阅读说明：本技术 非平衡条件下化学势调控生长单体的SiC台阶流快速生长方法 (SiC step flow rapid growth method for chemical potential regulation growth monomer under non-equilibrium condition ) 是由 康俊勇 林伟 陈浩南 陈心路 于 2021-08-13 设计创作，主要内容包括：本发明公开了非平衡条件下化学势调控生长单体的SiC台阶流快速生长方法。采用富C工艺(Si/H-(2)＝0.97‰,C/Si＝1.55)进行外延层高速生长,生长气氛中保持较高的C源相对化学势μ-(C)可以实现外延生长时优先吸附的生长单体为SiC分子,将生长台阶高度稳定在1/2c或1c,在实现高速外延生长的同时,得到较好的表面粗糙度和较低的离化掺杂浓度。(The invention discloses a SiC step flow rapid growth method for a chemical potential regulation growth monomer under a non-equilibrium condition. By C-rich process (Si/H) 2 0.97 thousandth, 1.55C/Si) is carried out, and a higher C source relative chemical potential mu is kept in the growth atmosphere C The growth monomer preferentially adsorbed during epitaxial growth is SiC molecules, the height of a growth step is stabilized at 1/2c or 1c, and good surface roughness and low ionization doping concentration are obtained while high-speed epitaxial growth is realized.)

1. The SiC step flow rapid growth method for regulating and controlling growth monomers by chemical potential under the non-equilibrium condition comprises the following steps:

1) preparing a silicon carbide substrate, wherein the silicon carbide substrate is a 4H-SiC substrate with steps;

2) heating a reaction cavity: heating the reaction cavity to a first temperature and keeping the temperature constant;

3) placing the reaction chamber at constant temperature: putting the 4H-SiC substrate in the step 1) into a bearing plate, and then putting the bearing plate and the substrate into a reaction chamber together, wherein the temperature of the reaction chamber is stabilized at a first temperature;

4) heating to a process temperature: the reaction cavity is heated to the process temperature, and simultaneously, the pressure of the reaction chamber is reduced to the set growth pressure;

5) in-situ etching: when the temperature of the cavity reaches the set process temperature, the substrate is maintained at the temperature for in-situ etching;

6) in situAfter etching, introducing source gas, and growing an epitaxial layer under the condition of rich C; wherein the epitaxial layer growth under the condition of rich C is controlled, i.e. the chemical potential mu of C is controlled_C；

7) Cooling and taking the slices; after the epitaxial growth is finished, the source gas is cut off and the temperature is reduced; and then taking the bearing disc and the epitaxial wafer out of the cavity.

2. The SiC step flow rapid growth method of chemical potential-modulated growth monomers under non-equilibrium conditions of claim 1, characterized in that: step 6) controlling the chemical potential mu of C_CIn which μ_CGreater than-9.300000 eV, μ_CLess than μ bCUlk, i.e., -9.095729 eV.

3. The SiC step flow rapid growth method of chemical potential-modulated growth monomers under non-equilibrium conditions of claim 2, characterized in that: c source and Si source flow Si/H₂0.97 per mill, 1.55 of C/Si, a high C chemical potential growth rate of 30 μm/h in a C-rich state and a step growth height of 1/2C.

4. The SiC step flow rapid growth method of chemical potential-modulated growth monomers under non-equilibrium conditions of claim 1, characterized in that: the first temperature is 850-950 ℃.

5. The SiC step flow rapid growth method of chemical potential-modulated growth monomers under non-equilibrium conditions of claim 1, characterized in that: in the step 6), the epitaxial growth temperature is 1500-1700 ℃, and the growth pressure is 80-150 mbar.

6. The SiC step flow rapid growth method of chemical potential-modulated growth monomers under non-equilibrium conditions of claim 1, characterized in that: the growth source gas comprises SiH₄、TCS、C₃H₈And C₂H₄At least one of (1).

7. The SiC step flow rapid growth method of chemical potential-modulated growth monomers under non-equilibrium conditions of claim 1, characterized in that: and the temperature rise in the step 4) is that the temperature is raised to 1400 ℃ at the speed of 20-30 ℃/min, and then the temperature is raised to the set process temperature at the speed of 10-15 ℃/min.

8. The SiC step flow rapid growth method of chemical potential control growth monomer under non-equilibrium condition of claim 1 or 7, characterized in that: the set process temperature is 1550-1670 ℃.

