1. A method for adding powder of an additional carbon source in growth of silicon carbide crystals by a PVT method is characterized by comprising the following steps: the method comprises the following steps:

step 1, respectively preparing three different powder materials, wherein the first powder material is pure silicon carbide powder material, the second powder material is uniformly mixed silicon carbide powder material added with 10-30 wt% of active carbon powder, and the third powder material is uniformly mixed silicon carbide powder material added with 1-30 wt% of active carbon powder;

step 2, dividing a powder adding area in the crucible into a first powder adding area (1), a second powder adding area (2) and a third powder adding area (3), setting the height of the crucible powder adding area as h and the radius as r, wherein the height of the second powder adding area (2) is 0.1-0.8 h and the radius is 0.05-0.8r, the height of the third powder adding area (3) is 0.05-0.15h and the radius is r, and the rest of the space is the first powder adding area (1);

and 3, adding a certain mass of first powder to the bottom of the crucible, inserting a cylinder which has the same volume as the second powder adding area (2) and is not provided with an upper bottom and a lower bottom into the center of the crucible, adding the second powder into the cylinder, adding the rest of the first powder into a gap between the cylinder and the crucible, carefully taking out the cylinder, and adding the third powder to complete the addition of the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method.

2. The method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method according to claim 1, wherein the method comprises the following steps: in the step 1, the activated carbon powder in the second powder is high-purity amorphous carbon powder or graphite powder with the particle size of 100-1000 μm.

3. The method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method according to claim 2, wherein the method comprises the following steps: in the step 1, the activated carbon powder in the second powder is high-purity amorphous carbon powder with the particle size of 500 mu m and the addition amount of 15 wt%.

4. The method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method according to claim 1, wherein the method comprises the following steps: in the step 1, the activated carbon powder in the third powder is high-purity amorphous carbon powder or graphite powder, and the particle size is 100-1000 μm.

5. The method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method according to claim 4, wherein the method comprises the following steps: in the step 1, the activated carbon powder in the third powder is high-purity amorphous carbon powder with the particle size of 800 microns and the addition amount of 10 wt%.

6. The method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method according to claim 2 or 4, wherein the method comprises the following steps: in the step 2, the height of the second powder adding area (2) is 0.6h, the radius is 0.5r, and the height of the third powder adding area (3) is 0.1h, and the radius is r.

7. The method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method according to claim 6, wherein the method comprises the following steps: the mass ratio of the first powder material, the second powder material and the third powder material in the step 3 is 1875-2000:375-450: 250-350.

8. The method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method according to claim 6, wherein the method comprises the following steps: in the step 3, the mass ratio of the first powder to the second powder to the third powder is 1875:375: 250.

9. The method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method according to claim 8, wherein the method comprises the following steps: adhering seed crystal on the crucible cover, then putting the whole crucible with the powder of the additional carbon source into a crystal growth furnace to start crystal growth, wherein the growth condition used in the growth process is 10^-3atm argon atmosphere, growth temperature 2300 deg.C, growth time 80 h.

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 before being heated to a melting point under normal pressure, a method similar to the growth of silicon crystal cannot be directly used. 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^-2-10^-5atm, 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^-1-10^-5Further 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.

In the growth process of silicon carbide crystal in a general thermal field mode, sublimation and recrystallization of silicon carbide powder at the bottom of a crucible due to the structure and material transportation of a thermal field can make the silicon carbide powder gradually form three different areas, and the schematic diagram is shown in fig. 2: the 1 region is a graphitized region, the temperature of the region close to the crucible wall is higher, so that more silicon carbide powder is decomposed, the silicon carbide powder is a main region for generating gas-phase components, carbon atoms and silicon atoms do not enter the gas phase at equal molar ratio in the decomposition process, the content of silicon in the gas-phase components is higher, and the powder gradually has graphitization phenomenon due to carbon deposition; the 2 area is a nucleus formed by oriented arrangement of crystal grains formed by recrystallization in the middle, and the gas phase substance conveyed from the 1 area can generate certain substance exchange with the nucleus in the area; the region 3 is a disk structure formed by recrystallization and in which needle-shaped grains are directionally arranged, the density is higher than that of the region 2, and the material exchange between a gas phase and a solid phase can also occur in the region; the arrows in the figure indicate the direction of gas phase species transport. The carbon-silicon ratio mentioned in the above process is an important control condition in the crystal growth process, and when the carbon-silicon ratio is low, there is not enough carbon atoms supplied for the crystal growth, so that the growth rate is slowed down, and the defects are increased due to the change of the carbon-silicon ratio.

