Growth method for P-type heavy doping chemical potential regulation of 4H-SiC
By periodically switching C-rich and Si-rich atmospheres, the problems of lattice distortion and low doping efficiency in the growth of P-type heavily doped 4H-SiC epitaxial layer are solved, and efficient, uniform doping and rapid growth are achieved .
Patent Information
- Application Number
- CN202411336816.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-24
- Publication Date
- 2025-01-03
AI Technical Summary
The growth quality control of the P-type heavily doped 4H-SiC epitaxial layer is difficult, especially in large sizes, Al doping efficiency decreases, and lattice structure distortion caused by P-type doped atoms affects device performance.
The periodically switched C-rich atmosphere and Si-rich atmosphere are used to grow the P-type heavily doped 4H-SiC epitaxial layer. The adsorption formation energy of P-type doped atoms is reduced through the C-rich atmosphere, the adsorption intensity is improved, and the Si-rich atmosphere is in the Si-rich atmosphere. The bonding ability of doped atoms and SiC crystals is enhanced, and the growth rate and efficiency are improved.
It realizes efficient adsorption and effective bonding of P-type doped atoms, reduces lattice structure distortion, improves the growth quality and doping efficiency of the 4H-SiC epitaxial layer, and meets the needs of high concentration doping and fast and uniform growth.
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Figure CN119243328A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of SiC epitaxial technology, and more specifically, to a growth method of 4H-SiC with P-type heavily doped chemical potential regulation. Background Art
[0002] Silicon carbide (SiC) semiconductor materials are widely used in power devices due to their advantages such as high electron mobility, high thermal conductivity and wide bandgap. In recent years, with the vigorous development of new energy vehicles and other fields, the silicon carbide industry has ushered in new opportunities. The doping type and concentration of the epitaxial layer are a key factor in determining the performance of silicon carbide devices. N-type doped 4H-SiC epitaxial technology has made significant progress, and high-concentration uniform doping can be achieved at a large size of 150 mm. However. The growth quality control of heavily P-type doped 4H-SiC still faces many technical bottlenecks and challenges.
[0003] At present, due to their large atomic radius, P-type doping atoms are prone to cause lattice structure distortion during the doping process, which in turn affects the quality of P-type heavily doped 4H-SiC epitaxial layers. What is more complicated is that under large-scale growth conditions, the doping efficiency of Al shows a significant downward trend. Summary of the invention
[0004] In view of this, the present application provides a growth method of 4H-SiC with P-type heavy doping chemical potential regulation, the scheme is as follows:
[0005] A growth method of 4H-SiC with P-type heavy doping chemical potential regulation, comprising:
[0006] Providing SiC substrate;
[0007] Pre-treating the SiC substrate;
[0008] Source gas is introduced to grow a P-type heavily doped 4H-SiC epitaxial layer on the surface of a pretreated SiC substrate; the source gas includes: a C source gas, a Si source gas and a P-type doping source gas; during the growth of the 4H-SiC epitaxial layer, the 4H-SiC epitaxial layer is grown from a C-rich atmosphere, and the SiC substrate is periodically in a C-rich atmosphere and a Si-rich atmosphere; the C-rich atmosphere is used to reduce the adsorption formation energy of the P-type doping atoms and improve the adsorption strength of the 4H-SiC epitaxial layer on the surface of the SiC substrate; the Si-rich atmosphere is used to enhance the bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules and improve the growth rate of the 4H-SiC epitaxial layer.
[0009] Optionally, in the above growth method, the growth process of the 4H-SiC epitaxial layer includes multiple growth cycles, and the growth cycle includes a first stage in a C-rich atmosphere and a second stage in a Si-rich atmosphere;
[0010] The sum of the durations of the first stage and the second stage is equal to the duration of the growth cycle, and the duration of the first stage is greater than the duration of the second stage.
[0011] Optionally, in the above growth method, in the same growth cycle, the ratio of the duration of the first stage to the duration of the second stage is greater than 3 and less than 10.
[0012] Optionally, in the above growth method, in a C-rich atmosphere, the P-type doping source gas is introduced at a fixed flow rate, and in a Si-rich atmosphere, the introduction of the P-type doping source gas is stopped.
[0013] Optionally, in the above growth method, in a C-rich atmosphere, the chemical potential of the C element Greater than -9.300000 eV and less than -9.095729 eV;
[0014] In Si-rich atmosphere, the chemical potential of Si element Greater than -5.742799 eV and less than -5.419999 eV.
[0015] Optionally, in the above growth method, in a C-rich atmosphere, the ratio of C atoms to Si atoms is greater than 1 and not greater than 2;
[0016] In a Si-rich atmosphere, the ratio of C atoms to Si atoms is not less than 0.5 and less than 1.
[0017] Optionally, in the above growth method, during the growth of the 4H-SiC epitaxial layer, the flow rate of one of the C source gas and the Si source gas is constant, and the flow rate of the other can be switched between a first flow rate and a second flow rate to achieve switching between a C-rich atmosphere and a Si-rich atmosphere;
[0018] The first flow rate is not equal to the second flow rate; and the switching duration between the first flow rate and the second flow rate is shorter than the duration of the first flow rate and the duration of the second flow rate.
[0019] Optionally, in the above growth method, the SiC substrate has an offset angle of 4° to 8° along the <11-20> direction on the (0001) crystal plane of the SiC crystal.
[0020] Optionally, in the above growth method, the method of pretreating the SiC substrate includes:
[0021] After the growth chamber is heated and pressurized, the surface of the SiC substrate is etched to eliminate damage on the surface of the SiC substrate;
[0022] During the pretreatment process, the growth chamber has a first pressure and a first temperature; during the growth of the 4H-SiC epitaxial layer, the growth chamber has a second pressure and a second temperature; the first pressure is greater than the second pressure, and the first temperature is greater than the second temperature.
[0023] Optionally, in the above growth method, during the growth of the 4H-SiC epitaxial layer, the temperature in the growth chamber ranges from 1500° C. to 1700° C.; and the growth pressure ranges from 80 mbar to 150 mbar.
