CN113564710A

CN113564710A - Control method for silicon carbide epitaxial growth

Info

Publication number: CN113564710A
Application number: CN202110813657.XA
Authority: CN
Inventors: 刘杰; 钱卫宁; 冯淦; 赵建辉
Original assignee: Epiworld International Co ltd
Current assignee: Hantiantiancheng Electronic Technology Xiamen Co ltd
Priority date: 2021-07-19
Filing date: 2021-07-19
Publication date: 2021-10-29
Anticipated expiration: 2041-07-19
Also published as: CN113564710B

Abstract

The invention relates to a control method for silicon carbide epitaxial growth, which comprises the steps of placing a substrate in a closed chamber, introducing a carbon source and a silicon source, growing an epitaxial layer on the surface of the substrate, defining the initial flow value of the carbon source as asccm and the end value as b sccm; the initial flow value of the silicon source is a ' sccm, the end value is b ' sccm, and when the flow of the carbon source is b sccm and the flow of the silicon source is b ' sccm, the epitaxial layer starts to grow; changing the flow rate of the carbon source from a sccm to b sccm in the T s internal segment k, and changing the flow rate of the silicon source from a ' sccm to b ' sccm in the T s internal segment k ', wherein the flow rate changes of the carbon source and the silicon source are controlled by a sectional control method.

Description

Control method for silicon carbide epitaxial growth

Technical Field

The invention relates to the technical field of silicon carbide, in particular to a control method for epitaxial growth of silicon carbide.

Background

The silicon carbide epitaxial material has wide application in monocrystalline silicon, polycrystalline silicon, intelligent equipment, aerospace, electric vehicles, rail transit, new energy development, industrial motors, household appliances and other fields, and is an object of national industry oriented preferential development.

At present, silicon carbide epitaxial layers are switched among different air source flows by using a linear gradual change method, the air source flow changes at a constant speed in a specified time, the change among the air source flows is completed by using a linear change mode commonly used in the industry at present, the air source flow change of epitaxial furnace equipment on the market at present is defaulted to use linear change, the equipment is only in a linear change mode, and meanwhile, people in the industry do not pay attention to and try to change the influence of the air source flow change mode of a transition layer on the epitaxial quality.

Patent application CN102646578A discloses a method for improving the doping concentration uniformity among silicon carbide multilayer structure epitaxial material batches, which is based on the chemical vapor deposition growth technology, after the (0001) silicon surface silicon carbide substrate biased to <11-20> direction by 8 degrees is pretreated, pure silane and pure propane are used as growth sources, hydrogen is used as carrier gas and diluent gas, and nitrogen is selected as dopant to realize n-type doping. The method sets different growth rates and different carbon-silicon ratios of the air inlet end in the thickness and the doping concentration of each epitaxial layer, adopts a low-speed epitaxy method combined with a method of reducing the carbon-silicon ratio of the air inlet end to grow thin-layer epitaxy with high doping concentration, adopts a high-speed epitaxy method combined with a method of improving the carbon-silicon ratio of the air inlet end to grow high-resistance thick-layer epitaxy, and adopts a high-speed epitaxy method to grow a channel layer with required concentration and thickness so as to reduce the background memory effect.

Disclosure of Invention

The invention aims to overcome the defects in the existing silicon carbide epitaxial growth technology and provide a control method for silicon carbide epitaxial growth.

The most ideal technology is that no transition layer exists, the source gas flow of the buffer layer is directly sheared to the epitaxial source gas flow, the prior art cannot meet the requirement, the source gas flow of the traditional silicon carbide epitaxial growth buffer layer is changed to the epitaxial layer source gas flow in a linear gradual change mode, a transition layer is inevitably formed on the surface of the buffer layer correspondingly, in order to make the thickness of the transition layer as thin as possible, the change time can only be reduced, so that the source gas flow change speed is too fast, because the initial flow of the transition layer is small, the initial flow change speed can be large in proportion of the initial flow change quantity to the initial flow, the initial flow is unstable, and the epitaxial surface quality is poor. Obviously, in the current linear ramp mode, the improvement of the epitaxial surface quality cannot be realized while the transition time is short. Whereas a long transition time means that the transition layer grows too thick.