At present, the ratio of carbon to silicon in gas phase is improved by adding activated carbon powder into powder so as to improve and maintain the growth rate of silicon carbide crystals, and meanwhile, the unstable change of a thermal field caused by the change of the thermal conductivity coefficient due to the consumption of a graphite crucible is reduced. However, in the above-mentioned region 1, the activated carbon powder is difficult to react with the silicon component in the gas phase due to the higher temperature, so that the effect of the activated carbon powder in the region for improving the carbon-silicon ratio is poor, and meanwhile, the activated carbon powder can occupy the volume of the original silicon carbide powder to a certain extent, and the amount of the silicon carbide crystal grown in the primary crystal growth process can also be reduced to a certain extent. It is not reasonable to add activated carbon powder in the 1 region in combination.

Disclosure of Invention

The invention aims to provide a method for adding powder of an additional carbon source in growth of PVT method silicon carbide crystals, which can optimize crystal growth.

The invention is realized by the following technical scheme:

a method for adding powder of an additional carbon source in growth of silicon carbide crystals by a PVT method comprises the following steps:

step 1, respectively preparing three different powder materials, wherein the first powder material is pure silicon carbide powder material, the second powder material is uniformly mixed silicon carbide powder material added with 10-30 wt% of active carbon powder, and the third powder material is uniformly mixed silicon carbide powder material added with 1-30 wt% of active carbon powder;

step 2, dividing a powder adding area in the crucible into a first powder adding area, a second powder adding area and a third powder adding area, setting the height of the crucible powder adding area as h and the radius as r, wherein the height of the second powder adding area is 0.1-0.8 h and the radius as 0.05-0.8r, the height of the third powder adding area is 0.05-0.15h and the radius as r, and the rest space is the first powder adding area;

and 3, adding a certain mass of first powder to the bottom of the crucible, inserting a cylinder which has the same volume as a second powder adding area and does not have an upper bottom and a lower bottom into the center of the crucible, adding the second powder into the cylinder, adding the rest of the first powder into a gap between the cylinder and the crucible, carefully taking out the cylinder, and adding a third powder to complete the addition of the powder with the carbon source in the growth of the silicon carbide crystal by the PVT method.

According to the method for adding the powder material of the additional carbon source in the growth of the PVT method silicon carbide crystal, in the step 1, the activated carbon powder in the second powder material is high-purity amorphous carbon powder or graphite powder, and the particle size is 100-1000 mu m.

The invention relates to a method for adding powder of an additional carbon source in growth of a PVT method silicon carbide crystal, in the step 1, the activated carbon powder in the second powder is high-purity amorphous carbon powder, the particle size is 500 mu m, and the addition amount is 15 wt%.

According to the method for adding the powder material of the additional carbon source in the growth of the PVT method silicon carbide crystal, in the step 1, the activated carbon powder in the third powder material is high-purity amorphous carbon powder or graphite powder, and the particle size is 100-1000 mu m.

According to the method for adding the powder of the additional carbon source in the growth of the PVT method silicon carbide crystal, the activated carbon powder in the third powder in the step 1 is high-purity amorphous carbon powder, the particle size is 800 micrometers, and the adding amount is 10 wt%.

According to the method for adding the powder for adding the carbon source in the growth of the silicon carbide crystal by the PVT method, in the step 2, the height of a second powder adding area is 0.6h, the radius is 0.5r, and the height of a third powder adding area is 0.1h, and the radius is r.

The method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method comprises the step 3, wherein the mass ratio of the first powder to the second powder to the third powder is 1875-2000:375-450: 250-350.

According to the method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method, the mass ratio of the first powder, the second powder and the third powder in the step 3 is 1875:375: 250.

The invention relates to a method for adding powder of an additional carbon source in growth of a PVT method silicon carbide crystal, which comprises the steps of adhering seed crystals on a crucible cover, then putting the whole crucible with the powder of the additional carbon source into a crystal growth furnace to start crystal growth, wherein the growth condition used in the growth process is 10^-3atm argon atmosphere, growth temperature 2300 deg.C, growth time 80 h.