[0024] It can be known from the above description that in the growth method of 4H-SiC P-type heavily doped chemical potential regulation provided by the technical solution of the present application, the growth of the P-type heavily doped 4H-SiC epitaxial layer is carried out based on the periodically switched C-rich atmosphere and Si-rich atmosphere. In the growth process of the 4H-SiC epitaxial layer, the growth of the 4H-SiC epitaxial layer starts from the C-rich atmosphere. In the C-rich atmosphere, the adsorption formation energy of the P-type doping atoms can be effectively reduced, the efficient adsorption of the P-type doping atoms can be achieved, the adsorption strength of the 4H-SiC epitaxial layer on the surface of the SiC substrate can be improved, and the distortion problem of the lattice structure caused by the P-type doping atoms can be reduced; in the Si-rich atmosphere, by supplementing the Si source, the bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules can be further enhanced, making it difficult to desorb, thereby achieving effective doping and improving the doping efficiency, and the chemical potential balance in the growth chamber can be regulated in the Si-rich atmosphere, which can increase the growth rate of the 4H-SiC epitaxial layer. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.
[0026] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which this application can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by this application, should still fall within the scope of the technical contents disclosed in this application.
[0027] Figure 1 A schematic diagram of a growth method of 4H-SiC P-type heavily doped chemical potential regulated according to an embodiment of the present application;
[0028] Figure 2A schematic diagram of the flow rates of various gases in a 4H-SiC epitaxial growth process provided in an embodiment of the present application;
[0029] Figure 3 A schematic diagram of a process flow of another 4H-SiC P-type heavily doped chemical potential controlled growth method provided in an embodiment of the present application;
[0030] Figure 4 It is the adsorption energy curve under C-rich atmosphere;
[0031] Figure 5 The diffusion path and energy diagram of Al atoms near the step in C-rich atmosphere;
[0032] Figure 6 The relationship between the formation energy of different clusters adsorbed on the two step boundaries and the chemical potential of Si element;
[0033] Figure 7 It is the adsorption energy curve in Si-rich atmosphere in the control experiment;
[0034] Figure 8 This is the diffusion path and energy diagram of Al atoms near the step in the control experiment. DETAILED DESCRIPTION
[0035] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the embodiments in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.
[0036] During the growth of P-type doped 4H-SiC epitaxial layer, trimethylaluminum (TMA) is often used as a precursor. Although this precursor can effectively introduce Al atoms as P-type doping atoms, as described in the background technology, Al atoms are prone to cause lattice structure distortion during the doping process due to their large atomic radius, thereby affecting the quality of the P-type heavily doped 4H-SiC epitaxial layer. What is more complicated is that under large-scale growth conditions, the doping efficiency of Al shows a significant downward trend.
[0037] Chemical vapor deposition (CVD) technology has become the mainstream method for growing 4H-SiC epitaxial layers due to its unique advantages in epitaxial layer surface flatness and large-area uniform doping. Under this technical framework, precise control of the flow rates of C source gas and Si source gas is crucial to the micromorphology and doping efficiency of 4H-SiC epitaxy. The synchronous deposition of C atoms and Si atoms promotes high-quality film growth, while the competitive deposition of Al atoms and Si atoms directly affects the doping efficiency. Therefore, precise control of the C / Si stoichiometric ratio (the ratio of the number of C atoms to Si atoms) in the source gas during epitaxy has become a key factor in optimizing the quality of epitaxial growth and improving doping efficiency.
[0038] In the growth process of 4H-SiC epitaxial layer, in order to maintain the stability of the growth process, a fixed C / Si stoichiometric ratio is often used for growth. This fixed C / Si stoichiometric ratio can achieve both growth uniformity and doping concentration uniformity within a small range, but the effect of the C / Si stoichiometric ratio on the growth quality of epitaxial wafers is two-sided. For example, when the C / Si stoichiometric ratio is higher than 0.85, it is conducive to achieving doping uniformity, while when it is lower than 1, it can reduce the defects of the epitaxial layer and improve the surface quality. Although the increase in the C / Si stoichiometric ratio helps to increase the doping concentration of Al atoms, an excessively high C / Si stoichiometric ratio may damage the quality of the epitaxial wafer.
[0039] Based on the above description, it can be seen that how to ensure the high doping concentration of large-size 4H-SiC epitaxial layer while maintaining the excellent growth quality of the 4H-SiC epitaxial layer has become a difficult problem that needs to be solved in P-type 4H-SiC doping technology. At present, there is no solution in the industry that combines the advantages of different C / Si stoichiometric ratios on epitaxial growth while avoiding its potential negative effects.
[0040] In view of this, an embodiment of the present application provides a growth method of 4H-SiC with P-type heavy doping chemical potential regulation, comprising:
[0041] Providing SiC substrate;
[0042] Pre-treating the SiC substrate;
[0043] Source gas is introduced to grow a P-type heavily doped 4H-SiC epitaxial layer on the surface of a pretreated SiC substrate; the source gas includes: a C source gas, a Si source gas and a P-type doping source gas; during the growth of the 4H-SiC epitaxial layer, the 4H-SiC epitaxial layer is grown from a C-rich atmosphere, and the SiC substrate is periodically in a C-rich atmosphere and a Si-rich atmosphere; the C-rich atmosphere is used to reduce the adsorption formation energy of the P-type doping atoms and improve the adsorption strength of the 4H-SiC epitaxial layer on the surface of the SiC substrate; the Si-rich atmosphere is used to enhance the bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules and improve the growth rate of the 4H-SiC epitaxial layer.
[0044] In a C-rich atmosphere, the C / Si stoichiometric ratio is greater than 1, and in a Si-rich atmosphere, the C / Si stoichiometric ratio is less than 1.
