阅读说明：本技术 一种降低氮掺杂整体不均匀性的n型碳化硅晶体的生长方法 (Growth method of n-type silicon carbide crystal for reducing nitrogen doping integral nonuniformity ) 是由 不公告发明人 于 2021-08-25 设计创作，主要内容包括：一种降低氮掺杂整体不均匀性的n型碳化硅晶体的生长方法,它属于碳化硅晶体生长技术领域。本发明要解决的技术问题为晶体生长中掺杂的均匀性。本发明在坩埚中填入碳化硅粉料并安装碳化硅籽晶,将坩埚放入晶体生长炉中,将晶体生长炉抽真空到10～(-5)-10～(-9)atm,加热到500-1200℃,维持0.5-2h,将晶体生长炉充入氩气、氮气、氢气的混合气体继续加热晶体生长炉到2100-2400℃,然后控制生长过程中通入气体中氮气所占体积比随时间逐渐提高,生长晶体40-150h,然后充入氮气关闭加热电源后随炉冷却至室温,完成降低氮掺杂整体不均匀性的n型碳化硅晶体的生长。本发明制备的晶体均匀度高。(A growth method of n-type silicon carbide crystals for reducing nitrogen doping integral nonuniformity belongs to the technical field of silicon carbide crystal growth. The technical problem to be solved by the invention is the uniformity of doping in crystal growth. The invention fills silicon carbide powder in a crucible, installs silicon carbide seed crystals, puts the crucible into a crystal growth furnace, and vacuums the crystal growth furnace to 10 ‑5 ‑10 ‑9 and atm, heating to 500-1200 ℃, maintaining for 0.5-2h, filling the mixed gas of argon, nitrogen and hydrogen into the crystal growth furnace, continuously heating the crystal growth furnace to 2100-2400 ℃, then controlling the volume ratio of the nitrogen in the gas filled in the growth process to gradually increase along with time to grow the crystal for 40-150h, then filling nitrogen, closing a heating power supply, cooling to room temperature along with the furnace, and finishing the growth of the n-type silicon carbide crystal for reducing the integral non-uniformity of nitrogen doping. The crystal prepared by the invention has high uniformity.)

1. A method for growing an n-type silicon carbide crystal to reduce nitrogen doping bulk non-uniformity, comprising: the method comprises the following steps:

step 1, filling silicon carbide powder into a crucible, installing silicon carbide seed crystals, and putting the crucible into a crystal growth furnace for later use;

step 2, vacuumizing the crystal growth furnace to 10 DEG^-5-10^-9atm, heating to 500-1200 deg.C, maintaining for 0.5-2 h;

step 3, filling the mixed gas of argon, nitrogen and hydrogen into the crystal growth furnace in the step 2 to 10^-2-10^-4atm, wherein the volume ratio of the nitrogen is 5-40%, the volume ratio of the hydrogen is 1-10%, and the balance is argon, the crystal growth furnace is continuously heated to 2100-2400 ℃, then the volume ratio of the nitrogen in the introduced gas in the growth process is controlled to be gradually increased along with the time, and the crystal is grown for 40-150 h;

and 4, filling nitrogen to 300-.

2. The method of claim 1, wherein the silicon carbide crystal growth step comprises: the purity of the silicon carbide powder in the step 1 is 99.999%.

3. A method for growing a silicon carbide crystal of n-type with reduced nitrogen doping bulk non-uniformity according to claim 1 or 2, wherein: in the step 1, the silicon carbide seed crystal is arranged on the inner side of the upper cover of the crucible.

4. The method of claim 3, wherein the silicon carbide crystal growth step comprises: crucible growth furnace in step 2Vacuum pumping is carried out to 10^-5atm, heating to 800 deg.C, and maintaining for 1 h.

5. The method of claim 4, wherein the silicon carbide crystal growth step comprises: introducing the mixed gas of argon, nitrogen and hydrogen to 10 in the step 3^-3atm, wherein the volume ratio of nitrogen is 10%, the volume ratio of hydrogen is 1%, the balance is argon, and the total flow of introduced gas is 1000 sccm.

