Growth method of silicon carbide epitaxial wafer and silicon carbide epitaxial wafer

Abstract

The invention provides a growth method of a silicon carbide epitaxial wafer and the silicon carbide epitaxial wafer, and the growth method comprises the steps: conveying a silicon carbide substrate into a reaction chamber under the condition that the reaction chamber has initial pressure and initial temperature, and conveying hydrogen into the reaction chamber; carrying out temperature rise and pressure reduction operation on the reaction chamber so as to carry out in-situ etching on the silicon carbide substrate; heating and depressurizing the reaction chamber, simultaneously reducing the flow of hydrogen, introducing a carbon source and a silicon source into the reaction chamber, and bringing tris (dimethylamino) silane into the reaction chamber by using hydrogen to grow a buffer layer; increasing the flow of the carbon source introduced into the reaction chamber, reducing the flow of the hydrogen, and growing a main epitaxial layer; and after epitaxial growth is completed, closing the reaction gas, cooling and boosting, and taking out the silicon carbide epitaxial wafer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a growth method of silicon carbide epitaxial wafer and silicon carbide epitaxial wafer. BACKGROUND

[0002] Silicon carbide (SiC), as an important third-generation semiconductor material, has been widely used in high-power, high-frequency and extreme conditions in recent years due to its unique physical and chemical properties, such as wider band gap, higher avalanche critical electric field, better thermal conductivity, wider working temperature range and excellent chemical stability, especially in the field of power electronics. The key to SiC power devices lies in its high-quality epitaxial layer, among which n-type doped silicon carbide epitaxial wafer is particularly important, as it directly affects the efficiency and reliability of the device. At present, the commonly used n-type doping gas sources mainly include nitrogen (N2) and ammonia (NH3). Nitrogen needs to be decomposed at high temperature to provide nitrogen atoms for doping, while ammonia can directly decompose to provide active nitrogen source. These two methods are standard means to achieve n-type doping of SiC epitaxial wafer.

[0003] However, using nitrogen as an n-type doping source has obvious limitations. The N≡N bond energy of nitrogen is as high as 946 kJ / mol, which means that nitrogen needs to be decomposed at a very high temperature, and this high decomposition temperature significantly reduces the doping efficiency, requiring a large gas flow to compensate for the efficiency loss, which often leads to residual gas in the chamber and so-called "memory effect", thereby affecting the subsequent growth quality and uniformity.

[0004] On the other hand, although ammonia has a lower decomposition temperature, it is easy to react with silicon source at high temperature to generate undesirable parasitic compounds such as SiNx, which not only reduces the quality of the epitaxial layer, but also affects the performance of the final device. SUMMARY

[0005] The main purpose of the present application is to provide a growth method of silicon carbide epitaxial wafer and silicon carbide epitaxial wafer, to solve the problems of low high-temperature decomposition efficiency of n-type dopant (such as N2) and easy generation of by-products of ammonia (NH3) in the prior art.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a growth method of silicon carbide epitaxial wafer is provided, comprising:

[0007] Under the condition that the reaction chamber has an initial pressure and an initial temperature, the silicon carbide substrate is transported into the reaction chamber, and hydrogen gas is delivered into the reaction chamber;

[0008] The reaction chamber is subjected to temperature rising and pressure reducing operation to etch the silicon carbide substrate in situ;

[0009] The reaction chamber is heated and depressurized, while the flow rate of hydrogen is reduced. A carbon source and a silicon source are introduced into the reaction chamber, and the hydrogen is used to carry tris(dimethylamino)silane into the reaction chamber for buffer layer growth.

[0010] Increase the flow rate of carbon source into the reaction chamber and decrease the flow rate of hydrogen to grow the main epitaxial layer;

[0011] After epitaxial growth is complete, the reaction gas is turned off, the temperature is lowered and the pressure is increased, and the silicon carbide epitaxial layer is removed.

[0012] Furthermore, the initial pressure is between 800 mbar and 1200 mbar, preferably 1000 mbar; and / or the initial temperature is between 600°C and 900°C, preferably 800°C; and / or the flow rate of hydrogen supplied to the reaction chamber is between 120 slm and 200 slm, preferably 160 slm.

[0013] Furthermore, during the heating and depressurization operation of the reaction chamber, the first target temperature of the reaction chamber is between 1450°C and 1650°C, preferably 1550°C; the first target pressure of the reaction chamber is between 100 mbar and 150 mbar, preferably 120 mbar. After the real-time temperature and pressure of the reaction chamber reach the first target temperature and pressure respectively, the pressure is maintained for a set time of 12 min to 18 min, preferably 15 min, to perform in-situ etching of the silicon carbide substrate.

[0014] Furthermore, during the heating process of the reaction chamber, the heating time of the reaction chamber is 10 minutes.

[0015] Furthermore, during the heating and depressurization operation of the reaction chamber, the second target temperature of the reaction chamber is between 1600℃ and 1650℃, preferably 1625℃; and / or, the temperature rise rate of the reaction chamber from the first target temperature to the second target temperature is between 8℃ / min and 15℃ / min, preferably 10℃ / min.

[0016] Furthermore, during the process of heating and depressurizing the reaction chamber while reducing the hydrogen flow rate, the hydrogen flow rate is reduced to between 90 slm and 120 slm, preferably 100 slm; the reaction chamber pressure is reduced from the first target pressure to between 40 mbar and 60 mbar, preferably 50 mbar.

[0017] Furthermore, during the process of introducing a carbon source and a silicon source into the reaction chamber, the carbon source is ethylene and the silicon source is trichlorosilane; and / or, the carbon source gas flow rate is 60 sccm to 90 sccm, preferably 85 sccm; and / or, the molar ratio of the introduced carbon source to the silicon source is 0.9:1.2, preferably 1.0.

[0018] Furthermore, during the process of using hydrogen to carry tris(dimethylamino)silane into the reaction chamber, the tris(dimethylamino)silane is stored in a bubbler, and the temperature of the bubbler is controlled between 35°C and 45°C. Hydrogen is controlled to be input into the bubbler at a set flow rate, carrying the tris(dimethylamino)silane into the reaction chamber; wherein, the set flow rate is 80 sccm to 120 sccm, preferably, the set flow rate is 100 sccm.

[0019] Furthermore, in the process of increasing the flow rate of carbon source into the reaction chamber and reducing the flow rate of hydrogen, the flow rate of carbon source is controlled to increase from 60 sccm to 90 sccm to 300-600 sccm, preferably 510 sccm, while the molar ratio of carbon source to silicon source remains unchanged, and the flow rate of hydrogen is reduced to between 70 slm and 90 slm, preferably 85 slm.

[0020] According to another aspect of the present invention, a silicon carbide epitaxial wafer is provided, which is prepared by the above-described silicon carbide epitaxial wafer growth method.