[0045] During the growth process of the 4H-SiC epitaxial layer, the growth of the 4H-SiC epitaxial layer is started from a C-rich atmosphere. In the C-rich atmosphere, the adsorption formation energy of the P-type doping atoms can be effectively reduced, and the efficient adsorption of the P-type doping atoms can be achieved. The adsorption strength of the 4H-SiC epitaxial layer on the surface of the SiC substrate can be improved, and the distortion problem of the lattice structure caused by the P-type doping atoms can be reduced. In the Si-rich atmosphere, by supplementing the Si source, the bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules can be further enhanced, making it difficult to desorb, thereby achieving effective doping and improving the doping efficiency. In addition, the chemical potential balance in the growth chamber can be regulated in the Si-rich atmosphere, which can increase the growth rate of the 4H-SiC epitaxial layer.
[0046] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0047] refer to Figure 1 , Figure 1 A schematic flow chart of a growth method of 4H-SiC P-type heavily doped chemical potential regulated growth provided in an embodiment of the present application, wherein the growth method comprises:
[0048] Step S11: providing a SiC substrate;
[0049] Step S12: pre-treating the SiC substrate;
[0050] Step S13: introducing source gas to grow a P-type heavily doped 4H-SiC epitaxial layer on the surface of the pretreated SiC substrate; the source gas includes: a C source gas, a Si source gas and a P-type doping source gas; during the growth of the 4H-SiC epitaxial layer, the 4H-SiC epitaxial layer is grown from a C-rich atmosphere, and the SiC substrate is periodically in a C-rich atmosphere and a Si-rich atmosphere; the C-rich atmosphere is used to reduce the adsorption formation energy of the P-type doping atoms and improve the adsorption strength of the 4H-SiC epitaxial layer on the surface of the SiC substrate; the Si-rich atmosphere is used to enhance the bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules, thereby increasing the growth rate of the 4H-SiC epitaxial layer.
[0051] In the embodiment of the present application, the P-type doping source gas is TMA as an example for explanation, and TMA can provide Al atoms as P-type doping atoms. The P-type doping atoms in the P-type doping source gas may include any one of boron (B) atoms, gallium (Ga) atoms, indium (In) atoms, and aluminum (Al), and are not limited to Al atoms. The P-type doping source is not limited to TMA, and the desired P-type doping source can be selected according to the element type of the P-type doping atom.
[0052] During the growth process of the 4H-SiC epitaxial layer, the growth of the 4H-SiC epitaxial layer is started from a C-rich atmosphere. In the C-rich atmosphere, the adsorption formation energy of the P-type doping atoms can be effectively reduced, and the efficient adsorption of the P-type doping atoms can be achieved. The adsorption strength of the 4H-SiC epitaxial layer on the surface of the SiC substrate can be improved, and the distortion problem of the lattice structure caused by the P-type doping atoms can be reduced. In the Si-rich atmosphere, by supplementing the Si source, the bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules can be further enhanced, making it difficult to desorb, thereby achieving effective doping and improving the doping efficiency. In addition, the chemical potential balance in the growth chamber can be regulated in the Si-rich atmosphere, which can increase the growth rate of the 4H-SiC epitaxial layer.
[0053] Optionally, the method for pretreating the SiC substrate includes: after heating and pressurizing the growth chamber, etching the surface of the SiC substrate to eliminate damage on the surface of the SiC substrate; wherein, during the pretreatment, the growth chamber has a first pressure and a first temperature; during the growth of the 4H-SiC epitaxial layer, the growth chamber has a second pressure and a second temperature; the first pressure is greater than the second pressure, and the first temperature is greater than the second temperature.
[0054] Among them, optionally, during the growth process of the 4H-SiC epitaxial layer, the second pressure can be 80 mbar ~150 mbar, and the second temperature can be 1500°C ~1700°C. Based on this temperature and pressure range, combined with the periodic growth process of the C-rich atmosphere and the Si-rich atmosphere in the embodiment of the present application, the rapid and uniform growth of the 4H-SiC epitaxial layer can be guaranteed, and the doping concentration can be guaranteed to meet the growth requirements.
[0055] The first temperature and the first pressure can be set under the condition of satisfying the etching process requirements. The embodiment of the present application does not limit the values of the first temperature and the first pressure.
[0056] Based on the pretreatment, the damage on the surface of the SiC substrate can be eliminated to provide a good growth surface for the 4H-SiC epitaxial layer and ensure the growth quality of the 4H-SiC epitaxial layer.
[0057] In the pretreatment stage, a carrier gas and an etching gas may be introduced into the growth chamber at the same time to perform etching on the surface of the SiC substrate at a first pressure and a first temperature. The carrier gas may include H2, and the etching gas may include H 2、 HCl, etc.
[0058] Optionally, the flow rate of the carrier gas can be constant throughout the entire process. If H2 is used as the carrier gas, the flow rate can be 50 slm to 150 slm. The etching time can be 3 min to 5 min. The flow rates of the carrier gas and the etching gas and the etching time can be limited according to the process requirements, and the embodiments of the present application do not limit this.
[0059] In the embodiment of the present application, the first pressure is set to be greater than the second pressure, and the first temperature is set to be greater than the second temperature, so that a higher temperature and pressure can be achieved during the etching process, which facilitates faster etching of the SiC substrate surface to increase the pretreatment speed.
[0060] In addition, since the first pressure is greater than the second pressure and the first temperature is greater than the second temperature, the temperature and pressure during the epitaxial growth process can be relatively low. Therefore, after the pre-treatment etching is completed and before the epitaxial growth, it is necessary to pre-introduce the source gas to exhaust the etching gas in the growth chamber before the first cycle begins. The source gas introduced during the exhaust time period can also be used to reduce the pressure and temperature in the growth chamber to the temperature and pressure required to meet the 4H-SiC epitaxial layer, without the need for separate cooling and pressure reduction time.
[0061] Alternatively, after the etching process is completed, the temperature in the growth chamber may be adjusted to the second temperature and the second pressure, and then the carrier gas and the source gas required for epitaxial growth may be introduced.
[0062] Alternatively, in order to facilitate the pressure and temperature control of the growth chamber, the same pressure and temperature parameters may be used in the growth chamber during the pretreatment process and the growth process of the 4H-SiC epitaxial layer.