6. The method of claim 5, wherein the silicon carbide crystal growth step comprises: and 3, dividing the volume ratio of the nitrogen in the introduced gas in the growth process into 3-9 times according to the equal proportion of the total time length, wherein the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time number, and the volume ratio of the nitrogen is 1.01-1.5 times of the initial volume ratio at the end of growth.

7. The method of claim 6, wherein the silicon carbide crystal growth step comprises: and 3, dividing the volume ratio of the nitrogen in the introduced gas in the growth process into 5 times according to the equal proportion of the total time length, wherein the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time times, and the volume ratio of the nitrogen is 1.05 times of the initial volume ratio at the end of growth.

8. The method of claim 6, wherein the silicon carbide crystal growth step comprises: and 3, dividing the volume ratio of the nitrogen in the introduced gas in the growth process into 9 times according to the equal proportion of the total time length, wherein the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time times, and the volume ratio of the nitrogen is 1.5 times of the initial volume ratio at the end of growth.

9. The method of claim 6, wherein the silicon carbide crystal growth step comprises: and 3, dividing the volume ratio of the nitrogen in the introduced gas in the growth process into 6 times according to the equal proportion of the total time length, wherein the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time times, and the volume ratio of the nitrogen is 1.2 times of the initial volume ratio at the end of growth.

10. The method of claim 6, wherein the silicon carbide crystal growth step comprises: and 3, dividing the volume ratio of the nitrogen in the introduced gas in the growth process into 4 times according to the equal proportion of the total time length, wherein the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time times, and the volume ratio of the nitrogen is 1.2 times of the initial volume ratio at the end of growth.

Technical Field

The invention belongs to the technical field of silicon carbide crystal growth; in particular to a growth method of an n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping.

Background

The silicon carbide as the third-generation semiconductor material has the characteristics of wide forbidden band, high breakdown field strength, high thermal conductivity and the like. The method can be applied to the fields of new energy automobiles, photovoltaic inverters, charging piles and the like to achieve the aims of reducing power consumption, improving switching frequency, reducing overall cost and the like.

Since silicon carbide is decomposed at normal pressure before it is heated to its melting point, silicon-like silicon cannot be used as it isA method for crystal growth. At present, the growth method of large-size silicon carbide crystals is mainly a PVT method, and the method comprises the steps of putting silicon carbide powder into the bottom of a crucible, adhering silicon carbide seed crystals (silicon carbide single crystal wafers serving as crystal growth seeds) to the top of the crucible, and vacuumizing a reaction container to 10 DEG^-5-10^-9atm, and heating to about 1000 deg.C while maintaining vacuum degree. Then, a proper amount of argon gas is filled into the reactor to 10^-2-10^-4Further heating to about 2000 deg.C, decomposing the raw material at the high temperature and in inert atmosphere, and depositing the gas phase generated after decomposition onto the seed crystal under the control of temperature gradient to grow crystal.

Due to the different requirements of silicon carbide in device design, substrates currently prepared from grown crystals can be classified into semi-insulating and conductive types. And the conductive type silicon carbide substrate may be classified into an n-type and a p-type according to the doping element used. The doping element commonly used in the n-type silicon carbide substrate is nitrogen, and the doping mode is generally that a certain partial pressure of nitrogen is added into the atmosphere in the crystal growth process, so that nitrogen atoms enter the crystal in the crystal growth process.

In the process of silicon carbide pyrolysis, carbon atoms and silicon atoms are not in the proportion of 1: the ratio of 1 is introduced into the gas phase, wherein silicon atoms are more easily introduced into the gas phase, so that the residual powder has more carbon elements and graphitization phenomenon. The ratio of the number of carbon atoms to the number of silicon atoms in the gas phase is called the carbon-silicon ratio, depends on the temperature, the morphology of the powder, the properties of the crucible and the like, and has an influence on the growth rate of the silicon carbide crystal and the density of defects, and also has an influence on the doping effect. For nitrogen element, when the ratio of nitrogen in the atmosphere is constant, the relative doping effect is poor when the carbon silicon ratio is high, and the doping effect is good when the carbon silicon ratio is low.

