阅读说明：本技术 高纯碳化硅源粉制备方法 (Preparation method of high-purity silicon carbide source powder ) 是由 王亚哲 皮孝东 徐所成 姚秋鹏 陈鹏磊 于 2021-09-13 设计创作，主要内容包括：本申请公开了一种高纯碳化硅源粉制备方法,包括：高纯碳粉提纯步骤：在抽真空环境下,将高纯碳粉在石墨坩埚中进行高温煅烧,煅烧完成后,停止加热,通入保护气体进行降温,得到提纯后的碳粉；高纯硅熔融步骤：将高纯硅放置在含有保护气体氛围的石英坩埚内部进行高温熔化,得到熔硅；混合步骤：将提纯后的碳粉加入到熔硅中,控制石英坩埚以设定转速转动设定时间,然后通入保护气体进行降温,得到碳硅固熔体；粉碎步骤：对碳硅固熔体进行碎块,得到高纯碳化硅源粉。本申请能够将碳粉和硅均匀混合并且降低氮的摄入,且本方法中对于加热的温场精度要求不高,加热区域的尺寸可以做得比较大,一次混料的量可以达到相当的规模,非常适用大规模生产。(The application discloses a preparation method of high-purity silicon carbide source powder, which comprises the following steps: and (3) purifying high-purity carbon powder: calcining high-purity carbon powder in a graphite crucible at high temperature in a vacuum environment, stopping heating after the calcination is finished, and introducing protective gas for cooling to obtain purified carbon powder; melting high-purity silicon: placing high-purity silicon in a quartz crucible containing protective gas atmosphere for high-temperature melting to obtain molten silicon; mixing: adding the purified carbon powder into molten silicon, controlling a quartz crucible to rotate at a set rotating speed for a set time, and then introducing protective gas to cool to obtain a carbon-silicon solid solution; a crushing step: and (4) fragmenting the carbon-silicon solid solution to obtain high-purity silicon carbide source powder. According to the method, the carbon powder and the silicon can be uniformly mixed, the nitrogen intake is reduced, the requirement on the precision of a heating temperature field is not high, the size of a heating area can be made larger, the amount of once mixed material can reach a certain scale, and the method is very suitable for large-scale production.)

1. A preparation method of high-purity silicon carbide source powder is characterized by comprising the following steps:

and (3) purifying high-purity carbon powder: calcining high-purity carbon powder in a graphite crucible at high temperature in a vacuum environment, stopping heating after the calcination is finished, and introducing protective gas for cooling to obtain purified carbon powder;

melting high-purity silicon: placing high-purity silicon in a quartz crucible containing protective gas atmosphere for high-temperature melting to obtain molten silicon;

mixing: adding the purified carbon powder into molten silicon, controlling a quartz crucible to rotate at a set rotating speed for a set time, and then introducing protective gas to cool to obtain a carbon-silicon solid solution;

a crushing step: and (4) fragmenting the carbon-silicon solid solution to obtain high-purity silicon carbide source powder.

2. The method for preparing high-purity silicon carbide source powder according to claim 1, wherein the purity of the high-purity carbon powder is more than or equal to 99.999%; the high-purity silicon is a massive silicon material, a granular silicon material or a powdery silicon material, and the purity of the high-purity silicon is more than or equal to 99.999 percent.

3. The method of claim 1 wherein the shielding gas is argon.

4. The method for preparing high purity silicon carbide source powder according to claim 1 wherein in the mixing step, the solid carbon-silicon melt is cooled to room temperature or a predetermined temperature and then removed from the quartz crucible.

5. The method for preparing high purity silicon carbide source powder of claim 1 wherein the step of purifying high purity carbon powder is performed at a temperature of 1 x 10 or less^-3And (3) carrying out high-temperature calcination in a vacuum environment of Pa, wherein the temperature is raised to 1900-2100 ℃ within 5-7 hours and is kept for 1.5-2.5 hours.

6. The method of claim 1 wherein the high purity silicon carbide source powder is melted at a vacuum of 1 x 10 or less^-3Under the condition of Pa, introducing protective gas to ensure that the pressure of the environment where the high-purity silicon is positioned reaches 10-50 mbar; and when the high-temperature melting is carried out, the temperature is heated to the melting point temperature of the silicon until the high-purity silicon is completely melted, and the high-purity silicon is kept in a melted state.