[0021] By applying the technical solution of this invention, using TDMAS as an n-type doping source, combined with specific growth temperature and hydrogen flow rate control, the doping efficiency can be effectively improved while ensuring the uniformity of doping concentration and reducing the generation of by-products. In the prior art, TDMAS has not been selected as a traditional silicon carbide epitaxial doping source, mainly due to its thermal stability and the complexity of its decomposition path. At high temperatures, it decomposes into dimethylamine radicals and silane derivatives, and its organic groups (-N(CH3)2) may produce carbon residues, contaminating the SiC epitaxial layer; decomposition by-products (such as carbon-containing gaseous substances) may react with the Si / H / C system to form amorphous carbon or other impurities. Furthermore, compared to direct gas-phase doping (such as N2), TDMAS needs to be carried from the bubbler by a carrier gas (H2), and the evaporation stability of liquid sources is significantly affected by temperature / pressure fluctuations, requiring precise control of the bubbler outlet concentration.

[0022] To address the aforementioned issues, this application employs a low-pressure environment to suppress side reactions, utilizing a 50 mbar low-pressure reaction chamber to significantly reduce the TDMAS gas-phase residence time, preventing the carbonization of organic groups. Furthermore, it employs "temperature-coordinated optimization," using 1550℃ pre-etching to remove surface oxygen (preventing Si-O bond interference with doping), and a 1625℃ growth temperature to promote the complete decomposition of TDMAS into Si-N bonds, with organic groups reduced by H2 to volatile CH4 / NH3. This resolves the issue of potential impurities in the products during the TDMAS decomposition process. Additionally, by progressively reducing the H2 flow rate from 160 slm to 100 slm, gas-phase nucleation is suppressed while maintaining uniform TDMAS transport. To address the issue of the stability of liquid source evaporation being affected by temperature / pressure fluctuations, the hydrogen flow rate delivered to the bubbler in this application must be strictly within the 80-120 sccm window, while the bubbler temperature is controlled at 35-45℃. If the flow rate is too low (<80 sccm), the concentration at the bubbler outlet will be too high, which will easily cause condensation in the pipeline; if it is too high (>120 sccm), the partial pressure of TDMAS will decrease, and the doping efficiency will drop sharply. Temperature control is mainly because if the temperature in the pipeline entering the high-temperature reaction chamber is not properly controlled or there is local overheating, TDMAS may decompose prematurely or undergo side reactions, leading to pipeline blockage, unstable doping efficiency, or introduction of contamination.

[0023] This application uses TDMAS as the n-type dopant source because TDMAS can decompose at relatively low temperatures (150℃~300℃), which is lower than the formation temperature of silicon carbide (1500℃~1700℃), resulting in higher decomposition efficiency and significantly reducing the need for high temperatures. This not only improves doping efficiency but also reduces energy consumption. By generating TDMAS under a low-pressure environment of 50 Mbr, the residence time of TDMAS in the reaction chamber is significantly shortened, effectively avoiding the residue and memory effect of gaseous dopants, thus ensuring uniformity and stability during the doping process, and further improving the uniform doping quality of the epitaxial wafer. The organic groups after TDMAS decomposition are reduced to volatiles in the H2 environment. The process avoids the formation of byproducts such as volatile CH4 and NH3, rather than impurities such as SiNx. Furthermore, pre-etching at 1550℃ removes surface oxygen, and the growth temperature of 1625℃ completely decomposes TDMAS, ensuring that the decomposition products do not react with SiC growth to produce byproducts. This significantly improves the crystal quality and purity of the SiC epitaxial wafer. This application achieves precise control of doping concentration by accurately controlling the evaporation and carrying of TDMAS, combined with optimized growth conditions. TDMAS not only provides N atoms for n-type doping but also provides Si atoms to participate in SiC lattice growth, optimizing the C / Si ratio, avoiding the formation of SiNx, and ensuring efficient utilization of the dopant and stability of the doping concentration.

[0024] By gradually reducing the H2 flow rate from 160 slm to 100 slm and controlling the TDMAS-carrying flow rate within the range of 80 sccm-120 sccm, uniform transport and complete decomposition of TDMAS were ensured, while gas-phase nucleation was suppressed, maintaining a stable supply of carbon and silicon sources. This overcame the problem caused by the high flow rate requirement of dopants. Furthermore, by increasing the carbon source gas to the range of 300-600 sccm and reducing the H2 flow rate to 85 slm, the optimal C / Si ratio was maintained within the range of 0.9-1.2. This effectively uniformly promoted the nucleation of impurity crystal forms, optimized the crystal structure of SiC epitaxial wafers, and overcame the problem of by-product formation. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 The embodiment shown in this application uses tris(dimethylamino)silane (TDMAS) as the n-type dopant source, with a target doping concentration of 1.0e16 cm⁻¹. -3 The doping concentration;

[0027] Figure 2 The doping concentration of the grown silicon carbide epitaxial wafer is shown when nitrogen (N2) is used as the n-type doping source. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Silicon carbide (SiC), as an important third-generation semiconductor material, has been widely used in recent years under high-power, high-frequency, and extreme conditions, especially in the field of power electronics, due to its unique physical and chemical properties, such as a wider bandgap, higher avalanche critical electric field, better thermal conductivity, wider supported operating temperature range, and excellent chemical stability. The key to SiC power devices lies in their high-quality epitaxial layers, among which n-type doped SiC epitaxial wafers are particularly important, directly affecting the device's efficiency and reliability. Currently, commonly used n-type doping gas sources mainly include nitrogen (N2) and ammonia (NH3). Nitrogen gas needs to decompose at high temperatures to provide nitrogen atoms for doping, while ammonia gas can directly decompose to provide an active nitrogen source. Both methods are standard means of achieving n-type doping of SiC epitaxial wafers.

[0030] However, using nitrogen as an n-type doping source has significant limitations. The N≡N bond energy of nitrogen is as high as 946 kJ / mol, which means that nitrogen needs to be decomposed at extremely high temperatures. This high decomposition temperature significantly reduces the doping efficiency, requiring a large gas flow rate to compensate for the efficiency loss. This often leads to residual gas in the cavity and the so-called "memory effect," which in turn affects the subsequent growth quality and uniformity.

[0031] On the other hand, although ammonia decomposes at a lower temperature, it is prone to react with silicon sources at high temperatures to generate undesirable parasitic compounds such as SiNx. These compounds not only reduce the quality of the epitaxial layer but also affect the performance of the final device.

[0032] To address the aforementioned problems, this application provides a method for growing silicon carbide epitaxial wafers and the silicon carbide epitaxial wafer itself, thereby solving the problems of low high-temperature decomposition efficiency of n-type dopants (such as N2) and easy generation of ammonia (NH3) as byproducts in the prior art.

[0033] Example 1

[0034] This application provides a method for growing silicon carbide epitaxial wafers, including:

[0035] With initial pressure and initial temperature in the reaction chamber, the silicon carbide substrate is transferred into the reaction chamber, and hydrogen is supplied into the reaction chamber.