[0063] In the embodiment of the present application, the growth process of the 4H-SiC epitaxial layer includes multiple growth cycles, and the growth cycle includes a first stage in a C-rich atmosphere and a second stage in a Si-rich atmosphere; wherein the sum of the durations of the first stage and the second stage is equal to the duration of the growth cycle, and the duration of the first stage is greater than the duration of the second stage. The duration of the first stage is set to T1, the duration of the second stage is set to T2, the duration of a growth cycle is set to T0, T1+T2=T0, and T1>T2.
[0064] In the same cycle, since T1>T2, P-type doping atoms can be adsorbed in the first stage with a larger time proportion to ensure the doping concentration, and the bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules can be enhanced through the second stage with a smaller time proportion, making it difficult to desorb, thereby achieving effective doping.
[0065] A 4H-SiC epitaxial layer is formed on a SiC substrate based on periodically switching between a C-rich atmosphere and a Si-rich atmosphere, and the preparation of a highly doped 4H-SiC epitaxial layer can be achieved. A P-type heavily doped 4H-SiC epitaxial layer can be formed on a SiC substrate, and a high-rate growth rate of the 4H-SiC epitaxial layer can be maintained. While maintaining a high doping concentration, the rapid and uniform growth of the 4H-SiC epitaxial layer can be achieved.
[0066] As mentioned above, in a C-rich atmosphere, the adsorption formation energy of P-type doping atoms can be effectively reduced, and efficient adsorption of P-type doping atoms can be achieved, thereby achieving the growth of a 4H-SiC epitaxial layer with a high doping concentration. In addition, since T1>T2, a larger proportion of the time in a growth cycle can be used to achieve efficient adsorption of P-type doping atoms to ensure the quality of P-type heavy doping.
[0067] In one implementation of the present application, in the same growth cycle, the ratio of the duration T1 of the first stage to the duration T2 of the second stage is greater than 3 and less than 10, that is, .
[0068] exist When the value of T1 / T2 is adjusted, it can adapt the value of T1 / T2 to the periodic growth process of the 4H-SiC epitaxial layer, and ensure that the P-type doping atoms in the 4H-SiC epitaxial layer have a high doping concentration and realize P-type heavy doping. At the same time, it can also ensure the doping efficiency of the P-type doping atoms and the growth rate of the 4H-SiC epitaxial layer, and can effectively reduce crystal defects.
[0069] Optionally, in a C-rich atmosphere, a P-type doping source gas is introduced at a fixed flow rate, and in a Si-rich atmosphere, the introduction of the P-type doping source gas is stopped. In the same cycle, the P-type doping atoms can be adsorbed in the first stage with a larger time proportion, which can not only meet the P-type atom doping in the first stage, but also can be used for the P-type atom doping in the second stage, and the doping concentration of the entire cycle can be guaranteed. The bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules is enhanced through the second stage with a smaller time proportion, making it difficult to desorb, thereby achieving effective doping. Among them, the second stage can also further adsorb P-type doping atoms based on the P-type doping source gas introduced into the growth chamber.
[0070] In other embodiments, the P-type doping source gas may be continuously introduced during the growth of the 4H-SiC epitaxial layer. In this method, the same flow rate of the P-type doping source gas is introduced in both the first stage and the second stage.
[0071] when When the ratio of T1 / T2 is too small, the ratio will be too short, which will cause T1 to be too short and unable to adsorb enough P-type doping atoms, thus resulting in the inability to meet the doping concentration requirement of P-type heavy doping. The ratio can also be kept at a moderate value, so as to avoid the ratio being too large, which will cause T2 to be too short and unable to effectively enhance the bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules, thus resulting in the inability to form effective doping.
[0072] During the growth of the 4H-SiC epitaxial layer, the flow rate of one of the C source gas and the Si source gas is constant, and the flow rate of the other can be switched between the first flow rate V1 and the second flow rate V2 to achieve the switching between the C-rich atmosphere and the Si-rich atmosphere; wherein the first flow rate V1 is not equal to the second flow rate V2, that is, V1≠V2; the switching time between the first flow rate V1 and the second flow rate V2 is less than the duration of the first flow rate V1 and the duration of the second flow rate V2. In this way, by keeping the flow rate of one of the C source gas and the Si source gas constant and the other switching between the first flow rate V1 and the second flow rate V2, the C / Si stoichiometric ratio in the growth chamber can be accurately controlled. If the C / Si stoichiometric ratio is greater than 1, it is in a C-rich atmosphere, and if the C / Si stoichiometric ratio is less than 1, it is in a Si-rich atmosphere. In this way, by controlling the flow rate change of one source gas, the periodic switching between the C-rich atmosphere and the Si-rich atmosphere can be achieved, which makes the source gas control method simple and reduces the process difficulty.
[0073] During the growth of the 4H-SiC epitaxial layer, the flow rate of the Si source gas can be set to a fixed third flow rate V3, and the value of V3 is between V1 and V2. For example, V1>V3>V2 can be set. At this time, the flow rates of various gases during the 4H-SiC epitaxial growth process can be as follows: Figure 2 shown.
[0074] refer to Figure 2 , Figure 2 A schematic diagram of the flow rates of various gases in a 4H-SiC epitaxial growth process provided in an embodiment of the present application, Figure 2 The horizontal axis is time, and the vertical axis is gas flow. In the time period T3 before the first growth cycle, it is necessary to start to continuously introduce carrier gas and etching gas to pre-treat the surface of the SiC substrate and remove surface damage. During the growth process of the 4H-SiC epitaxial layer, Figure 2 The C source gas, Si source gas and P-type doping source gas are introduced in sequence. In the subsequent growth process of the 4H-SiC epitaxial layer, multiple growth cycles are included, each of which lasts for T0, and each growth cycle includes a first stage lasting for T1 and a second stage lasting for T2, and the first stage is located before the second stage. If T1 is greater than T2, it can be further defined as .