During the growth process, silicon atoms are easier to enter a gas phase than carbon atoms, and the silicon atoms can leak out of the growth cavity from the crucible gap, so that the carbon-silicon ratio in the crucible can be gradually improved along with the growth of the crystal. Generally, when a nitrogen-doped n-type conductive silicon carbide substrate is prepared, the partial pressure of nitrogen is constant, and the nitrogen doping concentration is reduced to a certain extent due to the gradual increase of the carbon-silicon ratio, so that the nitrogen concentration in a crystal grown at the later stage of crystal growth is lower than that in a crystal grown before, and the corresponding electrical properties such as conductivity are different. Meanwhile, the distribution of the carbon-silicon ratio in the reaction chamber is not uniform in the growth process due to the material exchange effect of the gas phase and the powder and the graphite crucible wall. For the growth surface along the radial direction of the crystal, the carbon-silicon ratio is lower in the middle part, and the carbon-silicon ratio is higher in the periphery because of more carbon elements in the gas phase due to the material exchange with the adjacent graphite crucible wall. The radial carbon-silicon ratio uneven distribution also causes a certain difference between the doping concentration and the conductivity of nitrogen elements along the radial direction of the silicon carbide crystal.

Disclosure of Invention

The invention aims to provide a method for growing an n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping.

The invention is realized by the following technical scheme:

a method for growing an n-type silicon carbide crystal with reduced nitrogen doping bulk non-uniformity, comprising the steps of:

step 1, filling silicon carbide powder into a crucible, installing silicon carbide seed crystals, and putting the crucible into a crystal growth furnace for later use;

step 2, vacuumizing the crystal growth furnace to 10 DEG^-5-10^-9atm, heating to 500-1200 deg.C, maintaining for 0.5-2 h;

step 3, filling the mixed gas of argon, nitrogen and hydrogen into the crystal growth furnace in the step 2 to 10^-2-10^-4atm, wherein the volume ratio of the nitrogen is 5-40%, the volume ratio of the hydrogen is 1-10%, and the balance is argon, the crystal growth furnace is continuously heated to 2100-2400 ℃, then the volume ratio of the nitrogen in the introduced gas in the growth process is controlled to be gradually increased along with the time, and the crystal is grown for 40-150 h;

and 4, filling nitrogen to 300-.

According to the method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, the purity of the silicon carbide powder in the step 1 is 99.999%.

The invention relates to a method for growing an n-type silicon carbide crystal for reducing the overall nonuniformity of nitrogen doping.

The invention relates to a method for growing an n-type silicon carbide crystal for reducing the overall nonuniformity of nitrogen doping, wherein a crucible growing furnace in the step 2 is vacuumized to 10 DEG^-5atm, heating to 800 deg.C, and maintaining for 1 h.

The invention relates to a growth method of an n-type silicon carbide crystal for reducing nitrogen-doped integral nonuniformity, which is characterized in that mixed gas of argon, nitrogen and hydrogen is introduced to 10 in step 3^-3atm, wherein the volume ratio of nitrogen is 10%, the volume ratio of hydrogen is 1%, the balance is argon, and the total flow of introduced gas is 1000 sccm.

According to the growth method of the n-type silicon carbide crystal for reducing the nitrogen doping integral nonuniformity, the volume ratio of nitrogen in introduced gas in the growth process in the step 3 is divided into 3-9 times according to the equal proportion of the total time, the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time times, and the volume ratio of the nitrogen at the end of growth is 1.01-1.5 times of the initial volume ratio.

According to the growth method of the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, in the step 3, the volume ratio of nitrogen in introduced gas is divided into 5 times according to the equal proportion of the total time length in the growth process, the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time times, and the volume ratio of the nitrogen is 1.05 times of the initial volume ratio at the end of growth.

According to the growth method of the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, in the step 3, the volume ratio of nitrogen in introduced gas is divided into 9 times according to the equal proportion of the total time length in the growth process, the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time times, and the volume ratio of the nitrogen is 1.5 times of the initial volume ratio at the end of growth.