Therefore, the inventor pays attention to the defects of the source air flow change mode of the current transition layer, breaks through the conventional mode, and considers completely different flow change modes: the flow change speed of the air source is controlled artificially, the flow change speed is lower at the initial stage of the transition layer, the flow change speed is continuously increased along with the time, the effect that the front part is slow and the back part is fast is achieved, compared with a linear change mode, the method can grow thinner transition layer thickness while the same flow is changed in the same time, meanwhile, the proportion that the initial flow change amount of the transition layer is smaller is guaranteed, and the epitaxial stable growth is guaranteed.

At present, a linear gradual change mode is generally used in the industry to complete the change between the air source flows, the air source flow change mode of the epitaxial furnace equipment in the market defaults to use linear change, and the equipment is only in a linear change mode, and meanwhile, people in the industry do not pay attention to and try to change the influence of the air source flow change mode of a transition layer on the epitaxial quality, so that the existing method cannot realize staged control, the inventor proposes a mode of artificially controlling a transition point and a transition value through mathematical transformation, and tests prove that the high improvement of the product quality can be obtained, and the method comprises the following steps: the surface roughness Rq of the product silicon carbide epitaxial wafer is 0.144nm < 0.15nm, and the epitaxial surface critical defect density (including triangle, carrot and falling defect) is 0.292/cm²Less than 0.3 pieces/cm². Compared with the conventional linear gradual change, the method can be used for realizing the equivalent transitionAnd a transition layer with thinner thickness is grown in time, and the thickness precision of the outer extension layer and the product quality are ensured to be improved.

The specific scheme is as follows:

a control method for silicon carbide epitaxial growth comprises the steps of placing a substrate in a closed chamber, introducing a carbon source and a silicon source, growing a buffer layer and an epitaxial layer on the surface of the substrate, and defining an initial flow value of the carbon source, namely the flow value of the carbon source is asccm when the buffer layer grows; the end value of the flow of the carbon source, namely the flow value of the carbon source during epitaxial layer growth is bsccm; the flow initial value of the silicon source, namely the flow value of the silicon source is a 'sccm when the buffer layer grows, and the flow finishing value of the silicon source, namely the flow value of the silicon source is b' sccm when the epitaxial layer grows; when the flow rate of the carbon source is bsccm and the flow rate of the silicon source is b' sccm, starting the growth of the epitaxial layer;

changing the flow of the carbon source from asccm to bsccm in a section k in Ts, and changing the flow of the silicon source from a ' sccm to b ' sccm in a section k ' in Ts, correspondingly forming a transition layer on the surface of the buffer layer, wherein the transition layer is located between the buffer layer and the epitaxial layer, a, b, a ', b ', T, k and k ' are respectively positive numbers, b > a, b ' > a ', k is greater than or equal to 2, and k ' is greater than or equal to 2, the flow change of the carbon source and the silicon source during the growth of the transition layer is controlled by a sectional control method, specifically, taking the carbon source as an example, the corresponding relationship between the time and the flow of each stage in the sectional control method is as follows:

wherein the flow rate variation process in the sectional control method comprises:

stage 1: the flow rate is graded from a to D1 within deltat 1s,

stage 2: the flow rate is gradually changed from D1 to D2 in delta T2s,

stage 3: the flow rate is gradually changed from D2 to D3 in the delta T3s,

… …, and so on, section n: the flow rate is at delta T_nWithin s by D_n-1Gradual change to D_n；

Until the k-th segment: the flow rate is at delta T_kWithin s by D_k-1Gradual change to D_k；

And the flow change of the silicon source is calculated by adopting a formula in the sectional control method according to the values of a ', b', T and k ', the calculation mode is the same as that of the carbon source, and only a' replaces a and b 'in the table for b and k' in the table.

Further, the initial value of the carbon source is: a is more than or equal to 16 and less than or equal to 162.5, and the initial value of the silicon source is as follows: a' is more than or equal to 40 and less than or equal to 250, and the carbon-silicon ratio during the growth of the buffer layer is ensured to be between 0.8 and 1.3.