[0075] like Figure 2 As shown, after the pretreatment lasting T3, the first growth cycle begins to start 4H-SiC epitaxial growth. During the 4H-SiC epitaxial growth process, the flow rate of the carrier gas is fixed at V5, and the flow rate of the Si source gas is fixed at V3. Since V1>V3>V2, in the first stage lasting T1, the C / Si stoichiometric ratio is greater than 1, which is a C-rich range; in the second stage lasting T2, the C / Si stoichiometric ratio is less than 1, which is a Si-rich atmosphere.
[0076] Wherein, V4 is greater than V1 to ensure that there are more P-type doping atoms in the growth chamber under a C-rich atmosphere, so as to adsorb enough P-type doping atoms to ensure the doping concentration. Optionally, V5 is greater than V4 to better carry various source gases into the growth chamber through the carrier gas.
[0077] exist Figure 2 In the method, the Si source gas is taken as an example to be continuously maintained during the growth process. Obviously, in other methods, the flow rate of the C source gas can also be fixed and the flow rate of the Si source gas can be switched to achieve periodic switching of the C-rich atmosphere and the Si-rich atmosphere during the growth process.
[0078] During the growth process of the 4H-SiC epitaxial layer, the SiC substrate is periodically in a C-rich atmosphere and a Si-rich atmosphere. By alternating between the C-rich atmosphere and the Si-rich atmosphere, the chemical potential of the C element and the chemical potential of the Si element in the growth chamber can be controlled to meet the growth requirements of the P-type heavily doped 4H-SiC epitaxial layer, and the uniform and rapid growth of the 4H-SiC epitaxial layer with the doping concentration meeting the requirements can be achieved.
[0079] In one embodiment, the P-type doping source gas may be TMA, the C source gas may be C2H4, and the Si source gas may be SiH4. In a C-rich atmosphere, the C / Si stoichiometric ratio is greater than 1, the C2H4 flow rate may be 20 sccm, and the SiH4 flow rate is less than 40 sccm; in a Si-rich atmosphere, the C / Si stoichiometric ratio is less than 1, the C2H4 flow rate is continuously maintained at 20 sccm, and the SiH4 flow rate is greater than 40 sccm. In this method, whether it is a C-rich atmosphere or a Si-rich atmosphere, the TMA flow rate is maintained at 200 sccm.
[0080] In the embodiment of the present application, the C source gas, Si source gas and P-type doping source gas in the source gas can be selected based on the requirements. For example, the C source gas can be at least one of C3H8 and C2H4. The Si source gas can be at least one of SiH4 and TCS (trichlorosilane). The P-type doping source gas can be TMA.
[0081] In order to facilitate the control of the C / Si stoichiometric ratio in the growth chamber and the control of the gas flow rate, so as to more accurately control the chemical potential of the C element and the Si element in the reaction chamber, the C source gas, the Si source gas and the P-type doping source gas can be set to be a single gas. For example, the C source gas can be one of C3H8 and C2H4, and the Si source gas can be one of SiH4 and TCS (trichlorosilane).
[0082] In the growth method provided in the embodiment of the present application, in the C-rich atmosphere and the Si-rich atmosphere, the C / Si stoichiometric ratio can be precisely controlled by precisely controlling the flow rate, respectively, to precisely control the chemical potential of the C element and the Si element in the growth chamber. In the C-rich atmosphere, the chemical potential of the C element Greater than -9.300000 eV and less than -9.095729 eV; in a Si-rich atmosphere, the chemical potential of Si element Greater than -5.742799 eV and less than -5.419999 eV.
[0083] In a C-rich atmosphere, if the chemical potential of C element Greater than -9.300000 eV and less than -9.095729 eV. Further, the chemical potential of the C element is set by controlling the source gas flow rate. When the value is greater than -9.200000 eV and less than -9.100000 eV, the adsorption formation energy of P-type doping atoms can be effectively reduced, the efficient adsorption of P-type doping atoms can be achieved, and the adsorption strength of the 4H-SiC epitaxial layer on the surface of the SiC substrate can be improved.
[0084] In a Si-rich atmosphere, if the chemical potential of Si element Greater than -5.742799 eV and less than -5.419999 eV. Further, the chemical potential of the Si element is set by controlling the source gas flow rate. When it is greater than -5.600000 eV and less than -5.300000 eV, the bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules can be effectively enhanced, making it difficult for them to desorb, thereby achieving effective doping and improving the doping efficiency.
[0085] Optionally, in a C-rich atmosphere, the ratio of C atoms to Si atoms is greater than 1 and not greater than 2, so as to effectively reduce the adsorption formation energy of P-type doping atoms to a greater extent; in a Si-rich atmosphere, the ratio of C atoms to Si atoms is not less than 0.5 and less than 1, so as to enhance the bonding ability between the adsorbed P-type doping atoms and SiC crystal molecules to a greater extent.
[0086] In one implementation of the present application, the SiC substrate has an offset angle of 4° to 8° along the <11-20> direction on the (0001) crystal plane of the SiC crystal. Based on the SiC substrate with this offset angle, the surface of the substrate has an atomic step structure, which can promote the stable adsorption of atoms on the edge of the step, meet the step flow mode of epitaxial growth, and avoid the occurrence of high step bunching phenomenon, so as to obtain a 4H-SiC epitaxial layer with good surface uniformity.
[0087] From the above description, it can be seen that in the growth method provided in the embodiment of the present application, during the growth process of the P-type heavily doped 4H-SiC epitaxial layer, the growth of the P-type heavily doped 4H-SiC epitaxial layer is carried out by periodically switching the C-rich atmosphere and the Si-rich atmosphere. In the C-rich atmosphere, high-concentration growth of the 4H-SiC epitaxial layer can be achieved to meet the P-type heavy doping requirements, and in the Si-rich atmosphere, surface defects of the 4H-SiC epitaxial layer can be reduced.