9. The SiC step flow rapid growth method of chemical potential-modulated growth monomers under non-equilibrium conditions of claim 1, characterized in that: and 5) in-situ etching parameters of pure hydrogen or pure hydrogen mixed with a small amount of growth source gas are 1-20 min.

10. The SiC step flow rapid growth method of chemical potential-modulated growth monomers under non-equilibrium conditions of claim 1, characterized in that: and 7) naturally cooling to the first temperature.

Technical Field

The invention relates to a SiC step flow rapid growth method for a chemical potential control growth monomer under a non-equilibrium condition.

Background

With the urgent need of high-temperature, high-power, high-voltage and radiation-resistant electronic devices in the fields of power transmission, power conversion, aerospace, military and nuclear power, wide-bandgap compound semiconductor materials represented by SiC, GaN, ZnO and the like are gradually attracting attention. The SiC material has the advantages of wide forbidden band width, high thermal conductivity, high breakdown field strength resistance, high saturated electron drift rate and the like.

Since the price of the SiC power device is still inferior to that of the same type of Si-based device, and the cost of the SiC power device needs to be reduced by increasing the wafer size, statistics of the YOLE company in france show that the cost of the 150mm 4H-SiC 1200V/20AMOSFET device is reduced by 45% compared with that of the 100mm 4H-SiC device of the same specification. Therefore, the large-size high-quality 4H-SiC thick film epitaxial wafer is obtained, the cost of the SiC device is reduced, the application of the SiC device in the high-voltage high-power field is expanded, and the development significance of the SiC industry is remarkable.

SiC materials differ in their periodic arrangement, and there are currently known approximately 250 polymorphic forms, whose structural properties present great difficulties in crystal growth. The most common crystal structures are 3C-SiC, 4H-SiC and 6H-SiC, wherein 4H-SiC is a silicon carbide semiconductor material which is most widely researched and applied at present, the forbidden band width is higher, the electron mobility is twice of that of 6H-SiC, and the silicon carbide semiconductor material is very suitable for preparing high-voltage high-power electronic devices. Currently, the common SiC Epitaxy methods mainly include Chemical Vapor Phase Epitaxy (CVPE), Liquid Phase Epitaxy (LPE), Sublimation (PVT), and Molecular Beam Epitaxy (MBE), each of which has a long time.

Compared with other epitaxial methods, Chemical Vapor Deposition (CVD) carries out chemical reaction by introducing source gas into a reaction chamber, and finally epitaxially grows a silicon carbide layer on the surface of a substrate. The doping concentration can be better controlled by adjusting the C/Si ratio and the nitrogen doping amount; by improving the source gas flow, reducing the pressure of the reaction chamber and the like, the growth speed can be effectively improved, and the growth efficiency is further improved; by adjusting the flow rate and the proportion of the carrier gas, the growth temperature and other parameters, the surface defect distribution and the epitaxial layer thickness uniformity can be effectively improved. Is very suitable for the mass production of silicon carbide epitaxy, and is the most popular 4H-SiC epitaxy method at present.

Because of the low energy of formation of stacking faults, silicon carbide crystals are prone to defect formation and even polymorphic inclusions during growth. The defects commonly seen in 4H-SiC crystal growth mainly include: polycrystalline Inclusions, Carbon Inclusions, Stacking Faults (SFs), Micropipes (MPs), Threading Screw Dislocations (TSD), Threading Edge Dislocations (TED), and Basal Plane Dislocations (BPD). Dislocation defects in the 4H-SiC substrate can gradually grow into the crystal along with the growth of the block crystal and cannot be completely removed through a technological method, so that the growth of a high-quality 4H-SiC homogeneous epitaxial layer is the basis for preparing a 4H-SiC power electronic device. Because the 4H-SiC material has stable physical and chemical properties, compared with the traditional silicon material, the diffusion doping is difficult to carry out, the 4H-SiC substrate material cannot be directly used for device preparation, and the material structure required by the device preparation must be completed through epitaxial growth.