[0036] The reaction chamber is heated and depressurized to perform in-situ etching of the silicon carbide substrate;

[0037] The reaction chamber is heated and depressurized, while the flow rate of hydrogen is reduced. A carbon source and a silicon source are introduced into the reaction chamber, and the hydrogen is used to carry tris(dimethylamino)silane into the reaction chamber for buffer layer growth.

[0038] Increase the flow rate of carbon source into the reaction chamber and decrease the flow rate of hydrogen to grow the main epitaxial layer;

[0039] After epitaxial growth is complete, the reaction gas is turned off, the temperature is lowered and the pressure is increased, and the silicon carbide epitaxial wafer is removed.

[0040] The main chemical reactions that occur during the growth of the main epitaxial layer are as follows:

[0041] The main epitaxial growth reaction is: SiHCl3(g) + C2H4(g) → SiC(s) + 3HCl(g) + H2(g);

[0042] TDMAS pyrolysis and doping process: Initial pyrolysis: SiH(N(CH3)2)3→SiH(N(CH3)2)2+·N(CH3)2;

[0043] SiH(N(CH3)2)2→SiH(N(CH3)2)+·N(CH3)2;

[0044] Intermediate pyrolysis: SiH(N(CH3)2)→SiH2+·N(CH3)2;

[0045] Further pyrolysis:

[0046] ·N(CH3)2→·NHCH3+CH3; ·NHCH3→·NH2+CH3; ·NH2→·NH+·H.

[0047] The ·NH generated by the cracking provides the active nitrogen atoms required for doping, replacing the carbon atoms in the silicon carbide lattice to form N-type doping. In this process, other by-products are also generated, which are mainly discharged from the chamber with the gas flow.

[0048] The silicon carbide substrate is loaded into the reaction chamber under specific initial pressure (e.g., 800-1200 mbar) and temperature (e.g., 600-900 °C).

[0049] Hydrogen gas is introduced into the reaction chamber to initially establish a hydrogen atmosphere in preparation for pretreatment.

[0050] The reaction chamber is then heated (to 1450-1650°C) and depressurized (to 100-150 mbar) to prepare for in-situ etching of the silicon carbide substrate.

[0051] At this stage, adjusting the hydrogen flow rate to a lower level (e.g., 90-120 slm) helps the etching process, removes oxides from the silicon carbide substrate surface, cleans the surface, and creates favorable conditions for subsequent growth.

[0052] Continue to heat the reaction chamber (to 1600-1650°C) and depressurize it (to 40-60 mbar), while reducing the hydrogen flow rate to an optimized level (e.g., 70-90 slm).

[0053] A carbon source (such as ethylene) and a silicon source (such as trichlorosilane) are introduced initially, and TDMAS (tris(dimethylamino)silane) is introduced into the reaction chamber using hydrogen gas to grow a buffer layer. The growth rate at this stage is low, approximately 0.15-0.3 μm / min, to provide a high-quality interface for the subsequent growth of the main epitaxial layer.

[0054] While maintaining the reaction temperature and pressure, increasing the carbon source flow rate to a higher level (e.g., 300-600 sccm) accelerates epitaxial layer growth, increasing the growth rate to approximately 0.8-3 micrometers / min.

[0055] At the same time, the hydrogen flow rate is further reduced to increase the partial pressure of TDMAS and ensure the stability and uniformity of the n-type doping concentration.

[0056] After growth is complete, shut off all reaction gases, gradually reduce the temperature of the reaction chamber, and increase the hydrogen flow rate to a higher level (e.g., 100-200 sccm) to help dissipate heat and avoid introducing impurities.

[0057] The pressure in the reaction chamber was gradually restored to atmospheric pressure, and finally the silicon carbide epitaxial wafer was safely removed from the reaction chamber.

[0058] By using TDMAS as an n-type doping source, combined with specific growth temperature and hydrogen flow rate control, the doping efficiency can be effectively improved while ensuring the uniformity of doping concentration and reducing the generation of by-products.

[0059] By optimizing the low-pressure environment and temperature, the formation of TDMAS decomposition byproducts (such as SiNx) was avoided, thus improving the purity of the epitaxial layer.

[0060] By gradually controlling the temperature and gas flow rate, precise control of epitaxial growth conditions can be achieved, avoiding gas-phase nucleation and maintaining a stable C / Si ratio, thereby improving the growth quality and growth rate of the epitaxial layer.

[0061] This method achieves efficient and high-quality continuous growth of silicon carbide epitaxial wafers by strictly controlling growth parameters, thereby improving production efficiency. At the same time, it can stabilize and repeat the growth process, ensuring the consistency of epitaxial wafer quality.

[0062] Furthermore, the initial pressure is between 800 mbar and 1200 mbar, preferably 1000 mbar.

[0063] In silicon carbide epitaxial wafer growth methods, the initial pressure setting has a crucial impact on the overall growth process. Setting the initial pressure between 800 mbar and 1200 mbar, and preferably 1000 mbar, aims to create an environment conducive to safe substrate loading and preliminary processing, while reducing the infiltration of external atmosphere and lowering the risk of SiC surface oxidation.

[0064] Before any growth process begins, the reaction chamber is set at a high initial pressure range (800-1200 mbar), which is close to atmospheric pressure. This facilitates the smooth and safe transfer of the silicon carbide substrate from the transfer chamber to the reaction chamber, avoiding deformation or damage to the silicon carbide substrate when the pressure changes drastically.

[0065] After the silicon carbide substrate is loaded, the hydrogen flow rate in the reaction chamber is regulated while the pressure is maintained at this preferred initial level. At a pressure of 1000 mbar, the hydrogen can effectively interact with the substrate surface, helping to remove oxides and contaminants, providing a clean starting environment for subsequent growth processes.

[0066] In the subsequent pre-etching and growth stages, the temperature and pressure are further adjusted to more suitable growth conditions (e.g., the temperature is increased to 1550°C and the pressure is reduced to 50 mbar during the pre-etching stage; the temperature is increased to 1625°C and the pressure is adjusted to 40-60 mbar during the growth stage). These adjustments are all aimed at optimizing the growth of the silicon carbide epitaxial layer while maintaining high doping efficiency and epitaxial layer quality.

[0067] After the growth process is completed, the pressure in the reaction chamber is gradually adjusted back to atmospheric pressure, and the substrate is cooled to room temperature under the protection of hydrogen gas. It is then safely removed into a transfer chamber filled with argon gas.

[0068] Higher initial pressure reduces the infiltration of external gases, especially in the early stages of silicon carbide substrate loading, effectively preventing surface oxidation under low pressure conditions. This is particularly important for SiC materials, as they are extremely sensitive to oxygen.

[0069] Under an initial pressure of 1000 mbar, the distribution of gases (such as hydrogen, silicon source, and carbon source) is more uniform and efficient, which is conducive to the rapid stabilization of subsequent growth conditions.