[0088] Specifically, the growth process of the 4H-SiC epitaxial layer includes multiple growth cycles, and each growth cycle includes two growth stages. In the same growth cycle, in the first stage, based on the fine regulation of the flow rate of the C source gas and the flow rate of the Si gas, the growth chamber is placed in a C-rich atmosphere to achieve the growth of the 4H-SiC epitaxial layer with high concentration doping; in the second stage, by adjusting the gas flow rate so that the growth chamber is placed in a Si-rich atmosphere, the growth rate of the 4H-SiC epitaxial layer can be increased. At the same time, since the flow rate of the Si source gas is increased and the Si source gas is supplemented in the second stage, the chemical potential of the Si element and the C element in the growth chamber can be balanced, and the surface defects of the 4H-SiC epitaxial layer can be reduced, and the quality of the 4H-SiC epitaxial layer can be improved. Based on multiple of the above-mentioned cycle processes, SiC epitaxial wafers with high doping concentration and excellent flatness can be prepared, providing a solid material foundation for the subsequent semiconductor devices prepared based on the SiC epitaxial wafers.
[0089] The growth method provided in the embodiment of the present application is further described below in combination with specific source gases and process parameters.
[0090] refer to Figure 3 , Figure 3 A schematic flow chart of another method for growing 4H-SiC by P-type heavy doping chemical potential regulation provided in an embodiment of the present application, wherein the growth method includes:
[0091] Step S21: placing a SiC substrate in a growth chamber, and introducing an etching gas into the growth chamber based on a carrier gas to etch the SiC substrate to remove surface damage.
[0092] As mentioned above, the SiC substrate has an offset angle of 4° to 8° along the <11-20> direction on the (0001) crystal plane of the SiC crystal. In this step, the growth chamber can be controlled to be at a set first temperature and a first pressure to facilitate better etching processing.
[0093] The carrier gas may be H2. During the etching process, the flow rate of H2 may be 100 slm, and the etching time may be 3 to 5 minutes. Through the etching process, a regular step structure on the surface of the SiC substrate may be exposed. Optionally, the etching process may be performed at 1600°C, and the etching time may be 5 minutes.
[0094] Among them, the step structure is an atomic step structure formed by the SiC substrate on the (0001) crystal plane of the SiC crystal at an offset angle of 4°~8° along the <11-20> direction. Because there is a set offset angle between the substrate surface and the (0001) crystal plane, the substrate surface can have two steps with different atomic structures. The two different atomic step structures are defined as Step 1 and Step 2 respectively below.
[0095] Step S22: Adjust the temperature and pressure in the reaction chamber to meet the requirements of epitaxial growth. In this step, the reaction chamber may have a second pressure and a second temperature.
[0096] Step S23: introducing a carrier gas into the reaction chamber, and simultaneously introducing Si source gas, C source gas and Al source gas.
[0097] Optionally, the C source gas may be C2H4, the Si source gas may be SiH4, and the Al source gas may be TMA.
[0098] In order to control the growth environment, the flow rate of the C source gas can be periodically adjusted so that the growth chamber can be periodically switched between a C-rich atmosphere and a Si-rich atmosphere. The introduction of the Al source gas can be suspended in the Si-rich environment.
[0099] During the growth process, the growth chamber is periodically switched between a C-rich atmosphere and a Si-rich atmosphere. Each growth cycle includes a first stage and a second stage. The first stage and the second stage are regarded as a complete cycle. By repeating the cycle process, a 4H-SiC epitaxial layer can be prepared through multiple growth cycles, which can ensure precise control of the growth process and effective synthesis of the 4H-SiC epitaxial layer.
[0100] Step S24: After the growth is completed, the temperature is lowered and the epitaxial wafer is taken out. In this step, after the source gas and the carrier gas are turned off, the epitaxial wafer can be cooled naturally or actively cooled by introducing an inert gas before being taken out from the growth chamber.
[0101] In the growth method provided in the embodiment of the present application, a P-type heavily doped 4H-SiC epitaxial layer is prepared based on a periodically switched C-rich atmosphere and a Si-rich atmosphere. Based on the switching of the C-rich atmosphere and the Si-rich atmosphere, the chemical potential in the growth chamber can be precisely controlled to achieve high-concentration P-type doping and rapid and uniform growth of the 4H-SiC epitaxial layer.
[0102] The chemical potential can be controlled by controlling the flow rate of the source gas. In a C-rich atmosphere, Al atoms and SiC2 molecules can be preferentially adsorbed during the growth process. In a Si-rich atmosphere, the Si source is supplemented through technology to further enhance the bonding ability between the adsorbed Al atoms and the crystal molecules, making it difficult to desorb, thereby achieving effective doping.
[0103] In the process of growing a 4H-SiC epitaxial layer, the present application can grow a P-type doped 4H-SiC epitaxial layer by regulating the chemical potential, and the regulation of the chemical potential satisfies the following conditions:
[0104] (1)
[0105] In the above formula (1), It represents the change in the formation energy of various adsorbed clusters on the step edge of the SiC substrate relative to the clean step surface. It indicates the energy when Si, C and Al related atoms or clusters are adsorbed on the step edge. represents the energy of a clean step surface without additional adsorbed molecules, , as well as In each adsorption structure, the change of Si, C and Al atoms relative to the clean step is represented in turn. , as well as The elemental chemical potentials of Si, C and Al are represented in turn. Among them, the elemental chemical potential of Al can be determined by the fcc (face-centered cubic) structure. The elemental chemical potentials of Si and C satisfy the following conditions:
[0106] (2)
[0107] In the above equation (2) as the equilibrium condition, Represents the chemical potential of 4H-SiC crystal.
[0108] According to the above formula (1) and formula (2), we can Expressed as a formula that includes only one element's chemical potential variable, the formula is as follows:
[0109] (3)
[0110] In the above formula (3), the right side of the equal sign is is a variable, and the other parameters are constants that can be determined.