Further, the end value of the carbon source: b is more than or equal to 125 and less than or equal to 480, and the ending value of the silicon source is as follows: b' is more than or equal to 250 and less than or equal to 600, and the carbon-silicon ratio during the growth of the epitaxial layer is ensured to be between 1.0 and 1.6.

Further, during the sectional control method, the carbon-silicon ratio is between 0.8 and 1.6.

Furthermore, the time T is between 10 and 600s, and the number k of the sections is between 2 and 200.

Furthermore, the time T is between 40 and 200s, and the number k of the sections is between 5 and 20.

Further, the carbon source is ethylene or propane, and the silicon source is trichlorosilane or silane.

Furthermore, the flow rate of the carbon source and the flow rate of the silicon source are gradually changed by the sectional control method, so that the flow rate change speed of the carbon source and the flow rate change speed of the silicon source are gradually increased, and the change speed of the carbon-silicon ratio is gradually increased, so as to reduce the growth thickness of the transition layer in the flow rate change process.

The invention also provides a control method for epitaxial growth of the silicon carbide and a silicon carbide epitaxial wafer prepared by the control method, wherein the surface roughness Rq of the silicon carbide epitaxial wafer is less than 0.15 nm.

Furthermore, the density of the surface fatal defects of the silicon carbide epitaxial wafer is less than 0.3/cm²The surface critical defects include triangles, carrots and drop defects.

Has the advantages that:

the invention provides a control method for epitaxial growth of silicon carbide, which uses a sectional control method to carry out change control on the gas source flow of a carbon source and a silicon source before the epitaxial layer grows, and divides the flow change time into k and k' stages by combining a mathematical algorithm so as to realize the increase of the silicon source flow change speed (namely acceleration increase) and the increase of the carbon-silicon ratio change speed (namely acceleration increase) in the whole gas source change process, specifically, the silicon source flow is slowly increased in the early stage, the silicon source flow is increased at a higher speed in the later stage, the corresponding change of the carbon-silicon ratio is slowly increased in the early stage, and is increased at a higher speed in the later stage.

By adopting the control method, the variation can be correspondingly smaller when the source gas flow is smaller in the initial stage, so that the proportion of the initial flow variation of the transition layer to the initial flow is facilitated, and the stable growth of epitaxy is facilitated. Specifically, the source gas flow of the buffer layer is small, and the early-stage flow change of the transition layer should be small, so that the ratio of the source gas variation to the original flow is small, and as the flow increases, when the epitaxial layer is approached, the flow is relatively large, and at this time, the flow variation can be appropriately increased. For example, when the flow rate of the buffer layer is 60sccm, the linear variation is increased to 240sccm within 60s, and the variation rate is 3sccm/s, the initial variation ratio is 3/60 to 5%, and the initial variation ratio can be made less than 5% by using the stepwise variation.

By adopting the control method, compared with the conventional linear slow change, the sectional change can change the same flow rate in the same time, and simultaneously grow a transition layer with thinner thickness.

Drawings

In order to illustrate the technical solution of the present invention more clearly, the drawings will be briefly described below, and it is apparent that the drawings in the following description relate only to some embodiments of the present invention and are not intended to limit the present invention.

FIG. 1 is a sectional variation phase source gas flow chart provided by one embodiment 1 of the present invention;

FIG. 2 is a graph of the variation of C/Si with time in a stepwise variation phase provided by an embodiment 1 of the present invention;

FIG. 3 is a graph of the total process source gas flow rate control provided by one embodiment 1 of the present invention;

FIG. 4 is a graph of the variation of the control global C/Si over time provided by one embodiment 1 of the present invention;

FIG. 5 is a plot of source gas flow for a linear ramp process as provided in comparative example 1, in accordance with the present invention;

FIG. 6 is a graph of the linear ramp process C/Si provided by comparative example 1 of the present invention over time;

FIG. 7 is a graph of the total process source gas flow rate control provided in comparative example 1 of the present invention;

FIG. 8 is a graph of the change in C/Si over time over the course of control provided by comparative example 1 of the present invention.