[0070] Precise control of the initial pressure within the reaction chamber lays the foundation for fine-tuning of temperature, pressure, and gas flow throughout the growth process. This helps to obtain higher-quality silicon carbide epitaxial wafers, reduce dislocation density, and improve material purity.

[0071] The choice of initial pressure is crucial for the decomposition and doping efficiency of TDMAS. With an appropriate initial pressure, subsequent adjustments to temperature and gas flow rate facilitate highly controllable n-type doping, thereby ensuring a uniform distribution of doping concentration in the epitaxial layer.

[0072] Furthermore, the initial temperature is between 600℃ and 900℃, preferably 800℃.

[0073] Silicon carbide substrates can quickly reach a stable state at an initial temperature of 800℃, avoiding substrate warping or thermal stress problems caused by temperature gradients and ensuring the flatness of the substrate during subsequent growth.

[0074] At a relatively high but controllable initial temperature, the oxide layer on the surface of the silicon carbide substrate is more easily removed by reducing gases such as hydrogen, thereby reducing the risk of oxide residue in the early stage of growth and improving the purity of the epitaxial layer.

[0075] Setting the initial temperature to 800℃ helps the subsequent growth stages transition to a more suitable temperature quickly, reducing the time required for temperature adjustment and improving production efficiency.

[0076] By starting the growth process at a suitable initial temperature, the decomposition of TDMAS can be better controlled, resulting in more uniform and controllable n-type doping and reducing doping inhomogeneity or byproduct formation caused by improper temperature.

[0077] Furthermore, the flow rate of hydrogen gas supplied to the reaction chamber is between 120 slm and 200 slm, preferably 160 slm.

[0078] Hydrogen gas has strong reducing properties at high temperatures, which can effectively remove the oxide layer on the surface of silicon carbide substrates, providing a clean starting interface for subsequent epitaxial growth. Especially in the pre-etching stage, optimizing the hydrogen flow rate can ensure that surface oxides are completely removed without introducing additional impurities.

[0079] An appropriate hydrogen flow rate helps to create a uniform gas distribution throughout the reaction chamber, which is crucial for the full reaction of the carbon and silicon sources. While a higher hydrogen flow rate (e.g., 200 slm) helps to homogenize the gas distribution, it increases the likelihood of gas-phase nucleation, while a lower flow rate (e.g., 120 slm) may not provide sufficient gas flow velocity to remove reaction byproducts in time. The preferred flow rate of 160 slm ensures uniform gas distribution while maintaining reaction kinetic balance, helping to reduce byproduct deposition on the substrate and improve the purity of the epitaxial layer.

[0080] Hydrogen, as the carrier gas, can carry TDMAS to the growth region within the reaction chamber. A hydrogen flow rate of 160 slm provides sufficient power to ensure uniform mixing of TDMAS with other reactant gases, while avoiding the reduction in TDMAS partial pressure that could be caused by excessively high hydrogen flow rates, which would affect its decomposition efficiency and doping ability.

[0081] The choice of hydrogen flow rate also affects the probability of gas-phase nucleation and the stability of the C / Si ratio. A flow rate of 160 slm can suppress gas-phase nucleation (the formation of Si clusters) while maintaining a suitable ratio between the carbon and silicon sources, avoiding surface enrichment of Si or C, and reducing defects during growth.

[0082] Optimized hydrogen flow rate (160 slm) in conjunction with growth temperature, pressure, and other gas flow rates helps to improve the growth rate of silicon carbide epitaxial wafers while maintaining good crystal quality. This is because hydrogen effectively removes byproducts during growth, reducing the generation of dislocations and other defects, while promoting the reaction between the carbon and silicon sources.

[0083] A suitable hydrogen flow rate not only improves the efficiency of epitaxial growth but also takes into account energy consumption and cost control. Excessive hydrogen flow rate not only wastes resources but may also increase the cost of maintaining the chamber, while a flow rate of 160 slm achieves high-quality growth while maintaining reasonable energy consumption.

[0084] Furthermore, during the heating and depressurization operation of the reaction chamber, the first target temperature of the reaction chamber is between 1450°C and 1650°C, preferably 1550°C; the first target pressure of the reaction chamber is between 100 mbar and 150 mbar, preferably 120 mbar. After the real-time temperature and pressure of the reaction chamber reach the first target temperature and pressure respectively, the pressure is maintained for a set time of 12 min to 18 min, preferably 15 min, to perform in-situ etching of the silicon carbide substrate.

[0085] At a high temperature of 1550℃, the oxide layer, contaminants, and impurities on the surface of the silicon carbide substrate are effectively removed through the reaction of hydrogen with the surface material. The higher temperature helps to accelerate the interaction between hydrogen and the SiC surface, ensuring that the surface reaches an ideal clean state and providing a smooth, defect-free growth interface for subsequent epitaxial growth.

[0086] By reducing the pressure to 120 mbar, the gas molecule density within the reaction chamber was significantly reduced, lowering the collision frequency between gases and thus minimizing unwanted side reactions. This is particularly important when using TDMAS as a dopant source; the low-pressure environment helps prevent the formation of TDMAS decomposition byproducts, such as amorphous carbon or other impurities, thereby improving the purity of the epitaxial layer.

[0087] There is a balance between the target temperature of 1550℃ and the target pressure of 120mbar. Too high a temperature may lead to SiC volatilization loss, while too low a pressure may reduce etching efficiency. The preferred settings of 1550℃ and 120mbar minimize the pyrolysis loss of SiC while ensuring sufficient surface etching, thus preparing an optimized environment for epitaxial growth.

[0088] After reaching the first target temperature and pressure, the set time of 15 minutes provides a sufficient time window for the etching process to proceed fully and uniformly. It also ensures that the temperature and pressure distribution in the reaction chamber reaches a stable state, creating stable starting conditions for the subsequent growth of the buffer layer and epitaxial layer.

[0089] In-situ etching under optimized temperature and pressure conditions can significantly improve the efficiency of subsequent epitaxial growth and the quality of the epitaxial layer. The clean surface after etching helps increase growth rate and reduce dislocations and defects. Meanwhile, stable and optimized growth conditions ensure the uniformity and controllability of the epitaxial layer, which is crucial for device performance and reliability.

[0090] Furthermore, during the heating process of the reaction chamber, the heating time of the reaction chamber is 10 minutes.

[0091] Controlling the heating rate, particularly setting the heating time to 10 minutes, helps ensure a uniform temperature distribution within the reaction chamber. This process allows the silicon carbide substrate surface and other parts of the chamber to gradually adapt to the high-temperature environment, reducing the temperature gradient and thus avoiding thermal stress and resulting dislocations or other defects that may occur during growth.