[0111] In addition, in order to avoid the formation of single crystal Si and C during the deposition process, the flow rate of the source gas is controlled so that the elemental chemical potential of Si and C satisfies:
[0112] (4)
[0113] (5)
[0114] in, It represents the formation enthalpy of SiC, which indicates the thermal effect of generating 1 mole of SiC from the most stable element at a certain temperature and pressure. , represents the chemical potential of a single C atom and a single Si atom in a diamond crystal and a silicon crystal, respectively. As mentioned above, in the embodiment of the present application, it is possible to control Greater than -5.742799 eV and less than -5.419999 eV, control Greater than -9.300000 eV and less than -9.095729 eV.
[0115] Based on the above formula, the adsorption energy of Al atoms and Si, C and other clusters simultaneously adsorbed in a C-rich atmosphere can be calculated: , and the adsorption energies of Al atoms and these clusters when adsorbed individually , , the adsorption energies are Figure 4 shown.
[0116] refer to Figure 4 , Figure 4 is the adsorption energy curve in C-rich atmosphere. The adsorption energy of Al atoms and SiC2 at the same time is The sum of their adsorption energies is .based on Figure 1 It can be seen that in a C-rich environment, the adsorption energy of Al atoms is significantly reduced, which is less than the sum of the energies of Al atoms and SiC2 adsorption respectively. This finding shows that in a C-rich atmosphere, Al atoms are more easily captured by substrate atoms and exist stably. This feature has significant advantages for achieving high-concentration doping because it reduces the energy barrier required in the doping process, allowing more Al atoms to be successfully doped into the epitaxial layer.
[0117] In the C-rich state, . Based on this calculation, the total adsorption energy of Al+SiC2 is -2.4086eV and -2.19966eV in Step 1 and Step 2, respectively. In contrast, the sum of the adsorption energy of a single Al atom and a single SiC2 cluster is -1.40086eV (corresponding to Step 1) and -1.48506eV (corresponding to Step 2), respectively, which is higher than the total adsorption energy of Al+SiC2. This comparison shows that the adsorption energy between Al atoms and SiC2 clusters is stronger in a C-rich atmosphere. When the growth chamber maintains a C-rich atmosphere, the adsorption of Al atoms is promoted, and high-concentration Al doping can be achieved.
[0118] In addition, the C-rich environment provides a more favorable adsorption site for the adsorption of Al atoms. The diffusion barrier of Al atoms near the step in the C-rich atmosphere can be calculated based on the transition state (Nudged Elastic Band, NEB), such as Figure 5 shown.
[0119] refer to Figure 5 , Figure 5 The diffusion path and energy diagram of Al atoms near the step in a C-rich atmosphere. Figure 5 The middle (a) figure shows the diffusion path and energy diagram near Step 1. Figure 5Figure (b) shows the diffusion path and energy diagram near Step 2. The C-rich environment provides a more superior adsorption site for Al adsorption. The energy barrier diagram is obtained with the distance from the edge position as the horizontal axis and the energy as the vertical axis. Specifically, the lowest adsorption energy of Al atoms is located at the edge of the step, and this feature makes it more inclined to adsorb at these positions. When Al atoms try to diffuse outward, they encounter higher potential barriers, which further confirms the phenomenon that Al atoms tend to be stably adsorbed at the edge of the step in a C-rich environment. This specific adsorption mode not only helps to maintain the step structure of the substrate, but also satisfies the step flow mode of epitaxial growth, effectively avoiding the clustering phenomenon of the step, thereby ensuring the uniformity and high quality of the surface.
[0120] When switching to Si-rich atmosphere, the introduction of Al source gas is suspended. The growth of P-type heavily doped 4H-SiC epitaxial layer is mainly driven by the adsorption and deposition of C and Si atoms. Therefore, the adsorption energy / formation energy of various atoms or clusters at the step edge is calculated as follows: Figure 6 shown.
[0121] refer to Figure 6 , Figure 6 This is a curve diagram showing the relationship between the formation energy of different clusters adsorbed on two step boundaries and the chemical potential of the Si element. Figure 6 The middle figure (a) shows the relationship between the formation energy of different clusters adsorbed at the Step 1 boundary and the Si chemical potential. Figure 6 Figure (a) shows the relationship between the formation energy of different clusters adsorbed at the Step 2 boundary and the Si chemical potential (b). At the two steps, the various adsorption energies obtained indicate that the Si-related clusters have lower energy than the C-related clusters. At the same time, in a Si-rich environment, the Si growth clusters can reach the lowest adsorption energy, and the epitaxial growth can have a higher growth rate. The step edge preferentially adsorbs Si2C clusters, and their adsorption energies are -2.9 eV (corresponding to Step 1) and -3.74 eV (corresponding to Step 2). Since the formation energy of Si-related clusters is lower than that of C-related clusters, according to the formation energy △E f Relationship with coverage θ:
[0122] (6)
[0123] In the above formula (6), T represents temperature, k represents Kelvin constant, and P represents pressure. The coverage of surface Si-related clusters is higher than that of C. Therefore, in order to achieve the balance of chemical potential in the growth chamber, the maintenance time of Si-rich atmosphere should be less than that of C-rich atmosphere, that is, in the same growth cycle, the duration of the second stage is less than that of the first stage. At the same time, in Si-rich atmosphere, the adsorption energy of Al atoms is higher than that in C-rich atmosphere. Therefore, in this growth stage, the introduction of Al doping source is suspended to avoid the influence of additional Al atoms on the growth process.
[0124] If other process conditions remain unchanged, Si source gas, C source gas and Al source gas are introduced simultaneously in Si-rich atmosphere and the flow rate is kept constant. In Si-rich atmosphere, the flow rate of Si source gas is greater than that of C source gas. Calculate the adsorption energy of Al atoms and Si, C and other clusters adsorbed simultaneously in Si-rich atmosphere. , and the adsorption energies of Al atoms and these clusters when adsorbed individually , , the adsorption energies are Figure 7 In a Si-rich atmosphere, the cluster of Si and C is represented by Si2C, and in a C-rich atmosphere, the cluster of Si and C is represented by SiC2.