For 4H-SiC epitaxial growth, due to the interaction of Van der Waals force between the C-Si double atomic layer layers, the difference of the formation energy of each stacking layer is small, and the stacking sequence can be changed due to slight disturbance in the growth process, so that the stacking fault defect occurs or other crystal forms are generated. Common 4H-SiC epitaxial defects include drops, triangular defects, carrot dislocations, micropipes, dislocations, and the like. The large-size 4H-SiC thick film low-doping epitaxial growth faces the following problems: (1) the 4H-SiC thick film epitaxy generally uses a high-speed growth process, so that step aggregation is easy to form, and basic theoretical research is lacked for the mechanism of step growth. (2) With the expansion of the size of the 4H-SiC wafer to 150mm, the growth atmosphere of different areas on the surface of the wafer is greatly different from that of the conventional 100mm epitaxy during the epitaxial growth, the radial source gas depletion difference is increased, the distribution uniformity of the thickness and the doping concentration in the wafer is difficult to guarantee, and a high-voltage high-power device not only needs a thicker epitaxy layer, but also needs extremely low doping concentration, so that the difficulty of the epitaxy process is high. Growing thicker epitaxial layers at lower rates results in more reduced productivity and significantly increased costs. It is also desirable to provide a high growth rate or short cycle time to improve yield in the production of epitaxial layers.

The 4H-SiC thick film epitaxy generally uses a high-speed growth process, so that step aggregation is easy to form, and an effective guidance scheme is lacked for a step growth mechanism. The technique of producing a large-sized 4H-SiC epitaxial layer with sufficient uniformity and low defect density in a short time is a current problem in the industry,

disclosure of Invention

In order to solve the technical problem, the invention provides a rapid SiC step flow growth method for regulating and controlling a growth monomer by chemical potential under a non-equilibrium condition.

The technical scheme adopted by the invention for solving the technical problem is as follows:

the SiC step flow rapid growth method for regulating and controlling growth monomers by chemical potential under the non-equilibrium condition comprises the following steps:

1) preparing a silicon carbide substrate, wherein the silicon carbide substrate is a 4H-SiC substrate with steps;

2) heating a reaction cavity: heating the reaction cavity to a first temperature and keeping the temperature constant;

3) placing the reaction chamber at constant temperature: putting the 4H-SiC substrate in the step 1) into a bearing plate, and then putting the bearing plate and the substrate into a reaction chamber together, wherein the temperature of the reaction chamber is stabilized at a first temperature;

4) heating to a process temperature: the reaction cavity is heated to the process temperature, and simultaneously, the pressure of the reaction chamber is reduced to the set growth pressure;

5) in-situ etching: when the temperature of the cavity reaches the set process temperature, the substrate is maintained at the temperature for in-situ etching;

6) after the in-situ etching is finished, introducing source gas, and growing an epitaxial layer under the condition of rich C; wherein the epitaxial layer is grown under C-rich conditions, i.e. underToChemical potential mu of C controlled between ranges_C(ii) a Wherein the content of the first and second substances,is C sheetThe chemical potential of the crystalline diamond is such that,is the enthalpy of formation of SiC;

7) cooling and taking the slices; after the epitaxial growth is finished, the source gas is cut off and the temperature is reduced; and then taking the bearing disc and the epitaxial wafer out of the cavity.

Preferably, the high C chemical potential μ_CIn which μ_CGreater than-9.300000 eV, μ_CIs less thanNamely-9.095729 eV.

Preferably, the C source and Si source flows Si/H₂0.97 per mill, 1.55 of C/Si, a high C chemical potential growth rate of 30 μm/h in a C-rich state and a step growth height of 1/2C.

Preferably, the first temperature is 850-950 ℃.

Preferably, in the step 6), the epitaxial growth temperature is 1500-1700 ℃, and the growth pressure is 80-150 mbar.

Preferably, the growth source gas comprises SiH₄、TCS、C₃H₈And C₂H₄At least one of (1).

Preferably, the temperature rise in the step 4) is that the temperature is raised to 1400 ℃ at the speed of 20-30 ℃/min, and then the temperature is raised to the set process temperature at the speed of 10-15 ℃/min.

Preferably, the set process temperature is 1550-1670 ℃.

Preferably, the in-situ etching parameter of the step 5) is pure hydrogen or pure hydrogen mixed with a small amount of growth source gas, and the time is 1-20 min.

Preferably, the temperature reduction of step 7) is natural temperature reduction to the first temperature.

Compared with the prior art, the method has the following beneficial effects:

1. silicon carbide capable of obtaining zero dislocation

2. The advantages brought by the growth of the epitaxial layer under the high-speed C-rich condition include

(1) The growth speed is high (30 mu m/h), the growth requirement of thick film epitaxy can be met, meanwhile, the adsorption monomer which preferentially participates in growth is SiC molecules, the growth step height is 1/2C, although the growth environment is in a C-rich state, the chemical potential of the C source is only required to be kept relatively low, the high step aggregation does not occur on the epitaxial surface, and the roughness is good.