[0092] Silicon carbide is highly sensitive to temperature changes, and rapid temperature changes can generate thermal stress within the substrate. Setting the heating time to 10 minutes can avoid drastic temperature changes, thereby reducing stress caused by uneven thermal expansion of the substrate, reducing the risk of cracks and peeling, and ensuring the integrity and reliability of the epitaxial wafer.

[0093] During the pre-etching stage, the temperature of the reaction chamber needs to be raised to approximately 1550°C. An appropriate heating time ensures the sufficiency and controllability of the reaction between hydrogen and the SiC surface, helping to remove the oxide layer and contaminants, thus preparing for high-quality epitaxial layer growth. A heating time of 10 minutes is neither too long, leading to increased energy consumption, nor too short, resulting in incomplete pre-etching.

[0094] By controlling the heating rate, a smooth transition to the temperature conditions required for subsequent growth can be achieved. This helps maintain the dynamic equilibrium of the gas reaction, avoiding an excessively rapid reaction rate due to a sudden increase in temperature, which could affect the growth quality of the epitaxial layer. Stable temperature changes contribute to uniform gas distribution and decomposition, reduce byproduct formation, and improve doping efficiency and uniformity.

[0095] Furthermore, during the heating and depressurization operation of the reaction chamber, the second target temperature of the reaction chamber is between 1600℃ and 1650℃, preferably 1625℃.

[0096] At 1625℃, the growth rate of SiC is optimized, balancing growth speed and crystal quality. Excessively high temperatures (such as close to 1700℃) accelerate the sublimation rate of SiC, resulting in a growth rate lower than the sublimation rate, leading to a "negative growth" phenomenon. Conversely, excessively low temperatures reduce the growth rate. The 1625℃ temperature ensures rapid and uniform growth of the epitaxial layer, improving production efficiency.

[0097] Within the temperature range of 1600℃ to 1650℃, the step flow growth mechanism on the SiC surface is more pronounced, effectively eliminating basal plane dislocations (BPD). The preferred temperature of 1625℃ helps promote perfect alignment of the SiC lattice, reducing dislocation density and thus obtaining high-quality epitaxial wafers.

[0098] As an n-type dopant source, TDMAS can achieve more thorough decomposition at a high temperature of 1625℃, releasing sufficient active nitrogen (N) atoms and silicon (Si) atoms. The active nitrogen atoms can be efficiently incorporated into the SiC lattice to achieve n-type doping, while the silicon atoms participate in the formation of the SiC lattice, reducing impurity residue. At this temperature, the decomposition path of TDMAS is more optimized, reducing the formation of byproducts (such as SiNx, HCN, NH3, and CH4) and improving the uniformity and stability of doping.

[0099] A growth temperature of 1625℃ helps suppress the nucleation of impurity crystal forms, especially by controlling the flow rates of the carbon and silicon sources to achieve a C / Si ratio of 0.9-1.2, which can further reduce the possibility of impurity nucleation. Growth conditions at this temperature help form a pure silicon carbide epitaxial layer, reducing impurities and defects that may be introduced during the growth process.

[0100] Furthermore, the temperature rise rate of the reaction chamber from the first target temperature to the second target temperature is between 8°C / min and 15°C / min, preferably 10°C / min.

[0101] Controlling the temperature rise rate can significantly reduce the thermal shock to the silicon carbide substrate, avoiding increased stress within the substrate material due to sudden temperature changes, thereby reducing the generation of dislocations and other thermodynamic defects. An optimal rate of 10 °C / min ensures that the temperature quickly reaches the growth conditions while giving the silicon carbide substrate and the entire system sufficient time to adapt to temperature changes, reducing unplanned defects during the growth process.

[0102] Precise control of the temperature rise rate helps to smoothly transition to more suitable growth conditions. Too rapid a temperature rise (e.g., close to 15°C / min) may lead to uneven temperature distribution within the system, while too slow a rise (e.g., close to 8°C / min) will prolong the process and increase energy consumption. A temperature rise rate of 10°C / min balances temperature uniformity and economy, ensuring efficient subsequent growth.

[0103] During the transition from the pre-etching temperature to the growth temperature, an appropriate temperature rise rate helps to efficiently decompose reactants such as TDMAS. A temperature rise rate of 10 °C / min ensures that TDMAS gradually decomposes before reaching the growth temperature, releasing the required active nitrogen and silicon atoms, thereby improving doping efficiency and the growth quality of the SiC epitaxial layer.

[0104] Furthermore, during the process of heating and depressurizing the reaction chamber while reducing the hydrogen flow rate, the hydrogen flow rate is reduced to between 90 slm and 120 slm, preferably 100 slm; the reaction chamber pressure is reduced from the first target pressure to between 40 mbar and 60 mbar, preferably 50 mbar.

[0105] By reducing the hydrogen flow rate to 100 slm, gas-phase nucleation during growth, particularly the formation of Si clusters, can be effectively suppressed. Once formed, these clusters can interfere with the normal growth of the SiC lattice, leading to defects in the epitaxial layer. A moderate hydrogen flow rate maintains a favorable gas environment, reduces the formation of these nucleation clusters, and improves the purity and quality of the epitaxial layer.

[0106] With a reduced hydrogen flow rate, the partial pressure of TDMAS (tris(dimethylamino)silane) relatively increases, which helps to improve the incorporation efficiency and uniformity of nitrogen atoms. A hydrogen flow rate of 100 slm maintains good gas mixing while avoiding over-dilution or over-concentration of TDMAS, ensuring uniform distribution of the dopant and thus achieving uniform doping concentration in the epitaxial layer.

[0107] At the growth temperature, reducing the hydrogen flow rate while lowering the pressure in the reaction chamber to 50 mbar helps accelerate the removal of TDMAS decomposition products (such as volatile CH4 / NH3). The low-pressure environment reduces the residence time of byproducts in the chamber, lowers the risk of secondary deposition, and ensures a clean growth interface.

[0108] By adjusting the hydrogen flow rate and reaction chamber pressure, an appropriate C / Si ratio between the carbon and silicon sources was maintained. At a hydrogen flow rate of 100 slm and a chamber pressure of 50 mbar, the transport and reaction of the carbon and silicon sources could be effectively controlled, avoiding surface Si or C enrichment and reducing the nucleation of impurity crystals that may occur during growth.

[0109] Furthermore, during the process of introducing a carbon source and a silicon source into the reaction chamber, the carbon source is ethylene and the silicon source is trichlorosilane.

[0110] Ethylene and trichlorosilane serve as carbon and silicon sources, respectively, and their molecular structures and chemical properties are highly suitable for the epitaxial growth of SiC. Ethylene has a low boiling point and high reactivity, readily decomposing at high temperatures and reacting with SiHCl3 to generate the carbon and silicon elements required for SiC. This highly efficient chemical conversion process significantly improves the speed and yield of epitaxial growth.