FIG. 9 is a graph of source gas flow provided by comparative example 2 of the present invention;

FIG. 10 is a graph showing the change of C/Si with time according to comparative example 2 of the present invention;

fig. 11 is a view of a silicon carbide epitaxial surface roughness measurement provided in accordance with an embodiment 1 of the present invention;

fig. 12 is a view for detecting defects on an epitaxial surface of silicon carbide provided in accordance with embodiment 1 of the present invention;

FIG. 13 is a view of a silicon carbide epitaxial surface roughness measurement provided by comparative example 1 of the present invention;

fig. 14 is a view for detecting defects on the epitaxial surface of silicon carbide provided in comparative example 1 of the present invention.

Detailed Description

Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available. In the following examples, "%" means weight percent, unless otherwise specified.

The main improvement of the invention is the flow change mode of the carbon source and the silicon source, namely the flow change is carried out between the growth of the buffer layer and the growth of the epitaxial layer, and the sectional control method is adopted to generate an extremely thin transition layer corresponding to the stage, and the thickness of the transition layer can be ignored compared with the thickness of the epitaxial layer. Other techniques such as substrate cleaning, etching, venting, doping, epitaxial wafer growth equipment, etc. may be used as is known in the art.

The sectional control method adopts the formula in the table 1 to calculate, the flow change calculation formulas of the carbon source and the silicon source are the same, and only the respective substituted numerical values are different, namely the carbon source is calculated according to the values of a, b, T and k, and the silicon source is calculated according to the values of a ', b ', T and k '. It should be noted that table 1 lists the calculation formula by taking the carbon source as an example, and the silicon source calculation formula is the same as the carbon source except that a ' replaces a, b ' in the table and b, k ' replaces k in the table.

Preferably, the initial value of the carbon source is: a is more than or equal to 16 and less than or equal to 162.5, and the initial value of the silicon source is as follows: a' is more than or equal to 40 and less than or equal to 250, and the carbon-silicon ratio during the growth of the buffer layer is ensured to be between 0.8 and 1.3.

Preferably, the end value of the carbon source is: b is more than or equal to 125 and less than or equal to 480, and the ending value of the silicon source is as follows: b' is more than or equal to 250 and less than or equal to 600, and the carbon-silicon ratio during the growth of the epitaxial layer is ensured to be between 1.0 and 1.6.

Through the two conditions, the growth quality of the epitaxial layer can be ensured, preferably, during the sectional control method, the carbon-silicon ratio is 0.8-1.6, so that a better carbon-silicon ratio is always maintained in a growth space, and growth defects are reduced. The carbon to silicon ratio is more preferably 1.0 to 1.3.

In the calculation formula, the T and k involved are not limited in principle. And the larger the k value is, the flow curve is close to smooth, and the better the product quality is under the ideal condition, but the more k is, the lower the significance is in consideration of the change limit of the flow meter in unit time (the sensitivity of the flow meter), the workload of manually writing a calculation program and other factors. In the invention, the time T is preferably between 10 and 600s, the number k of the stages is between 2 and 200, more preferably the time T is between 40 and 200s, and the number k of the stages is between 5 and 20.

As will be apparent from the following embodiments, it is clear that, according to a calculation formula, the carbon source and the silicon source are switched in a staged control manner, and the change speed of the silicon source flow rate increases (i.e., the acceleration increases), the change speed of the carbon-silicon ratio increases (i.e., the acceleration increases), specifically, the early-stage silicon source flow rate slowly increases, the later-stage silicon source flow rate increases at a greater speed, the corresponding change of the carbon-silicon ratio slowly increases at the early stage, and the later-stage silicon ratio increases at a faster speed. Therefore, the specific values in the embodiments do not limit the present invention, and the change rules of the carbon source and the silicon source can be predicted according to the calculation formula, so as to obtain the advantageous effects of the present invention.