(2) According to the competitive position principle, the relative chemical potential of the C source in the growth atmosphere is high, the difficulty of N atoms entering crystal lattices is high, and low-doping modulation doping can be carried out according to the requirements of devices;

(3) under the condition of C-rich growth, the transverse growth speed on the step table top is higher than the step growth speed, so that the BPD defects are converted into TED under the action of the mirror image force, and the conversion efficiency of the BPD defects can be increased.

Drawings

The invention is further illustrated by the following figures and examples.

FIG. 1 is a step surface model

FIG. 2 shows surface adsorption of Si_mC_nFormation energy of (2) is dependent on the chemical potential of Si

FIG. 3 shows that the fixed Si source flow is 0.26 ‰ Si/H2, and the influence of different C source flows on the surface morphology defects and the surface growth step height of 4H-SiC epitaxy

Detailed Description

A rapid SiC growth method for a chemical potential control growth monomer under a non-equilibrium condition comprises the following steps:

preparing a silicon carbide substrate, wherein the substrate is silicon carbide with steps:

and (5) raising the temperature. The reaction chamber was warmed from room temperature 20 ℃ to 900 ℃ using radio frequency heating and held at 900 ℃ at constant temperature.

And (5) placing the film at constant temperature. The 4H-SiC substrate intended for growth was placed into a carrier tray using a suction pen. The carrier plate and the substrate were then loaded into the reaction chamber by the robot, at which time the temperature of the reaction chamber was stabilized at 900 ℃.

Heating to the process temperature (1550-1670 ℃). The radio frequency generator heats the reaction cavity according to a set temperature rise speed. Meanwhile, the pressure in the reaction chamber is gradually reduced to the set growth pressure.

And (6) etching in situ. And when the temperature of the cavity reaches the set process temperature, keeping the temperature for carrying out in-situ etching on the substrate, wherein the etching time is 1-20 minutes.

4H-SiC growth is performed by chemical potential regulation, wherein the chemical potential regulation is distinguished based on the following principle:

ΔG_f＝E_tot-E_ref-Δn_Siμ_Si-Δn_Cμ_C (1.1)

wherein G is_fRepresenting the amount of change in the formation energy of each growth element adsorption model on the step surface relative to the clean step surface, E_totTotal energy of system representing step adsorption of atoms, molecules or clusters, E_refTotal energy, mu, representing clean step surface_SiAnd mu_CRespectively represent chemical potentials of Si and C elements,. DELTA.n_SiAnd Δ n_CRespectively, the amounts of change of Si atoms and C atoms in each growth structure with respect to the clean step surface. In equilibrium, the chemical potentials of a given species are equal in all phases in relation to each other, and assuming that the various step surfaces and bulk structures of 4H-SiC are balanced, the chemical potentials of the C and Si atoms will not be independent of each other, by expressionAre linked together, whereinShowing the chemical potential of the 4H-SiC crystal. The formation energy of each growth structure with respect to the clean step surface can be expressed as a formula related to only one atomic chemical potential, and then the formula (1.1) can be described as

In the actual growth of SiC materials, in order to avoid the difficulty of growing 4H-SiC by forming simple single crystal Si and diamond C metals, the chemical potentials of various atoms must satisfy

WhereinIs the enthalpy of formation of the SiC,chemical potential of C single crystal diamond, chemical potential μ of C_CIn the range of variation of(Si-rich state) to(C-rich state). The formation energy and C chemical potential μ of each adsorption structure are plotted according to the formula (1.1)_CWhen μ is shown in FIG. 2_CThe growth environment gradually tends to a C-rich state when the temperature is more than-9.300000 eV, the stability of adsorbing SiC molecules at the step boundary of 1/4C is strongest, and Si atoms are arranged next to the step boundary, so that C-Si adsorption does not occur at the moment₂The case of clusters. In this state, the formation of different step surfaces adsorbing SiC molecules can be related as follows: the formation energy of the four adsorption structures is similar in pairs, the formation energy of S1+ SiC and S3+ SiC is lower than that of S2+ SiC and S4+ SiC, the growth speed of the steps S1 and S3 is higher, the steps S2 and S4 can be easily caught up, a double-step growth mode is formed, and the height of the grown steps is 1/2c (half the height of a 4H-SiC unit cell).