[0111] Using ethylene and trichlorosilane as reaction sources can significantly improve the quality of SiC crystals. Their chemical decomposition pathways are relatively direct, and the generated byproducts (such as HCl and H2) are easily removed, reducing the introduction of impurities and defects. In addition, an appropriate carbon-to-silicon source ratio (carbon-to-silicon molar ratio of 0.9-1.2, preferably 1.0) helps suppress the nucleation of impurity crystal forms, ensuring that the SiC epitaxial layer has high purity and low dislocation density.

[0112] When using TDMAS as an n-type dopant, ethylene and trichlorosilane, as the main growth sources, allow for better control of dopant decomposition and doping efficiency. The ratio of carbon to silicon sources directly affects the growth conditions of SiC, which in turn influences the decomposition path of TDMAS, ensuring an effective supply of active nitrogen atoms and improving the uniformity and controllability of doping.

[0113] Furthermore, the carbon source gas flow rate is 60 sccm to 90 sccm, preferably 85 sccm.

[0114] The adjustment of the carbon source gas flow rate directly affects the C / Si ratio during SiC growth. A preferred flow rate of 85 sccm ensures that the molar ratio between the carbon and silicon sources is within the optimal range of 0.9 to 1.2, preferably 1.0. This ratio helps suppress impurity nucleation under Si-rich or C-rich conditions, reduces the aggregation of surface steps and the formation of triangular defects, thereby improving the quality and purity of the SiC epitaxial layer.

[0115] Appropriate carbon source gas flow rate controls the growth rate and avoids instability during the growth process. Too low a flow rate (e.g., below 60 sccm) may result in a slow growth rate, increasing production cycle time and cost; while too high a flow rate (e.g., above 90 sccm) may lead to excessively concentrated carbon source deposition, affecting the uniformity and structural integrity of the SiC epitaxial layer. A flow rate of 85 sccm achieves an ideal balance between growth rate and crystal quality.

[0116] The regulation of carbon source gas flow rate also affects the doping uniformity in the epitaxial layer. At the optimized flow rate, gas mixing is more uniform, which helps TDMAS (tris(dimethylamino)silane) to decompose and be incorporated uniformly within the chamber, thereby achieving a uniform distribution of doping concentration in the epitaxial layer and improving the performance consistency of the device.

[0117] Setting the carbon source gas flow rate between 60 sccm and 90 sccm, preferably 85 sccm, helps enhance the stability of the entire growth process. A stable flow rate ensures a continuous supply of gas components, reduces fluctuations in growth conditions, and improves the repeatability of epitaxial growth, which is crucial for the mass production of high-quality SiC epitaxial wafers.

[0118] Furthermore, the molar ratio of the carbon source to the silicon source is 0.9:1.2, preferably 1.0.

[0119] Controlling the molar ratio of carbon to silicon sources is crucial for suppressing the nucleation of non-SiC crystalline phases. At an optimal molar ratio of 1.0, the supply of carbon and silicon is proportionally matched, reducing conditions of excessive Si or C enrichment, effectively suppressing the nucleation of amorphous or other carbides, and improving the purity and crystal quality of the SiC epitaxial layer.

[0120] An appropriate C / Si molar ratio can balance growth rate and crystal quality. If the C / Si ratio deviates from the preferred range, too low a ratio will lead to a decrease in growth rate, and excess Si source may form droplets, affecting crystallization; too high a ratio may lead to carbon enrichment on the surface, causing step aggregation and triangular defects. The preferred molar ratio of 1.0 ensures that high growth rate and high purity of SiC are achieved simultaneously.

[0121] Precise control of the molar ratio of carbon to silicon sources also affects doping efficiency. At a molar ratio of 1.0, nitrogen atoms (derived from TDMAS decomposition) during epitaxial growth can be incorporated into the SiC lattice more efficiently, resulting in a uniform n-type doping effect.

[0122] Furthermore, in the process of using hydrogen to carry tris(dimethylamino)silane into the reaction chamber, the hydrogen is used to store the tris(dimethylamino)silane in a bubbler, and the temperature of the bubbler is controlled between 35°C and 45°C. The hydrogen is controlled to be input into the bubbler at a set flow rate, and carries the tris(dimethylamino)silane into the reaction chamber; wherein, the set flow rate is 80 sccm to 120 sccm, preferably, the set flow rate is 100 sccm.

[0123] Maintaining the bubbler temperature between 35°C and 45°C ensures a suitable evaporation rate for TDMAS in its liquid state, avoiding evaporation instability caused by excessively high or low temperatures. Within this temperature range, the vapor pressure of TDMAS is moderate, allowing for uniform mixing with hydrogen. A hydrogen flow rate of 100 sccm provides sufficient power to stably carry the TDMAS vapor into the reaction chamber, thus ensuring precise dopant transport.

[0124] At temperatures between 35°C and 45°C, TDMAS vapor does not easily condense in the piping leading to the high-temperature reaction chamber. Too low a hydrogen flow rate (e.g., below 80 sccm) may cause localized condensation of the TDMAS vapor within the piping, leading to solid blockages. Conversely, too high a flow rate (e.g., exceeding 120 sccm) will dilute the TDMAS vapor, reducing doping efficiency. A hydrogen flow rate of 100 sccm represents the optimal balance, ensuring unobstructed piping and effective utilization of the TDMAS.

[0125] Hydrogen gas is mixed with TDMAS at a preferred flow rate of 100 sccm and introduced into the reaction chamber. This helps maintain a uniform distribution of TDMAS vapor during growth, thereby improving the uniformity of the dopant throughout the SiC epitaxial layer and the stability of the doping process. This directly affects the consistency of the electrical properties of the final epitaxial wafer and is beneficial for optimizing device performance.

[0126] When TDMAS decomposes in the high-temperature reaction chamber, the resulting byproducts, such as organic groups, can be reduced by hydrogen to volatile compounds (such as CH4 and NH3) and then removed from the reaction chamber with the gas flow. The hydrogen flow rate of 100 sccm not only carries TDMAS vapor but also provides enough hydrogen to react with these byproducts, ensuring the cleanliness of the reaction chamber and reducing the possibility of impurity introduction.

[0127] Furthermore, in the process of increasing the flow rate of carbon source into the reaction chamber and reducing the flow rate of hydrogen, the flow rate of carbon source is controlled to increase from 60 sccm to 90 sccm to 300-600 sccm, preferably 510 sccm, while the molar ratio of carbon source to silicon source remains unchanged, and the flow rate of hydrogen is reduced to between 70 slm and 90 slm, preferably 85 slm.

[0128] The increase in carbon source gas flow rate directly led to a significant improvement in the SiC growth rate. During the growth process, the carbon source is crucial for SiC lattice formation. Increasing its flow rate provides more carbon atoms, accelerating the chemical vapor deposition (CVD) reaction rate, thereby increasing the epitaxial growth speed, shortening the entire production cycle, and improving production efficiency.