Example 1

A control method for silicon carbide epitaxial growth, a silicon source adopts TCS (trichlorosilane), a carbon source adopts C2H4 (ethylene), and the main steps are as follows:

the first step is as follows: selecting a silicon surface silicon carbide substrate deflected to the direction of <11-20> by 4 degrees, carrying out standard cleaning, and then placing the substrate in a reaction chamber;

the second step is that: vacuumizing the reaction chamber, introducing hydrogen, keeping the hydrogen flow at 150-200L/min, keeping the pressure of the reaction chamber at 80-100 mbar, and heating the reaction chamber from room temperature to 1300 ℃ at a fixed heating rate of 34 ℃/min in a radio frequency heating mode; then reducing the heating rate to 16 ℃/min, heating to 1625-1675 ℃, and etching at constant temperature for 5-20 minutes;

the third step: introducing mixed gas of a silicon source and a carbon source into the reaction chamber, setting the flow of the silicon source as a' sccm (low-speed growth), setting the flow of the carbon source as asccm, using high-purity nitrogen (N2) as a doping source, and growing an N-type buffer layer with the thickness of 0.3-2 um and the doping concentration of more than 1E18 cm-3;

the fourth step: the silicon source and carbon source flows were increased to b' sccm and bscm, respectively, using a stepwise variation. And continuously introducing high-purity nitrogen (N2) to grow to a target thickness, wherein the doping concentration is the N-type epitaxial layer of the target doping concentration.

The fifth step: and closing the growth source and the doping source, and cooling the temperature of the reaction chamber to room temperature in a hydrogen atmosphere. And introducing argon to replace hydrogen in the reaction chamber, vacuumizing the reaction chamber to 0mbar, maintaining for 5 minutes, introducing argon into the reaction chamber to atmospheric pressure, opening the reaction chamber, and removing the epitaxial wafer.

In the above steps, the third step is to prepare for epitaxial growth, and the parameters are designed as follows:

buffer layer parameters (initial values): the silicon source a' was 60sccm and the carbon source a was 31.5sccm, in which case the carbon-to-silicon ratio was 1.05 sccm

Epitaxial layer parameters (end value): the silicon source b' is 240sccm, the carbon source b is 138sccm, and the carbon-silicon ratio is 1.15

Total time of change: t100 s

Both TCS and C2H4 use segmented control: control is performed in 10 steps, i.e., k ═ 10, and the calculation is performed according to table 1 below, and pieces of control data are obtained, as shown in table 2.

In table 1, the carbon source is used as an example to show the calculation formula, and the silicon source is calculated by using a ' instead of a and b ' in table 1 instead of b and k ' in table 1, which is the same as the calculation formula of the carbon source.

TABLE 1 sectional control calculation formula table

TABLE 2 segmented control parameter table

For illustrative purposes, the data in table 2 are plotted, see fig. 1 and 2, with the slope of the tangent to the curve increasing as can be seen from fig. 1, indicating that: the flow rates, i.e., the acceleration rates, of the carbon source and the silicon source increase. Since the silicon carbide growth rate is mainly determined by the silicon source flow rate, the area S1 of the pattern under the curve of the silicon source flow rate in fig. 1 is calculated, and S1 is 9600sccm · S.

Fig. 2 shows the change of the carbon-silicon ratio during the flow rate change, and as can be seen from fig. 2, the slope of the tangent line of the curve increases gradually, which illustrates that: the rate of change of the carbon-silicon ratio, i.e., the acceleration, tends to increase.

In view of the whole control process, the variation curve of the source gas flow is shown in fig. 3, the source gas is kept unchanged at the buffer layer stage and the epitaxial layer stage, the source gas flow is in an increasing trend at the transition layer stage, and the increasing speed is continuously increased along with the time.

Fig. 4 shows the variation of the carbon-silicon ratio in the whole control process, and it can be seen from fig. 4 that the carbon-silicon ratio is kept constant in the buffer layer and epitaxial layer stages and gradually increases in the transition layer stage.

Fig. 11 is a surface roughness measurement of an epitaxial wafer grown by the step control technique, Rq 0.144 nm.