According to the principle, the ratio of C to Si in the growth atmosphere is adjusted, and 4H-SiC low-speed growth is carried out in a C-rich state. After the in-situ etching is finished, source gas is introduced, and the growth is carried out under the condition of low speed and rich C (Si source flow is selected as: Si/H)₂0.97%, C/Si 1.55, growth rate about 30 μm/h). Introducing silicon source TCS and carbon source C according to a set flow₂H₄And doping gas source N₂And maintaining the set growth time to finish the 4H-SiC epitaxial growth with the specific thickness.

And finally, cooling and taking the tablets. And after the epitaxial growth is finished, the source gas is turned off, and the radio frequency source is turned off to directly cool. When the temperature reaches 900 ℃, the radio frequency source is turned on again to keep the temperature constant at 900 ℃. And simultaneously, the bearing disc and the epitaxial wafer can be taken out of the cavity by the mechanical arm.

According to the invention, the step of the SiC substrate is preferably arranged alongAnd removing the uppermost C-Si double atomic layer on one side in the crystal plane direction.

Preferably, according to the invention, the growth source comprises SiH₄、TCS、C₃H₈And C₂H₄And the like.

According to the invention, the preferable growth temperature is 1500-1700 ℃, and the growth pressure is 80-150 mbar.

According to the invention, in step (2), the C source and the Si source flow Si/H₂0.97 per mill, 1.55C/Si, a growth rate of about 30 μm/h, and a step growth height of 1/2C.

Establishing a step surface model based on a 5X 3 4H-SiC unit cell, cutting along the vertical direction of a (0001) crystal plane at a selected diatomic layer interface to obtain 4H-SiC of a flat Si polar surface, and cutting along the back edgeAnd (4) removing the C-Si diatom layer on the uppermost layer on the right side along the crystal plane direction to finally obtain the 4H-SiC step model. The C-Si diatomic layers in the 4H-SiC crystal are stacked in … ABCB … sequence, 4 kinds of step structures can exist when the step height is 1/4C, and the structure is composed of inner and outer stacks of ABCB, BCBA and CBAB respectively, which are marked as S1, S2, S3 and S4 respectively, as shown in the attached figure 1, each of which is composed of 5 x 1 atom thin layers and vacuum layers, wherein 4 pairs of C-Si diatomic layers are contained, and the C-Si diatomic layers are reserved in the C-axis directionThe vacuum layer is used for eliminating the mutual influence of surface atoms of the upper layer and the lower layer, the directions of the a axis and the b axis are periodically expanded, the dangling bond of the C atom at the bottom layer of each step structure is passivated by H atoms, and the whole step structureThe atoms in the structure may each be relaxed optimally along the c-axis. The cutoff energy of the plane wave at the time of calculation was 400eV, and the grid points were set to 8 × 8 × 8.

According to simulation calculation, the trend of the formation energy of the growth adsorption structure along with the change of relative chemical potential is drawn as shown in figure 2, when 4H-SiC epitaxial growth is carried out in a C-rich state, the adsorption monomer which preferentially participates in growth is Si-C molecules, the height of a growth step is 1/2C, and a double-step growth mode appears. From the simulation calculation results of the double-step adsorption of different growth monomers, Si atoms, Si-C molecules (preferentially adsorbing C atoms) and C-Si can be known₂Three monomers of the cluster can be stably adsorbed at the double-step boundary. With the increasing of the relative chemical potential of C, the double steps adsorb Si atoms and Si₂The formation energy of the C cluster is gradually reduced, the stability is continuously enhanced, and no matter the growth environment is in a Si-rich or C-rich state, C-Si is adsorbed at the step boundary₂The stability of the cluster is strongest, and two different double steps S1 'and S3' adsorb C-Si₂Since the cluster formation energy is substantially the same, the height of the growth step is maintained at 1/2c, and a good epitaxial surface roughness can be obtained.

