introduce hydrogen, trichlorosilane, and ethylene (with a C / Si stoichiometric ratio of 1.05); simultaneously, dope with nitrogen at a concentration of 4 × 10⁻⁶. 14 cm -3 It continued to grow to 100 μm at a growth rate of 60 μm / h; Stop the flow of trichlorosilane, ethylene, nitrogen and hydrogen, introduce argon, and perform in-situ annealing at 1520℃ for 5 min. Then, cool down to 1000℃ at a rate of 30℃ / min and hold for 10 min. Continue cooling down to 600℃ at a rate of 30℃ / min, and finally allow to cool naturally to room temperature to complete the epitaxial growth of the silicon carbide film.

[0036] Comparative Example 6 An epitaxial growth method for silicon carbide films differs from Example 1 in that, after epitaxial growth begins on the first side of the substrate, the sample is removed midway through the process. Otherwise, it is the same as Example 1.

[0037] Optical photographs of the silicon carbide film surface obtained by the epitaxial growth method in Comparative Example 6 are shown below. Figure 2 As shown.

[0038] refer to Figure 1 and Figure 2 As can be seen, the surface of the silicon carbide film obtained in Comparative Example 6 was severely contaminated due to the removal of the sample during epitaxial growth.

[0039] Performance testing The products obtained by the epitaxial growth methods of Example 1 and Comparative Examples 1-5 were tested for local maximum flatness, curvature, and warpage, with the test methods referring to GB / T 12964-2018. The test results are shown in Table 1.

[0040] Table 1 Referring to Table 1, a comparison of the test data from Example 1 and the comparative examples shows that the silicon carbide thick film epitaxial growth method of the present invention has significant advantages in improving the surface condition and stress control of thick films: The local maximum flatness, curvature, and warpage of Example 1 are all significantly better than those of Comparative Example 1. Comparative Example 1 uses a single high-speed growth and natural cooling epitaxial growth method without step-by-step epitaxy and in-situ annealing. Its curvature and warpage are much higher than those of Example 1. This shows that the step-by-step strategy of two epitaxys and two in-situ annealings can effectively suppress stress accumulation in thick film growth and greatly improve the curvature and warpage of the wafer. Comparing Example 1 and Comparative Example 2, although Comparative Example 2 adopted stepwise growth, it did not set intermediate in-situ annealing between the two growths. After direct continuous growth, only one annealing was performed. Its curvature and warpage were still higher than those of Example 1. This confirms the key role of intermediate in-situ annealing in releasing the growth stress of the first stage and optimizing the surface condition. The lack of this step will cause the stress to be unable to relax in time, thus affecting the final morphological indicators. Comparative Example 3 did not use controlled cooling after step-by-step and intermediate annealing, but was naturally cooled to room temperature. Its warpage was significantly higher than that of Example 1. This shows that the controlled cooling design of slow cooling and intermediate temperature holding can further alleviate the thermal stress during the cooling process, which is an important step in reducing warpage. Comparative Example 4 reduced the intermediate in-situ annealing temperature to 1300℃ (deviating from the atomically active range), while Comparative Example 5 did not reduce the temperature during intermediate annealing (maintaining the growth temperature). The warpage of both examples was higher than that of Example 1. This indicates that intermediate annealing needs to be controlled within a temperature range that is "slightly lower than the growth temperature but within the atomically active range" in order to effectively promote lattice relaxation and defect repair. Temperatures that are too high or too low will weaken the stress release effect of annealing.

[0041] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature.

[0042] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for epitaxial growth of a silicon carbide thick film, characterized by, The method comprises the following steps: S1: growing to a first thickness on a first surface of a substrate at a first growth rate under a condition of a first temperature by introducing a first reaction source; S2: stopping the introduction of the first reaction source, introducing an inert gas, and performing a first in-situ annealing under a condition of a second temperature by reducing temperature; S3: continuing to grow to a target thickness at a second growth rate by introducing the first reaction source again under a condition of the first temperature by stopping the introduction of the inert gas and increasing temperature; S4: stopping the introduction of the first reaction source, introducing the inert gas, and performing a second in-situ annealing under a condition of the second temperature by reducing temperature; The first temperature is 1580-1650℃, and the second temperature is 1500-1550℃; The first growth rate is 30μm / h, and the second growth rate is 60μm / h; The first in-situ annealing time is 15-30min, and the second in-situ annealing time is 5-10min; The first thickness is 40-50μm, and the target thickness is not less than 100μm.

2. The method for epitaxial growth of a silicon carbide thick film according to claim 1, wherein The substrate is made of 4H-SiC, and the thickness of the substrate is 350μm.

3. The method for epitaxial growth of silicon carbide thick films according to claim 2, wherein Before the step S1, the method further comprises a step S0, which comprises: introducing a second reaction source under a condition of the first temperature to grow to a second thickness on a second surface of the substrate; The second surface is opposite to the first surface, and the second thickness is the same as the first thickness.

4. The method for epitaxial growth of silicon carbide thick films according to claim 3, wherein The second reaction source is doped with trimethylaluminum, and the doping concentration of the trimethylaluminum is 4x10 14 cm -3 - 8x10 14 cm -3 .

5. The method for epitaxial growth of silicon carbide thick films according to claim 1, wherein Before the step S1, the first surface is further subjected to surface treatment, which comprises the following steps: performing hydrogen etching at 1350-1450℃ for 5-10min; The pressure of the hydrogen etching is 80-120mbar.

6. The epitaxial growth method for silicon carbide thick films according to claim 1, characterized in that, The stoichiometric ratio of C / Si in the first reaction source is 1.05-1.

1.

7. The epitaxial growth method for silicon carbide thick films according to claim 1, characterized in that, The first reaction source is doped with a first doping source, the first doping source is ammonia or nitrogen, and a doping concentration of the first doping source is 4x10 14 cm -3 -8x10 14 cm -3 .

8. The method of claim 1, wherein the silicon carbide thick film is grown by an epitaxial process. After the second in-situ annealing in the step S4 is completed, the temperature is reduced to a third temperature at a first reducing rate, and then the temperature is continuously reduced to a fourth temperature at the first reducing rate, and the temperature is naturally cooled to room temperature; The third temperature is 1000℃, and the fourth temperature is not more than 600℃; The holding time is 10-15min; The first reducing rate is 30℃ / min.

9. A silicon carbide thick film, characterized by, The silicon carbide thick film is obtained by the epitaxial growth method according to any one of claims 1-8.

10. The silicon carbide thick film according to claim 9 in the preparation of a high-voltage device of a megavolt level.

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