According to the method for adding the powder of the additional carbon source in the growth of the PVT method silicon carbide crystal, when the powder is added into the crucible, high-purity carbon powder is added into the areas 2 and 3 formed by sublimation and recrystallization in the corresponding growth process. The gas phase enters the growth cavity in the sequence of 1 region to 2 regions and then to 3 regions in the growth process. In the process, the material exchange reaction of the gas phase and the solid phase flowing through the 2 area and the 3 area is utilized to improve the carbon-silicon ratio in the gas phase, improve and maintain the growth rate of the silicon carbide crystal, and simultaneously reduce the unstable change of a thermal field caused by the change of the thermal conductivity coefficient due to the consumption of the graphite crucible. Compared with the method of adding high-purity carbon powder in all the areas, the method removes the unreasonable addition of the area 1, reserves the reasonable addition of the areas 2 and 3, and improves the growth amount of the silicon carbide crystal compared with the original method.

Compared with a method of adding carbon powder into powder in all areas, the method for adding the powder with the additional carbon source in the growth of the PVT method silicon carbide crystal can improve the total mass of the grown crystal, maintain the capability of improving the carbon-silicon ratio and reducing the generation of defects.

Drawings

FIG. 1 is a schematic structural diagram of an addition region of a method for adding powder of an additional carbon source in the growth of silicon carbide crystals by a PVT method;

FIG. 2 is a schematic diagram of three different regions formed by silicon carbide powder gradually due to sublimation and recrystallization caused by thermal field structure and material transportation in the growth of silicon carbide crystals by a conventional PVT method.

Detailed Description

The first embodiment is as follows:

a method for adding powder of an additional carbon source in growth of silicon carbide crystals by a PVT method comprises the following steps:

step 1, respectively preparing three different powder materials, wherein the first powder material is pure silicon carbide powder material, the second powder material is uniformly mixed silicon carbide powder material added with 10-30 wt% of active carbon powder, and the third powder material is uniformly mixed silicon carbide powder material added with 1-30 wt% of active carbon powder;

step 2, dividing a powder adding area in the crucible into a first powder adding area 1, a second powder adding area 2 and a third powder adding area 3, setting the height of the crucible powder adding area as h and the radius as r, wherein the height of the second powder adding area is 0.1-0.8 h and the radius as 0.05-0.8r, the height of the third powder adding area is 0.05-0.15h and the radius as r, and the rest space is the first powder adding area;

and 3, adding a certain mass of first powder to the bottom of the crucible, inserting a cylinder which has the same volume as a second powder adding area and does not have an upper bottom and a lower bottom into the center of the crucible, adding the second powder into the cylinder, adding the rest of the first powder into a gap between the cylinder and the crucible, carefully taking out the cylinder, and adding a third powder to complete the addition of the powder with the carbon source in the growth of the silicon carbide crystal by the PVT method.

In the method for adding powder for adding carbon source in the growth of silicon carbide crystal by PVT method in the embodiment, the activated carbon powder in the second powder in the step 1 is high-purity amorphous carbon powder with the particle size of 500 μm and the addition amount of 15 wt%.

In the method for adding powder for adding carbon source in the growth of silicon carbide crystal by PVT method in the embodiment, the activated carbon powder in the third powder in the step 1 is high-purity amorphous carbon powder with the particle size of 800 μm and the addition amount of 10 wt%.

In the method for adding the powder for adding the carbon source in the growth of the silicon carbide crystal by the PVT method in the embodiment, in the step 2, the height of the second powder adding area is 0.6h, the radius is 0.5r, and the height of the third powder adding area is 0.1h, and the radius is r.

In the method for adding the powder for adding the carbon source in the growth of the silicon carbide crystal by the PVT method according to the embodiment, the mass ratio of the first powder, the second powder and the third powder in step 3 is 1875:375: 250.

In the method for adding the carbon source-added powder in the growth of the silicon carbide crystal by the PVT method, the crucible cover is adhered with the seed crystal, then the whole crucible with the carbon source-added powder is put into the crystal growth furnace to start the crystal growth, and the growth condition used in the growth process is 10^-3atm argon atmosphere, growth temperature 2300 deg.C, growth time 80 h.

Compared with the method of adding carbon powder into powder in all areas, the method can improve the total quality of the grown crystal, maintain the capability of improving the carbon-silicon ratio and reducing the generation of defects.

The mass of the crystal grown by the method for adding the powder for adding the carbon source in the growth of the silicon carbide crystal by the PVT method according to the embodiment is shown in Table 1:

TABLE 1 Crystal growth quality

	Detailed description of the invention	Comparative example 1	Comparative example 2
				Mass/g of grown crystal	1199	1015	1321
Microtube Density (pieces/cm)2)	1.0	0.9	3.3
				Dislocation Density (units/cm)2)	7762	7898	9112

Comparative example 1:

10 percent of amorphous carbon powder with the particle size of 500 microns is directly added into the silicon carbide powder and mixed evenly. The mixed powder was directly added to a crucible in an amount of 2500 g. The growth conditions used during the crystal growth process are the same as in the first embodiment.