FIG. 12 is a surface defect detection map of an epitaxial wafer grown by a step control technique, with a circular area corresponding to a material area of 160.7cm²The dots are the positions of the fatal defects, the total number of 47 positions is 0.292/cm²。

Comparative example 1

Referring to example 1, the difference is that in the third step and the fourth step, the conventional linear graded technique is used to control the epitaxial growth of silicon carbide, the silicon source is TCS (trichlorosilane), the carbon source is C2H4 (ethylene), and the parameters are designed as follows:

Total time of change: t100 s, TCS and C2H4 were all conventionally linear ramped with specific control data as shown in table 3.

TABLE 3 Linear ramp control parameter Table

Fig. 5 shows the change of the source gas flow rate curve with time in the linear ramp process. As can be seen from fig. 5, the rate of change of the source gas flow rate was kept constant, and since the silicon carbide growth rate was mainly dependent on the silicon source flow rate, the area of the graph S2 under the silicon source flow rate curve in fig. 5 was calculated, S2 being 15000sccm · S. Compared with the calculation results of FIG. 1, S2 > S1. The sectional change transition layer reduces relative to the linear change transition layer: (15000-.

Fig. 6 shows the change of the carbon-silicon ratio during the flow rate change, and as can be seen from fig. 6, the slope of the tangent line of the curve gradually decreases, which illustrates that: the rate of change of the carbon-silicon ratio, i.e., the acceleration, tends to decrease.

In the whole control process, the change curve of the source gas flow is shown in figure 7, the source gas is kept unchanged in the buffer layer stage and the epitaxial layer stage, the source gas flow is in an increasing trend in the transition layer stage, and the increasing speed is kept unchanged.

Fig. 8 shows the variation of the carbon-silicon ratio in the whole control process, and it can be seen from fig. 8 that the carbon-silicon ratio is kept constant in the buffer layer and epitaxial layer stages, and the variation speed of the carbon-silicon ratio gradually becomes slower in the transition layer stage.

Fig. 11 is a graph showing the surface roughness of an epitaxial wafer grown by the linear graded control technique, wherein Rq is 0.391 nm.

FIG. 12 is a surface defect detection diagram of an epitaxial wafer grown by linear graded control technique, wherein the circular area corresponds to a material area of 160.7cm²The dots are the positions of the fatal defects, the total number of the fatal defects is 83, and the density of the fatal defects is 0.516/cm²。

Comparative example 2

TCS (trichlorosilane) is adopted as a silicon source, C2H4 (ethylene) is adopted as a carbon source, and the parameters are designed as follows:

Total time of change: t100 s, TCS uses segmented control: control is performed in 10 steps, i.e., k is 10, and calculation is performed according to table 1 to obtain segmented control data, see table 4. The C2H4 was subjected to conventional linear ramp, and the specific control data are shown in Table 4.

TABLE 4 flow control parameter table for source gas

Fig. 9 shows the change of the source gas flow rate over time. As can be seen from fig. 9, the slope of the C2H4 flow curve remains constant and the slope of the tangent to the TCS curve increases gradually. This indicates that: the speed of the C2H4 flow change is kept constant, and the speed of the TCS flow change, namely the acceleration, is in an increasing trend

Fig. 10 shows the change of the carbon-silicon ratio during the flow rate change, and it can be seen from fig. 10 that the carbon-silicon ratio increases and then decreases with time, and the carbon-silicon ratio is greater than 1.6 during the process, which is beyond the reasonable range. Too high a carbon to silicon ratio results in very poor epitaxial surface quality and is therefore unsuitable for epitaxial growth of silicon carbide.

Example 2

A control method for silicon carbide epitaxial growth, a silicon source adopts silane, a carbon source adopts propane, and the method comprises the following steps:

In the above step, in preparation for epitaxial growth, parameters are designed as follows:

buffer layer parameters (initial values): silicon source a' 100sccm and carbon source a 35sccm, with a carbon to silicon ratio of 1.05

Epitaxial layer parameters (end value): silicon source b' 300sccm and carbon source b 115sccm, wherein the carbon-to-silicon ratio is 1.15

Total time of change: t100 s

Both silane and propane were controlled stepwise: control was performed in 10 steps, i.e., k ═ 10, and the calculation was performed according to table 1 below, and pieces of control data were obtained, as shown in table 5.