According to the growth method of the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, in the step 3, the volume ratio of nitrogen in introduced gas in the growth process is divided into 6 times according to the equal proportion of the total time length, the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time times, and the volume ratio of the nitrogen at the end of growth is 1.2 times of the initial volume ratio.

According to the growth method of the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, in the step 3, the volume ratio of nitrogen in introduced gas in the growth process is divided into 4 times according to the equal proportion of the total time length, the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time times, and the volume ratio of the nitrogen is 1.2 times of the initial volume ratio at the end of growth.

According to the growth method of the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, a proper amount of hydrogen is added into the doping atmosphere of the PVT method, and the hydrogen and silicon carbide powder are utilized to generate hydrocarbon and silicon hydride. As carbon atoms are easier to enter the gas phase in the process of forming the gas phase by the reaction of the hydrogen and the silicon carbide powder, the carbon-silicon ratio of the generated gas phase can be increased, and the reaction of the gas phase and the wall of the graphite crucible is further inhibited, and the radial unevenness of the carbon-silicon ratio caused by the reaction is reduced. Although this process suppresses the doping of nitrogen to some extent, the radial nonuniformity of the nitrogen doping concentration can be reduced while satisfying the nitrogen doping concentration requirement by adjusting the gas ratio.

The invention relates to a growth method of an n-type silicon carbide crystal for reducing nitrogen doping integral nonuniformity, which simultaneously uses different nitrogen partial pressures in different periods of crystal growth to reduce the inconsistency of nitrogen doping concentration in the growing silicon carbide crystal caused by the change of carbon-silicon ratio caused by the crystal growth and powder change.

Detailed Description

The first embodiment is as follows:

a method for growing an n-type silicon carbide crystal with reduced nitrogen doping bulk non-uniformity, comprising the steps of:

step 1, filling silicon carbide powder into a crucible, installing silicon carbide seed crystals, and putting the crucible into a crystal growth furnace for later use;

step 2, vacuumizing the crystal growth furnace to 10 DEG^-5atm, heating to 800 ℃, and maintaining for 1 h;

step 3, filling the mixed gas of argon, nitrogen and hydrogen into the crystal growth furnace in the step 2 to 10^-3atm, wherein the volume ratio of nitrogen is 10 percent, the volume ratio of hydrogen is 1 percent, and the balance is argon, continuously heating the crystal growth furnace to 2200 ℃, and then controlling the volume ratio of nitrogen in the introduced gas to gradually increase along with time in the growth process to grow the crystal for 80 hours;

and 4, filling nitrogen to 500torr, cooling to 800 ℃ at the speed of 5 ℃/min, turning off a heating power supply, and cooling to room temperature along with the furnace to finish the growth of the n-type silicon carbide crystal for reducing the integral non-uniformity of nitrogen doping.

In the method for growing n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping in this embodiment, the purity of the silicon carbide powder in step 1 is 99.999%.

In the method for growing an n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping according to this embodiment, in step 1, a silicon carbide seed crystal is installed inside the upper cover of a crucible.

In the method for growing an n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping in the present embodiment, the total flow rate of the gas introduced in step 3 is 1000 sccm.

In the method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, in the step 3, the volume ratio of the nitrogen gas in the introduced gas is divided into 5 times according to the equal proportion of the total time length, the volume ratio of the nitrogen gas increased each time is the total increase divided by the divided time times, and the volume ratio of the nitrogen gas is 1.05 times of the initial volume ratio at the end of growth.

The properties of the silicon carbide crystal prepared by the method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping in the embodiment are shown in table 1:

TABLE 1 silicon carbide crystal resistivity

In the method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, the comparative example is that silicon carbide powder is filled in a crucible, silicon carbide seed crystals are installed, the crucible is placed in a crystal growth furnace and is vacuumized to 10 DEG^-5atm, heating to 800 deg.C, maintaining for 1 hr, and introducing mixed gas of argon and nitrogen to 10 deg.C^-3atm, nitrogen occupies 0.1 volume ratio, and the total flow of the introduced gas is 1000 sccm. Heating is continued to 2200 ℃, crystals begin to grow, and the growth lasts for 80 h. The silicon carbide crystal properties of the comparative example are shown in table 2:

TABLE 2 comparative example silicon carbide crystal Properties

The conductivity of the crystal can be used as a measure of the doping concentration of nitrogen, and a better conductivity indicates a higher concentration of nitrogen doping. The above crystals were prepared as substrates and tested for resistivity at different positions in the axial direction. As can be seen from tables 1 and 2, the crystal prepared according to the first embodiment has a smaller range of resistivity, and since the resistivity is proportional to the concentration of nitrogen, the doping concentration of nitrogen at each position of the crystal is in a smaller range.