Comparative example 2:

the crystals were grown using the same conditions as used in the first embodiment using a common silicon carbide powder.

As can be seen from table 1, the first embodiment improves the crystal quality in the growth process while maintaining the ability of the prior method to reduce defect density.

The second embodiment is as follows:

a method for adding powder of an additional carbon source in growth of silicon carbide crystals by a PVT method comprises the following steps:

step 1, respectively preparing three different powder materials, wherein the first powder material is pure silicon carbide powder material, the second powder material is uniformly mixed silicon carbide powder material added with 10-30 wt% of active carbon powder, and the third powder material is uniformly mixed silicon carbide powder material added with 1-30 wt% of active carbon powder;

step 2, dividing a powder adding area in the crucible into a first powder adding area, a second powder adding area and a third powder adding area, setting the height of the crucible powder adding area as h and the radius as r, wherein the height of the second powder adding area is 0.1-0.8 h and the radius as 0.05-0.8r, the height of the third powder adding area is 0.05-0.15h and the radius as r, and the rest space is the first powder adding area;

and 3, adding a certain mass of first powder to the bottom of the crucible, inserting a cylinder which has the same volume as a second powder adding area and does not have an upper bottom and a lower bottom into the center of the crucible, adding the second powder into the cylinder, adding the rest of the first powder into a gap between the cylinder and the crucible, carefully taking out the cylinder, and adding a third powder to complete the addition of the powder with the carbon source in the growth of the silicon carbide crystal by the PVT method.

In the method for adding the powder for adding the carbon source in the growth of the silicon carbide crystal by the PVT method, when the powder is added into the crucible, high-purity carbon powder is added into the areas 2 and 3 formed by sublimation and recrystallization in the corresponding growth process. The gas phase enters the growth cavity in the sequence of 1 region to 2 regions and then to 3 regions in the growth process. In the process, the material exchange reaction of the gas phase and the solid phase flowing through the 2 area and the 3 area is utilized to improve the carbon-silicon ratio in the gas phase, improve and maintain the growth rate of the silicon carbide crystal, and simultaneously reduce the unstable change of a thermal field caused by the change of the thermal conductivity coefficient due to the consumption of the graphite crucible. Compared with the method of adding high-purity carbon powder in all the areas, the method removes the unreasonable addition of the area 1, reserves the reasonable addition of the areas 2 and 3, and improves the growth amount of the silicon carbide crystal compared with the original method.

Compared with the method of adding carbon powder to powder in all areas, the method for adding carbon source powder in the growth of the PVT method silicon carbide crystal can improve the total mass of the grown crystal, maintain the capability of improving the carbon-silicon ratio and reducing the generation of defects.

The third concrete implementation mode:

according to the second specific embodiment, in the step 1, the activated carbon powder in the second powder is high-purity amorphous carbon powder or graphite powder with a particle size of 100-1000 μm.

The fourth concrete implementation mode:

according to the second specific embodiment, in the second powder material of step 1, the activated carbon powder is high-purity amorphous carbon powder with a particle size of 500 μm and an addition amount of 15 wt%.

The fifth concrete implementation mode:

according to the second specific embodiment, in the step 1, the activated carbon powder in the third powder is high-purity amorphous carbon powder or graphite powder with a particle size of 100-1000 μm.

The sixth specific implementation mode:

according to the second specific embodiment, in the step 1, the activated carbon powder in the third powder is high-purity amorphous carbon powder with a particle size of 800 μm and an addition amount of 10 wt%.

The seventh embodiment:

according to the second specific embodiment, in the step 2, the height of the second powder adding area is 0.6h, the radius is 0.5r, and the height of the third powder adding area is 0.1h, and the radius is r.

The specific implementation mode is eight:

according to the method for adding the powder of the additional carbon source in the growth of the silicon carbide crystal by the PVT method described in the second embodiment, the mass ratio of the first powder, the second powder and the third powder in the step 3 is 1875-2000:375-450: 250-350.

The specific implementation method nine:

according to the second specific embodiment, in the step 3, the mass ratio of the first powder, the second powder and the third powder is 1875:375: 250.

The detailed implementation mode is ten:

according to the second embodiment, a seed crystal is adhered to a crucible cover, then the whole crucible with the powder of the additional carbon source is put into a crystal growth furnace to start crystal growth, and the growth conditions used in the growth process are 10^-3atm argon atmosphere, growth temperature 2300 deg.C, growth time 80 h.