TABLE 5 segmented control parameter table

The obtained epitaxial wafer was examined to find that the surface roughness Rq was 0.15 nm. The density of the surface fatal defects is less than 0.3/cm²The surface critical defects include triangles, carrots and drop defects.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. A control method for silicon carbide epitaxial growth is characterized in that: placing a substrate in a closed chamber, introducing a carbon source and a silicon source, growing a buffer layer and an epitaxial layer on the surface of the substrate, and defining an initial flow value of the carbon source, namely the flow value of the carbon source is a sccm during the growth of the buffer layer; the end value of the flow of the carbon source, namely the flow value of the carbon source during epitaxial layer growth is b sccm; the flow initial value of the silicon source, namely the flow value of the silicon source is a 'sccm when the buffer layer grows, and the flow finishing value of the silicon source, namely the flow value of the silicon source is b' sccm when the epitaxial layer grows; when the flow rate of the carbon source is b sccm and the flow rate of the silicon source is b' sccm, starting the growth of the epitaxial layer;

changing the flow rate of the carbon source from a sccm to b sccm in T s by k segments, and simultaneously changing the flow rate of the silicon source from a 'sccm to b' sccm in T s by k segments, correspondingly forming a transition layer on the surface of the buffer layer, where the transition layer is located between the buffer layer and the epitaxial layer, where a, b, a ', b', T, k, and k 'are each independently positive numbers, and b > a, b' > a ', k is greater than or equal to 2, and k' is greater than or equal to 2, and when the transition layer grows, the flow rate changes of the carbon source and the silicon source are controlled by a sectional control method, specifically, taking the carbon source as an example, the corresponding relationship between the time and the flow rate of each stage in the sectional control method is as follows:

stage 1: the flow rate is gradually changed from a to D1 in the delta T1s,

stage 2: the flow rate is gradually changed from D1 to D2 in delta T2s,

stage 3: the flow rate is gradually changed from D2 to D3 in delta T3s,

2. A method of controlling epitaxial growth of silicon carbide according to claim 1, wherein: initial values of the carbon source: a is more than or equal to 16 and less than or equal to 162.5, and the initial value of the silicon source is as follows: a' is more than or equal to 40 and less than or equal to 250, and the carbon-silicon ratio during the growth of the buffer layer is ensured to be between 0.8 and 1.3.

3. A method of controlling epitaxial growth of silicon carbide according to claim 1, wherein: end value of the carbon source: b is more than or equal to 125 and less than or equal to 480, and the ending value of the silicon source is as follows: b' is more than or equal to 250 and less than or equal to 600, and the carbon-silicon ratio during the growth of the epitaxial layer is ensured to be between 1.0 and 1.6.

4. A method of controlling epitaxial growth of silicon carbide according to claim 1, wherein: during the sectional control method, the carbon-silicon ratio is between 0.8 and 1.6.

5. A method of controlling epitaxial growth of silicon carbide according to claim 1, wherein: the time T is 10-600 s, and the number k of the sections is 2-200.

6. A method of controlling epitaxial growth of silicon carbide according to claim 5, wherein: the time T is between 40 and 200s, and the number k of the sections is between 5 and 20.

7. A method of controlling epitaxial growth of silicon carbide according to claim 1, wherein: the carbon source is ethylene or propane, and the silicon source is trichlorosilane or silane.

8. A method of controlling epitaxial growth of silicon carbide according to claim 1, wherein: and the flow rate of the carbon source and the silicon source is gradually changed by the sectional control method, so that the flow rate change speed of the carbon source and the silicon source is gradually increased, and the change speed of the carbon-silicon ratio is gradually increased, so as to reduce the growth thickness of a transition layer in the flow rate change process.

9. A silicon carbide epitaxial wafer produced by the method for controlling epitaxial growth of silicon carbide according to any one of claims 1 to 8, characterized in that: the surface roughness Rq of the silicon carbide epitaxial wafer is less than 0.15 nm.

10. The method of claim 9The silicon carbide epitaxial wafer is characterized in that: the method is characterized in that: the surface fatal defect density of the silicon carbide epitaxial wafer is less than 0.3/cm²The surface critical defects include triangles, carrots and drop defects.