In the method for growing an n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping according to the present embodiment, a proper amount of hydrogen gas is added into the doping atmosphere of the PVT method, and the hydrogen gas and the silicon carbide powder are used to generate hydrocarbons and silicon hydride. As carbon atoms are easier to enter the gas phase in the process of forming the gas phase by the reaction of the hydrogen and the silicon carbide powder, the carbon-silicon ratio of the generated gas phase can be increased, and the reaction of the gas phase and the wall of the graphite crucible is further inhibited, and the radial unevenness of the carbon-silicon ratio caused by the reaction is reduced. Although this process suppresses the doping of nitrogen to some extent, the radial nonuniformity of the nitrogen doping concentration can be reduced while satisfying the nitrogen doping concentration requirement by adjusting the gas ratio.

The method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping reduces the front and back non-uniformity of nitrogen doping concentration in the grown silicon carbide crystal caused by the change of carbon-silicon ratio caused by the change of powder due to crystal growth by using different nitrogen partial pressures in different periods of crystal growth.

The second embodiment is as follows:

a method for growing an n-type silicon carbide crystal with reduced nitrogen doping bulk non-uniformity, comprising the steps of:

step 1, filling silicon carbide powder into a crucible, installing silicon carbide seed crystals, and putting the crucible into a crystal growth furnace for later use;

step 2, vacuumizing the crystal growth furnace to 10 DEG^-5-10^-9atm, heating to 1000 deg.C, maintaining for 2 h;

step 3, filling the mixed gas of argon, nitrogen and hydrogen into the crystal growth furnace in the step 2 to 10^-4atm, wherein the volume ratio of the nitrogen is 20 percent, the volume ratio of the hydrogen is 2 percent, and the balance is argon, the crystal growth furnace is continuously heated to 2100 ℃, then the volume ratio of the nitrogen in the introduced gas is gradually increased along with the time in the growth process, and the crystal is grown for 100 hours;

and 4, filling nitrogen to 300torr, cooling to 800 ℃ at the speed of 8 ℃/min, turning off a heating power supply, and cooling to room temperature along with the furnace to finish the growth of the n-type silicon carbide crystal for reducing the integral non-uniformity of nitrogen doping.

In the method for growing n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping in this embodiment, the purity of the silicon carbide powder in step 1 is 99.999%.

In the method for growing an n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping according to this embodiment, in step 1, a silicon carbide seed crystal is installed inside the upper cover of a crucible.

In the method for growing an n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping in the present embodiment, the total flow rate of the gas introduced in step 3 is 1000 sccm.

In the method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, the volume ratio of the nitrogen in the introduced gas in the growth process in the step 3 is divided into 9 times according to the equal proportion of the total time length, the volume ratio of the nitrogen increased each time is the total increased amount divided by the divided time times, and the volume ratio of the nitrogen at the end of growth is 1.5 times of the initial volume ratio.

In the method for growing an n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping according to the present embodiment, a proper amount of hydrogen gas is added into the doping atmosphere of the PVT method, and the hydrogen gas and the silicon carbide powder are used to generate hydrocarbons and silicon hydride. As carbon atoms are easier to enter the gas phase in the process of forming the gas phase by the reaction of the hydrogen and the silicon carbide powder, the carbon-silicon ratio of the generated gas phase can be increased, and the reaction of the gas phase and the wall of the graphite crucible is further inhibited, and the radial unevenness of the carbon-silicon ratio caused by the reaction is reduced. Although this process suppresses the doping of nitrogen to some extent, the radial nonuniformity of the nitrogen doping concentration can be reduced while satisfying the nitrogen doping concentration requirement by adjusting the gas ratio.