[0129] Although the carbon source flow rate is significantly increased, by reducing the hydrogen flow rate to 85 slm, the carbon-silicon molar ratio can still be maintained within the optimal range of 0.9 to 1.2, preferably 1.0. This ensures that the growth rate is increased while the quality of the SiC crystal is not affected, avoiding carbon-rich or silicon-rich phenomena caused by excess carbon source, and maintaining the ideal structure of the SiC lattice.

[0130] While reducing the hydrogen flow rate to 85 slm, the flow rate of hydrogen 2 (used to carry TDMAS) is maintained between 80 sccm and 120 sccm, preferably 100 sccm. This flow rate adjustment ensures stable input and decomposition of TDMAS, maintaining the uniformity and efficiency of n-type doping even under high carbon source inlet conditions, which is beneficial to the consistency of device performance.

[0131] By precisely controlling the carbon source and hydrogen flow rate, the stability and controllability of the entire epitaxial growth process can be enhanced. Appropriate carbon source increase rates and hydrogen flow rate decrease rates avoid drastic fluctuations in gas pressure and temperature, ensuring stable growth conditions and facilitating the mass production of high-quality SiC epitaxial wafers.

[0132] like Figure 1 Using tris(dimethylamino)silane (TDMAS) as the n-type dopant source, after continuously growing 10 batches of n-type doped silicon carbide epitaxial wafers according to the embodiments of this application, the target doping concentration is 1.0e16 cm⁻¹. -3 The doping concentration of TDMAS was measured. This indicates that using TDMAS as a dopant can achieve stable doping concentration control, with better uniformity and stability than traditional methods, thus verifying the effectiveness and advantages of this method.

[0133] Figure 2 This demonstrates the doping concentration of silicon carbide epitaxial wafers grown using nitrogen (N2) as the n-type doping source under the same process parameters. Compared to Figure 1 The doping effect of TDMAS is superior to that achieved with nitrogen as a dopant, resulting in doping uniformity and stability that are difficult to achieve. This further highlights the necessity and innovation of choosing TDMAS as a doping source, as well as its significant effectiveness in solving problems associated with traditional doping techniques.

[0134] Example 2

[0135] This application provides a silicon carbide epitaxial wafer based on the above embodiments, which is prepared by the above-described silicon carbide epitaxial wafer growth method.

[0136] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0137] First, the silicon carbide substrate is placed in a hydrogen atmosphere and pretreated using a preset pressure (800-1200 mbar, preferably 1000 mbar) and temperature (600-900 °C, preferably 800 °C). Then, the conditions are adjusted to 1450-1650 °C (preferably 1550 °C) and 120 mbar, with a hydrogen flow rate of 160 slm, for pre-etching to remove oxygen and impurities from the surface, providing a clean and active surface environment for subsequent epitaxial growth.

[0138] After pre-etching, the growth temperature is further increased to 1600-1650℃ (preferably 1625℃), the hydrogen flow rate is reduced to 90-120 slm (preferably 100 slm), and the reaction chamber pressure is reduced to 40-60 mbar (preferably 50 mbar). This series of controlled conditions not only optimizes the growth rate of SiC but also improves the quality and purity of the crystal.

[0139] During the growth stage of the main epitaxial layer, the molar ratio of carbon source gas (ethylene) to silicon source (trichlorosilane) is strictly controlled between 0.9 and 1.2, preferably 1.0, in order to suppress impurity nucleation, balance the growth rate and crystal quality, and improve doping efficiency.

[0140] Tris(dimethylamino)silane (TDMAS) was used as the n-type dopant source and stored in a bubbler with the temperature controlled at 35-45°C (preferably 40°C). By controlling the hydrogen flow rate at 80-120 sccm (preferably 100 sccm), the effective carrying and decomposition of TDMAS was maintained, achieving efficient and uniform doping with low energy consumption.

[0141] During the growth of the main epitaxial layer, by increasing the carbon source gas flow rate to 300-600 sccm (preferably 510 sccm) while keeping the molar ratio of carbon source to silicon source constant, and reducing the hydrogen flow rate to 70-90 slm (preferably 85 slm), the growth rate is significantly improved while maintaining a stable C / Si ratio, without sacrificing the uniformity and stability of the material.

[0142] This method significantly improves the growth rate of SiC epitaxial layers while maintaining extremely high crystal quality and purity, effectively suppressing impurity nucleation, reducing dislocations, and improving the performance and reliability of the material.

[0143] By precisely using and decomposing TDMAS, this method achieves uniform and stable n-type doping, overcoming the problem of controlled doping concentration in traditional doping techniques, and effectively avoiding the formation of byproducts such as SiNx.

[0144] The precise control of growth conditions and optimization of gas flow reduce unnecessary raw material consumption and energy waste, significantly lowering production costs and improving the economic efficiency and environmental friendliness of SiC epitaxial wafer manufacturing.

[0145] By controlling the growth temperature, pressure, gas flow rate, and molar ratio, this method improves the stability and repeatability of the epitaxial growth process, ensuring consistency and controllability in mass production.

[0146] In existing technologies, TDMAS has not been chosen as a traditional silicon carbide epitaxial doping source, primarily due to its thermal stability and the complexity of its decomposition pathway. At high temperatures, it decomposes into dimethylamine radicals and silane derivatives, and its organic groups (-N(CH3)2) may produce carbon residues, contaminating the SiC epitaxial layer. Decomposition byproducts (such as carbon-containing gaseous substances) may react with the Si / H / C system to form amorphous carbon or other impurities. Furthermore, compared to direct gas-phase doping (such as N2), TDMAS needs to be carried from the bubbler by a carrier gas (H2), while the evaporation stability of liquid sources is significantly affected by temperature / pressure fluctuations, requiring precise control of the bubbler outlet concentration.

[0147] To address the aforementioned issues, this application employs a low-pressure environment to suppress side reactions, utilizing a 50 mbar low-pressure reaction chamber to significantly reduce the TDMAS gas-phase residence time, preventing the carbonization of organic groups. Furthermore, it employs "temperature-coordinated optimization," using 1550℃ pre-etching to remove surface oxygen (preventing Si-O bond interference with doping), and a 1625℃ growth temperature to promote the complete decomposition of TDMAS into Si-N bonds, with organic groups reduced by H2 to volatile CH4 / NH3. This resolves the issue of potential impurities in the products during the TDMAS decomposition process. Additionally, by progressively reducing the H2 flow rate from 160 slm to 100 slm, gas-phase nucleation is suppressed while maintaining uniform TDMAS transport. To address the issue of the stability of liquid source evaporation being affected by temperature / pressure fluctuations, the hydrogen flow rate delivered to the bubbler in this application must be strictly within the 80-120 sccm window, while the bubbler temperature is controlled at 35-45℃. If the flow rate is too low (<80 sccm), the concentration at the bubbler outlet will be too high, which will easily cause condensation in the pipeline; if it is too high (>120 sccm), the partial pressure of TDMAS will decrease, and the doping efficiency will drop sharply. Temperature control is mainly because if the temperature in the pipeline entering the high-temperature reaction chamber is not properly controlled or there is local overheating, TDMAS may decompose prematurely or undergo side reactions, leading to pipeline blockage, unstable doping efficiency, or introduction of contamination.