7. The method for preparing high purity silicon carbide source powder as claimed in claim 1, wherein in the mixing step, the quartz crucible is rotated at a speed of 15-50rpm for 30-60 minutes, and then the temperature is lowered by introducing a shielding gas to the crucible, and the temperature is lowered to room temperature or a set temperature.

8. The method of claim 1 wherein the method is performed by a silicon carbide processing tool comprising an upper heating chamber, a sub-chamber, and a lower heating chamber arranged in sequence from top to bottom:

the lower part of the upper heating chamber is provided with a water-cooled upper flange, the water-cooled upper flange is provided with a first exhaust pipe and a first air inlet pipe, the upper heating chamber is internally provided with a graphite crucible, and the side wall of the upper heating chamber is provided with an upper heating element;

the upper part of the lower heating chamber is provided with a water-cooled lower flange, a second air exhaust pipe and a second air inlet pipe are arranged on the water-cooled lower flange, a quartz crucible is arranged in the lower heating chamber, and a lower heating element is arranged on the side wall of the lower heating chamber;

the auxiliary chamber is provided with a lifting mechanism, and the lifting mechanism is used for moving the graphite crucible into the lower heating chamber and pouring high-purity carbon powder into the quartz crucible;

the silicon carbide processing equipment further comprises a rotating device, and the rotating device is used for driving the quartz crucible to rotate.

9. The method of claim 8 wherein the upper and lower heating elements are heating coils.

10. The method of claim 8 wherein the graphite crucible has two coaxially disposed mounting holes on the outer sidewall of the upper end thereof, and a connecting hole on the outer sidewall of the lower end thereof, and wherein the elevating mechanism comprises:

a first lifting element comprising a first rod capable of telescoping, the end of the first rod having a skewed slot;

the middle part of the lifting hook is hung in the chute, rotating shafts are arranged at two ends of the lifting hook, the rotating shafts at two ends of the lifting hook are respectively clamped into two mounting holes of the graphite crucible, and the graphite crucible can rotate around the rotating shafts;

a second lifting element comprising a telescoping second rod;

one end of the stay cable is connected with the second rod, the other end of the stay cable is buckled on the connecting hole of the graphite crucible, and the second lifting element is used for driving the stay cable to move so as to enable the graphite crucible to topple.

Technical Field

The invention relates to the field of silicon carbide preparation, in particular to a preparation method of high-purity silicon carbide source powder.

Background

The SiC (silicon carbide) single crystal is used as a third-generation wide-band-gap semiconductor material, has the properties of wide forbidden band, high thermal conductivity, high electron saturation migration rate, high breakdown electric field and the like, is considered to be an ideal semiconductor material for manufacturing optoelectronic devices, high-frequency high-power devices and high-temperature electronic devices, has wide application in the aspects of white light illumination, optical storage, screen display, aerospace, oil exploration, automation, radar and communication, automobile electronization and the like, and particularly, the semi-insulating silicon carbide is considered to be an optimal substrate of a radio frequency device.

At present, the preparation of semi-insulating silicon carbide generally adopts a PVT (physical vapor transport) method, and the purity (mainly nitrogen content) of SiC powder plays an important role in the crystallization quality and the electrical property of SiC single crystals prepared by the PVT method, particularly high-purity semi-insulating single crystals.

The prior silicon carbide source powder synthesis method inevitably introduces nitrogen in the subsequent source powder synthesis and crystal preparation because a large amount of nitrogen is adsorbed on the surface of carbon powder. In addition, when the silicon carbide source powder is synthesized by the traditional process, the partial region of the synthesized source powder is seriously graphitized due to the uneven mixing of carbon and silicon, and the quality of the source powder is seriously influenced. In the preparation of silicon carbide source powder, how to uniformly mix carbon powder and silicon and reduce the intake of nitrogen is a great technical problem in the preparation of high-purity silicon carbide source powder.

Disclosure of Invention

Aiming at the problems, the invention overcomes at least one defect and provides a preparation method of high-purity silicon carbide source powder.