The method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping reduces the front and back non-uniformity of nitrogen doping concentration in the grown silicon carbide crystal caused by the change of carbon-silicon ratio caused by the change of powder due to crystal growth by using different nitrogen partial pressures in different periods of crystal growth.

The third concrete implementation mode:

a method for growing an n-type silicon carbide crystal with reduced nitrogen doping bulk non-uniformity, comprising the steps of:

step 1, filling silicon carbide powder into a crucible, installing silicon carbide seed crystals, and putting the crucible into a crystal growth furnace for later use;

step 2, vacuumizing the crystal growth furnace to 10 DEG^-5atm, heating to 900 deg.C, maintaining for 0.5 h;

step 3Filling the crystal growth furnace in the step 2 with mixed gas of argon, nitrogen and hydrogen to 10^-2atm, wherein the volume ratio of nitrogen is 10 percent, the volume ratio of hydrogen is 1 percent, and the balance is argon, continuously heating the crystal growth furnace to 2400 ℃, and then controlling the volume ratio of nitrogen in the introduced gas to gradually increase along with the time in the growth process to grow the crystal for 100 hours;

and 4, filling nitrogen to 400torr, cooling to 800 ℃ at the speed of 8 ℃/min, turning off a heating power supply, and cooling to room temperature along with the furnace to finish the growth of the n-type silicon carbide crystal for reducing the integral non-uniformity of nitrogen doping.

In the method for growing n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping in this embodiment, the purity of the silicon carbide powder in step 1 is 99.999%.

In the method for growing an n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping according to this embodiment, in step 1, a silicon carbide seed crystal is installed inside the upper cover of a crucible.

In the method for growing an n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping in the present embodiment, the total flow rate of the gas introduced in step 3 is 1000 sccm.

In the method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, in the step 3, the volume ratio of the nitrogen gas in the introduced gas is divided into 6 times according to the equal proportion of the total duration, the volume ratio of the nitrogen gas increased each time is the total increase divided by the divided time times, and the volume ratio of the nitrogen gas is 1.2 times of the initial volume ratio at the end of growth.

In the method for growing an n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping according to the present embodiment, a proper amount of hydrogen gas is added into the doping atmosphere of the PVT method, and the hydrogen gas and the silicon carbide powder are used to generate hydrocarbons and silicon hydride. As carbon atoms are easier to enter the gas phase in the process of forming the gas phase by the reaction of the hydrogen and the silicon carbide powder, the carbon-silicon ratio of the generated gas phase can be increased, and the reaction of the gas phase and the wall of the graphite crucible is further inhibited, and the radial unevenness of the carbon-silicon ratio caused by the reaction is reduced. Although this process suppresses the doping of nitrogen to some extent, the radial nonuniformity of the nitrogen doping concentration can be reduced while satisfying the nitrogen doping concentration requirement by adjusting the gas ratio.

The method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping reduces the front and back non-uniformity of nitrogen doping concentration in the grown silicon carbide crystal caused by the change of carbon-silicon ratio caused by the change of powder due to crystal growth by using different nitrogen partial pressures in different periods of crystal growth.

The fourth concrete implementation mode:

a method for growing an n-type silicon carbide crystal with reduced nitrogen doping bulk non-uniformity, comprising the steps of:

step 1, filling silicon carbide powder into a crucible, installing silicon carbide seed crystals, and putting the crucible into a crystal growth furnace for later use;

step 2, vacuumizing the crystal growth furnace to 10 DEG^-5-10^-9atm, heating to 500-1200 deg.C, maintaining for 0.5-2 h;

step 3, filling the mixed gas of argon, nitrogen and hydrogen into the crystal growth furnace in the step 2 to 10^-2-10^-4atm, wherein the volume ratio of the nitrogen is 5-40%, the volume ratio of the hydrogen is 1-10%, and the balance is argon, the crystal growth furnace is continuously heated to 2100-2400 ℃, then the volume ratio of the nitrogen in the introduced gas in the growth process is controlled to be gradually increased along with the time, and the crystal is grown for 40-150 h;

and 4, filling nitrogen to 300-.