[0148] This application uses TDMAS as the n-type dopant source because TDMAS can decompose at relatively low temperatures (150℃~300℃), which is lower than the formation temperature of silicon carbide (1500℃~1700℃), resulting in higher decomposition efficiency and significantly reducing the need for high temperatures. This not only improves doping efficiency but also reduces energy consumption. By generating TDMAS under a low-pressure environment of 50 Mbr, the residence time of TDMAS in the reaction chamber is significantly shortened, effectively avoiding the residue and memory effect of gaseous dopants, thus ensuring uniformity and stability during the doping process, and further improving the uniform doping quality of the epitaxial wafer. The organic groups after TDMAS decomposition are reduced to volatiles in the H2 environment. The process avoids the formation of byproducts such as volatile CH4 and NH2, rather than impurities such as SiNx. Furthermore, pre-etching at 1550℃ removes surface oxygen, and the complete decomposition of TDMAS at a growth temperature of 1625℃ ensures that the decomposition products do not react with SiC growth to produce byproducts. This significantly improves the crystal quality and purity of the SiC epitaxial wafer. This application achieves precise control of doping concentration by accurately controlling the evaporation and carrying of TDMAS, combined with optimized growth conditions. TDMAS not only provides N atoms for n-type doping but also provides Si atoms to participate in SiC lattice growth, optimizing the C / Si ratio, avoiding the formation of SiNx, and ensuring efficient utilization of the dopant and stability of the doping concentration.

[0149] By gradually reducing the H2 flow rate from 160 slm to 100 slm and controlling the TDMAS-carrying flow rate within the range of 80 sccm-120 sccm, uniform transport and complete decomposition of TDMAS were ensured, while gas-phase nucleation was suppressed, maintaining a stable supply of carbon and silicon sources. This overcame the problem caused by the high flow rate requirement of dopants. Furthermore, by increasing the carbon source gas to the range of 300-600 sccm and reducing the H2 flow rate to 85 slm, the optimal C / Si ratio was maintained within the range of 0.9-1.2. This effectively uniformly promoted the nucleation of impurity crystal forms, optimized the crystal structure of SiC epitaxial wafers, and overcame the problem of by-product formation.

[0150] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0151] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0152] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0153] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0154] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0155] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for growing silicon carbide epitaxial wafers, characterized in that, include: With initial pressure and initial temperature in the reaction chamber, a silicon carbide substrate is transferred into the reaction chamber, and hydrogen gas is supplied into the reaction chamber. The reaction chamber is subjected to heating and depressurization operations to perform in-situ etching of the silicon carbide substrate; The reaction chamber is heated and depressurized, while the flow rate of hydrogen is reduced. A carbon source and a silicon source are introduced into the reaction chamber, and the hydrogen is used to carry tris(dimethylamino)silane into the reaction chamber for buffer layer growth. Increase the flow rate of the carbon source into the reaction chamber and decrease the flow rate of the hydrogen gas to grow the main epitaxial layer; After epitaxial growth is complete, the reaction gas is turned off, the temperature is lowered and the pressure is increased, and the silicon carbide epitaxial wafer is removed.

2. The method for growing silicon carbide epitaxial wafers according to claim 1, characterized in that, The initial pressure is between 800 mbar and 1200 mbar, preferably 1000 mbar; and / or the initial temperature is between 600°C and 900°C, preferably 800°C; and / or the flow rate of hydrogen supplied to the reaction chamber is between 120 slm and 200 slm, preferably 160 slm.

3. The method for growing silicon carbide epitaxial wafers according to claim 1, characterized in that, During the heating and depressurization operation of the reaction chamber, the first target temperature of the reaction chamber is between 1450°C and 1650°C, preferably 1550°C; the first target pressure of the reaction chamber is between 100 mbar and 150 mbar, preferably 120 mbar. After the real-time temperature and pressure of the reaction chamber reach the first target temperature and the real-time pressure of the reaction chamber reach the first target pressure, the pressure is maintained for a set time of 12 min to 18 min, preferably 15 min, to perform in-situ etching of the silicon carbide substrate.

4. The method for growing silicon carbide epitaxial wafers according to claim 1, characterized in that, During the process of heating the reaction chamber, the heating time of the reaction chamber is 10 minutes.

5. The method for growing silicon carbide epitaxial wafers according to claim 1, characterized in that, During the heating and depressurization operation of the reaction chamber, the second target temperature of the reaction chamber is between 1600℃ and 1650℃, preferably 1625℃; and / or, the temperature rise rate of the reaction chamber from the first target temperature to the second target temperature is between 8℃ / min and 15℃ / min, preferably 10℃ / min.

6. The method for growing silicon carbide epitaxial wafers according to claim 1, characterized in that, During the process of heating and depressurizing the reaction chamber while reducing the flow rate of hydrogen, the flow rate of hydrogen is reduced to between 90 slm and 120 slm, preferably 100 slm; the pressure of the reaction chamber is reduced from the first target pressure to between 40 mbar and 60 mbar, preferably 50 mbar.

7. The method for growing silicon carbide epitaxial wafers according to claim 1, characterized in that, During the process of introducing a carbon source and a silicon source into the reaction chamber, the carbon source is ethylene and the silicon source is trichlorosilane; and / or, the carbon source gas flow rate is 60 sccm to 90 sccm, preferably 85 sccm; and / or, the molar ratio of the introduced carbon source to the introduced silicon source is 0.9:1.2, preferably 1.

0.

8. The method for growing silicon carbide epitaxial wafers according to claim 1, characterized in that, In the process of using hydrogen to carry tris(dimethylamino)silane into the reaction chamber, the hydrogen is used to store the tris(dimethylamino)silane in a bubbler, and the temperature of the bubbler is controlled between 35°C and 45°C. The hydrogen is controlled to be input into the bubbler at a set flow rate, carrying the tris(dimethylamino)silane into the reaction chamber; wherein, the set flow rate is 80 sccm to 120 sccm, preferably, the set flow rate is 100 sccm.

9. The method for growing silicon carbide epitaxial wafers according to claim 1, characterized in that, During the process of increasing the flow rate of the carbon source into the reaction chamber and decreasing the flow rate of the hydrogen, the flow rate of the carbon source is controlled to increase from 60 sccm to 90 sccm to 300-600 sccm, preferably 510 sccm, while the molar ratio of the carbon source to the silicon source remains unchanged, and the flow rate of the hydrogen is reduced to between 70 slm and 90 slm, preferably 85 slm.

10. A silicon carbide epitaxial wafer, characterized in that, The silicon carbide epitaxial wafer is prepared by the growth method of the silicon carbide epitaxial wafer according to any one of claims 1 to 9.

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