[0125] refer to Figure 7 , Figure 7 This is the adsorption energy curve in the Si-rich atmosphere in the control experiment. . In a Si-rich atmosphere, the total adsorption energy of Al+Si2C is -4.16736 eV (corresponding to Step 1), -4.45548 eV (corresponding to Step 2). In comparison, the sum of the adsorption energy of a single Al atom and a single Si2C cluster is -4.65792 eV (corresponding to Step 1) and -5.38434 eV (Step 2), respectively. This result clearly shows that in a Si-rich atmosphere, the adsorption of Al atoms is not enhanced, but rather shows a weaker adsorption trend, which indicates that a Si-rich environment is not conducive to the adsorption of Al atoms, and it is difficult to obtain a P-type epitaxial wafer with a high doping concentration under this condition.
[0126] refer to Figure 8 , Figure 8 To compare the diffusion path and energy diagram of Al atoms near the step in the experimental example, Figure 8 The middle figure (a) shows the diffusion path and energy diagram near Step 1. Figure 8Figure (b) shows the diffusion path and energy diagram near Step 2. The adsorption energy of Al atoms at the step edge in the Si-rich state is relatively high, which means that its adsorption state is not stable enough. Under this condition, Al atoms tend to diffuse to the fcc site (corresponding to Step 1) and hcp (close-packed hexagonal lattice) site (corresponding to Step 2) away from the step edge. When too much Al is deposited on the step surface, it will affect the mobility of subsequent Si, C and other clusters, causing the occurrence of two-dimensional nucleation, increasing the surface roughness, and reducing the surface growth quality. Compared with the embodiment, it is difficult to obtain high-concentration, high-quality P-type 4H-SiC epitaxial wafers.
[0127] In the specification of this application, each embodiment is described in a progressive, parallel, or progressive and parallel manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. The implementation methods provided in the embodiments of this application can be combined with each other if there is no contradiction.
[0128] It should be noted that in the description of the present application, it should be understood that the description of the drawings and embodiments is illustrative rather than restrictive. The same reference numerals throughout the embodiments of the specification identify the same structure. In addition, for the sake of understanding and ease of description, the drawings may exaggerate the thickness of some layers, films, panels, regions, etc. It is also understood that when an element such as a layer, film, region, or substrate is referred to as "on" another element, the element may be directly on the other element or there may be an intermediate element. In addition, "on" refers to positioning an element on or below another element, but does not essentially refer to positioning on the upper side of another element according to the direction of gravity.
[0129] The terms "upper", "lower", "top", "bottom", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. When a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally arranged component at the same time.
[0130] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the article or device including the above elements.
[0131] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. 4H-SiC P-type heavy doping chemical potential controlled growth method, characterized in that, include: Providing SiC substrate; Preprocessing the SiC substrate; Introducing source gas to grow a P-type heavily doped 4H-SiC epitaxial layer on the surface of the pretreated SiC substrate; the source gas comprises: a C source gas, a Si source gas and a P-type doping source gas; During the growth process of the 4H-SiC epitaxial layer, the 4H-SiC epitaxial layer is grown starting from a C-rich atmosphere, and the SiC substrate is periodically in the C-rich atmosphere and the Si-rich atmosphere; the C-rich atmosphere is used to reduce the adsorption formation energy of P-type doping atoms and improve the adsorption strength of the 4H-SiC epitaxial layer on the surface of the SiC substrate; the Si-rich atmosphere is used to enhance the bonding ability between the adsorbed P-type doping atoms and the SiC crystal molecules and improve the growth rate of the 4H-SiC epitaxial layer.
2. The growth method according to claim 1, characterized in that The growth process of the 4H-SiC epitaxial layer includes a plurality of growth cycles, wherein the growth cycle includes a first stage in the C-rich atmosphere and a second stage in the Si-rich atmosphere; The sum of the durations of the first stage and the second stage is equal to the duration of the growth cycle, and the duration of the first stage is greater than the duration of the second stage.
3. The growth method according to claim 2, characterized in that: In the same growth cycle, the ratio of the duration of the first stage to the duration of the second stage is greater than 3 and less than 10.
4. The growth method according to claim 3, characterized in that: In the C-rich atmosphere, the P-type doping source gas is introduced at a fixed flow rate, and in the Si-rich atmosphere, the introduction of the P-type doping source gas is stopped.
5. The growth method according to claim 1, characterized in that: In the C-rich atmosphere, the chemical potential of C element Greater than -9.300000eV and less than -9.095729eV; In the Si-rich atmosphere, the chemical potential of Si element Greater than -5.742799eV and less than -5.419999eV.
6. The growth method according to claim 5, characterized in that: In the C-rich atmosphere, the ratio of C atoms to Si atoms is greater than 1 and not greater than 2; In the Si-rich atmosphere, the ratio of C atoms to Si atoms is not less than 0.5 and less than 1.
7. The growth method according to claim 1, characterized in that: During the growth of the 4H-SiC epitaxial layer, the flow rate of one of the C source gas and the Si source gas is constant, and the flow rate of the other can be switched between a first flow rate and a second flow rate to achieve switching between the C-rich atmosphere and the Si-rich atmosphere; The first flow rate is not equal to the second flow rate; and the switching duration between the first flow rate and the second flow rate is less than the duration of the first flow rate and the duration of the second flow rate.
8. The growth method according to claim 1, characterized in that: The SiC substrate has an offset angle of 4° to 8° along the <11-20> direction on the (0001) crystal plane of the SiC crystal.
9. The growth method according to claim 1, characterized in that: The method for pretreating the SiC substrate comprises: After heating and pressurizing the growth chamber, etching the surface of the SiC substrate to eliminate damage on the surface of the SiC substrate; During the pretreatment, the growth chamber has a first pressure and a first temperature; during the growth of the 4H-SiC epitaxial layer, the growth chamber has a second pressure and a second temperature; the first pressure is greater than the second pressure, and the first temperature is greater than the second temperature.
10. The growth method according to claim 1, characterized in that: During the growth of the 4H-SiC epitaxial layer, the temperature in the growth chamber ranges from 1500° C. to 1700° C.; and the growth pressure ranges from 80 mbar to 150 mbar.