In the method for growing an n-type silicon carbide crystal to reduce the overall non-uniformity of nitrogen doping according to the present embodiment, a proper amount of hydrogen gas is added into the doping atmosphere of the PVT method, and the hydrogen gas and the silicon carbide powder are used to generate hydrocarbons and silicon hydride. As carbon atoms are easier to enter the gas phase in the process of forming the gas phase by the reaction of the hydrogen and the silicon carbide powder, the carbon-silicon ratio of the generated gas phase can be increased, and the reaction of the gas phase and the wall of the graphite crucible is further inhibited, and the radial unevenness of the carbon-silicon ratio caused by the reaction is reduced. Although this process suppresses the doping of nitrogen to some extent, the radial nonuniformity of the nitrogen doping concentration can be reduced while satisfying the nitrogen doping concentration requirement by adjusting the gas ratio.

The method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping reduces the front and back non-uniformity of nitrogen doping concentration in the grown silicon carbide crystal caused by the change of carbon-silicon ratio caused by the change of powder due to crystal growth by using different nitrogen partial pressures in different periods of crystal growth.

The fifth concrete implementation mode:

according to the method for growing the n-type silicon carbide crystal for reducing the nitrogen doping overall nonuniformity, the purity of the silicon carbide powder in the step 1 is 99.999%.

The sixth specific implementation mode:

according to the method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, in step 1, a silicon carbide seed crystal is arranged on the inner side of the upper cover of the crucible.

The seventh embodiment:

according to the fourth embodiment of the method for growing the n-type silicon carbide crystal for reducing the overall non-uniformity of nitrogen doping, the crucible growing furnace in the step 2 is vacuumized to 10 DEG^-5atm, heating to 800 deg.C, and maintaining for 1 h.

The specific implementation mode is eight:

according to the fourth specific embodiment, in the method for growing the n-type silicon carbide crystal for reducing the nitrogen doping integral nonuniformity, the mixed gas of argon, nitrogen and hydrogen is introduced to 10 degrees in the step 3^-3atm, wherein the volume ratio of nitrogen is 10%, the volume ratio of hydrogen is 1%, the balance is argon, and the total flow of introduced gas is 1000 sccm.

The specific implementation method nine:

according to a fourth specific embodiment, in the step 3, the volume ratio of the nitrogen gas in the introduced gas is divided into 3-9 times according to the equal proportion of the total time length in the growing process, the volume ratio of the nitrogen gas increased each time is the total increase divided by the divided time times, and the volume ratio of the nitrogen gas is 1.01-1.5 times of the initial volume ratio at the end of the growth.

The detailed implementation mode is ten:

according to a fourth specific embodiment, in the step 3, the volume ratio of the nitrogen gas in the introduced gas is divided into 5 times according to the equal proportion of the total time length, the volume ratio of the nitrogen gas increased each time is the total increase divided by the divided time number, and the volume ratio of the nitrogen gas at the end of growth is 1.05 times of the initial volume ratio.

The concrete implementation mode eleven:

according to a fourth specific embodiment, in the step 3, the volume ratio of the nitrogen gas in the introduced gas is divided into 9 times according to the equal proportion of the total time length, the volume ratio of the nitrogen gas increased each time is the total increase divided by the divided time times, and the volume ratio of the nitrogen gas at the end of growth is 1.5 times of the initial volume ratio.

The specific implementation mode twelve:

according to a fourth specific embodiment, in the step 3, the volume ratio of the nitrogen gas in the introduced gas is divided into 6 times according to the equal proportion of the total time length, the volume ratio of the nitrogen gas increased each time is the total increase divided by the divided time number, and the volume ratio of the nitrogen gas at the end of growth is 1.2 times of the initial volume ratio.

The specific implementation mode is thirteen:

according to a fourth specific embodiment, in the step 3, the volume ratio of the nitrogen gas in the introduced gas is divided into 4 times according to the equal proportion of the total time length, the volume ratio of the nitrogen gas increased each time is the total increase divided by the divided time number, and the volume ratio of the nitrogen gas at the end of growth is 1.2 times of the initial volume ratio.