The technical scheme adopted by the invention is as follows:

a preparation method of high-purity silicon carbide source powder comprises the following steps:

and (3) purifying high-purity carbon powder: calcining high-purity carbon powder in a graphite crucible at high temperature in a vacuum environment, stopping heating after the calcination is finished, and introducing protective gas for cooling to obtain purified carbon powder;

melting high-purity silicon: placing high-purity silicon in a quartz crucible containing protective gas atmosphere for high-temperature melting to obtain molten silicon;

mixing: adding the purified carbon powder into molten silicon, controlling a quartz crucible to rotate at a set rotating speed for a set time, and then introducing protective gas to cool to obtain a carbon-silicon solid solution;

a crushing step: and (4) fragmenting the carbon-silicon solid solution to obtain high-purity silicon carbide source powder.

The main purpose of the high-purity carbon powder purification step is to remove nitrogen and metal impurities in graphite; the silicon is stable in property, a large amount of nitrogen is hardly adsorbed on the surface, the purified carbon powder is added into the silicon melt through a mixing step to obtain a carbon-silicon solid solution, carbon in the carbon-silicon solid solution is basically isolated from air, and the effect of removing nitrogen is achieved.

The method can uniformly mix the carbon powder and the silicon and reduce the intake of nitrogen, the requirement on the precision of a heating temperature field is not high, the size of a heating area can be larger, the amount of the once mixed material can reach a certain scale, and the method is very suitable for pretreatment of the early mixed material during large-scale and batch synthesis of the silicon carbide source powder.

In practical application, in the step of purifying the high-purity carbon powder, a molecular pump can be used for vacuumizing; after calcination, the purified carbon powder can be placed in a high vacuum chamber, for example, a vacuum degree of 1 × 10^-3Pa in the cavity.

In practical application, there is no strict order requirement between the high purity carbon powder purification step and the high purity silicon melting step, and the two steps can be performed in tandem or simultaneously.

In one embodiment of the invention, the purity of the high-purity carbon powder is more than or equal to 99.999 percent; the high-purity silicon is a massive silicon material, a granular silicon material or a powdery silicon material, and the purity of the high-purity silicon is more than or equal to 99.999 percent.

In one embodiment of the present invention, the shielding gas is argon.

In one embodiment of the present invention, in the mixing step, the carbon-silicon solid solution is taken out from the quartz crucible after being cooled to the normal temperature or the set temperature.

In one embodiment of the present invention, the purification step of the high purity carbon powder is less than or equal to 1 × 10^-3And (3) carrying out high-temperature calcination in a vacuum environment of Pa, wherein the temperature is raised to 1900-2100 ℃ within 5-7 hours and is kept for 1.5-2.5 hours.

In one embodiment of the present invention, the melting step of the high purity silicon is performed under a vacuum degree of 1 × 10 or less^-3Under the condition of Pa, introducing protective gas to ensure that the pressure of the environment where the high-purity silicon is positioned reaches 10-50 mbar; and when the high-temperature melting is carried out, the temperature is heated to the melting point temperature of the silicon until the high-purity silicon is completely melted, and the high-purity silicon is kept in a melted state.

The melting point temperature of silicon was 1420 ℃, and in actual use, the silicon was heated to a temperature near the melting point temperature of silicon.

In one embodiment of the present invention, in the mixing step, the quartz crucible is rotated at a speed of 15-50rpm for 30-60 minutes, and then protective gas is introduced to cool the quartz crucible to room temperature or a set temperature.

When in actual use, the temperature can be reduced to be near the room temperature within 8 hours.

In an embodiment of the present invention, the method for preparing high purity silicon carbide source powder is implemented by a silicon carbide processing apparatus, which includes an upper heating chamber, an auxiliary chamber, and a lower heating chamber sequentially arranged from top to bottom:

the lower part of the upper heating chamber is provided with a water-cooled upper flange, the water-cooled upper flange is provided with a first exhaust pipe and a first air inlet pipe, the upper heating chamber is internally provided with a graphite crucible, and the side wall of the upper heating chamber is provided with an upper heating element;

the upper part of the lower heating chamber is provided with a water-cooled lower flange, a second air exhaust pipe and a second air inlet pipe are arranged on the water-cooled lower flange, a quartz crucible is arranged in the lower heating chamber, and a lower heating element is arranged on the side wall of the lower heating chamber;

the auxiliary chamber is provided with a lifting mechanism, and the lifting mechanism is used for moving the graphite crucible into the lower heating chamber and pouring high-purity carbon powder into the quartz crucible;

the silicon carbide processing equipment further comprises a rotating device, and the rotating device is used for driving the quartz crucible to rotate.