The equipment for 4H-SiC homoepitaxial growth is a rotary single-chip hot-wall reaction furnace, the system adopts radio frequency heating, the temperature gradient of the surface of the 150mm 4H-SiC substrate can be effectively controlled below 10K/cm, the over-cooling degree of the surface is avoided, and the defect of thermal stress introduction is reduced. The rotating base can effectively improve the radial distribution of source gas on the surface of the wafer in the growth process, and is beneficial to the adjustment of the thickness and the non-uniformity of the doping concentration. A high-speed SiC growth method for regulating growth monomers by chemical potential under non-equilibrium conditions comprises the following steps:

the substrate used for epitaxial growth is a 150mm 4H-SiC substrate which is obliquely cut by deviating 4 degrees from the same crystal ingot in the same manufacturer, and the influence of the substrate processing technology or the crystalline quality on the epitaxial result is avoided. The equipment automatically puts and takes the wafer through the manipulator at high temperature, and a 150mm 4H-SiC epitaxial wafer grows in a single furnace, and can be compatible for 100mm epitaxial growth. The typical growth source is SiHCl₃(TCS) and C₂H₄The N-type doping source is N₂The P-type doping source is TMAl, hydrogen as carrier gas. Spare parts in the cavity are made of graphite materials, and can be quickly heated and keep the temperature of the cavity. The graphite base has an air floatation rotation function, and can enable the substrate to carry out epitaxial growth in a rotation state. A typical growth temperature for a 4H-SiC substrate is 1650 ℃.

Preparing a 4H-SiC substrate with steps: and (3) heating the reaction cavity to 900 ℃ from room temperature by using radio frequency heating, and keeping the reaction cavity at constant temperature after the reaction cavity reaches the target temperature. The 4H-SiC substrate intended for growth was then placed on a carrier plate using a suction pen, and the carrier plate and the substrate were loaded into the reaction chamber together by a robot arm, at which time the temperature of the reaction chamber was stabilized at 900 ℃. And then the radio frequency generator heats the reaction cavity according to the set temperature rise speed. Meanwhile, the pressure in the reaction chamber is gradually reduced to the set growth pressure. When the temperature in the cavity reaches 1400 ℃, the temperature rise speed is reduced, and the temperature is slowly raised to the set process temperature (1550-1670 ℃). And then etching in situ. And when the temperature of the cavity reaches the set process temperature, keeping the temperature for carrying out in-situ etching on the substrate, wherein the etching time is 1-20 minutes. In the etching process, a small amount of silicon source or carbon source is needed to be introduced to control the desorption speed of Si atoms and C atoms on the surface of the substrate, and finally the 4H-SiC substrate with steps is obtained.

In order to obtain higher epitaxial growth speed, the Si source flow is set to Si/H₂The C source flow is set to be C/H respectively under 0.97 ‰₂1.21 per mill, 1.50 per mill and 1.70 per mill (C/Si ratio: 1.25, 1.55 and 1.75 respectively), and the epitaxial growth speed is more than or equal to 25 μm/h under the three conditions. Three 150mm 4H-SiC substrates used for sample growth are the same as those used in the low-speed growth experiment and are all from the same crystal ingot of the same manufacturer. The thicknesses of the 4H-SiC high-speed epitaxial samples D, E and F are both about 12 μm, and surface morphology defect detection and roughness detection are respectively carried out, wherein when AFM is used for surface roughness detection, the scanning size is also 1 μm multiplied by 1 μm, and the obtained result is shown in figure 3. The C/Si ratio of sample D was 1.25, the number of triangles and carrot dislocations on the epitaxial surface was large, and the surface defect density reached 1.33cm^-2The defects were uniformly distributed over the entire wafer, the surface roughness RMS was 0.31nm, and the height of the growth step was 1/2C, indicating that when the C source flow was set to C/H₂When the carbon source is 1.21 per mill, the relative chemical potential of the carbon source is high, the growth environment is in a carbon-rich state during epitaxial growth, and the step growth mainly adsorbs SiC molecules. Sample E had a C/Si ratio of 1.55, resulting in a low number of epitaxial surface defects with a defect density of 0.59cm^-2. The surface roughness RMS is 0.41nm, the flow of the C source can enable the growth environment to be in a C-rich state, the epitaxial growth mainly adsorbs SiC molecules, the height of a growth step is 1/2C, but the C source has high flow and relatively large chemical potential due to the high flow of the C source, so that the step aggregation phenomenon (the aggregation height is about 1nm, and the width of an aggregated mesa is about 200-300 nm) occurs on the growth surface. The C/Si ratio of the sample F is 1.75, the number of surface defects is obviously increased, and the defect density reaches 1.22cm^-2The surface roughness RMS reaches 0.68nm, meanwhile, the surface has obvious step aggregation phenomenon, the step aggregation height reaches 3-4 nm, and the width of the formed table board is about 150-200 nm.

The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims and their equivalents.