In one embodiment of the present invention, the upper heating element and the lower heating element are heating coils.

In one embodiment of the present invention, the outer sidewall of the upper end of the graphite crucible has two coaxially disposed mounting holes, the outer sidewall of the lower end of the graphite crucible has a connection hole, and the lifting mechanism includes:

a first lifting element comprising a first rod capable of telescoping, the end of the first rod having a skewed slot;

the middle part of the lifting hook is hung in the chute, rotating shafts are arranged at two ends of the lifting hook, the rotating shafts at two ends of the lifting hook are respectively clamped into two mounting holes of the graphite crucible, and the graphite crucible can rotate around the rotating shafts;

a second lifting element comprising a telescoping second rod;

one end of the stay cable is connected with the second rod, the other end of the stay cable is buckled on the connecting hole of the graphite crucible, and the second lifting element is used for driving the stay cable to move so as to enable the graphite crucible to topple.

The invention has the beneficial effects that: the main purpose of the high-purity carbon powder purification step is to remove nitrogen and metal impurities in graphite; the silicon is stable in property, a large amount of nitrogen is hardly adsorbed on the surface, the purified carbon powder is added into the silicon melt through a mixing step to obtain a carbon-silicon solid solution, carbon in the carbon-silicon solid solution is basically isolated from air, and the effect of removing nitrogen is achieved.

Description of the drawings:

FIG. 1 is a schematic view of a silicon carbide processing apparatus;

fig. 2 is a schematic view of the elevating mechanism.

The figures are numbered:

1. an upper heating chamber; 2. a sub-chamber; 3. a lower heating chamber; 4. a first exhaust tube; 5. a first intake pipe; 6. a graphite crucible; 7. an upper heating element; 8. water-cooling the upper flange; 9. water-cooling the lower flange; 10. a second extraction tube; 11. a second intake pipe; 12. a lower heating element; 13. a lifting mechanism; 14. a rotating device; 15. a first lifting element; 16. a first lever; 17. a chute; 18. a hook; 19. a second lifting element; 20. a second lever; 21. a pull rope.

The specific implementation mode is as follows:

the present invention will be described in detail below with reference to the accompanying drawings.

A preparation method of high-purity silicon carbide source powder comprises the following steps:

and (3) purifying high-purity carbon powder: calcining high-purity carbon powder in a graphite crucible at high temperature in a vacuum environment, stopping heating after the calcination is finished, and introducing protective gas for cooling to obtain purified carbon powder;

melting high-purity silicon: placing high-purity silicon in a quartz crucible containing protective gas atmosphere for high-temperature melting to obtain molten silicon;

mixing: adding the purified carbon powder into molten silicon, controlling a quartz crucible to rotate at a set rotating speed for a set time, and then introducing protective gas to cool to obtain a carbon-silicon solid solution;

a crushing step: and (4) fragmenting the carbon-silicon solid solution to obtain high-purity silicon carbide source powder.

The main purpose of the high-purity carbon powder purification step is to remove nitrogen and metal impurities in graphite; the silicon is stable in property, a large amount of nitrogen is hardly adsorbed on the surface, the purified carbon powder is added into the silicon melt through a mixing step to obtain a carbon-silicon solid solution, carbon in the carbon-silicon solid solution is basically isolated from air, and the effect of removing nitrogen is achieved.

The method can uniformly mix the carbon powder and the silicon and reduce the intake of nitrogen, the requirement on the precision of a heating temperature field is not high, the size of a heating area can be larger, the amount of the once mixed material can reach a certain scale, and the method is very suitable for pretreatment of the early mixed material during large-scale and batch synthesis of the silicon carbide source powder.

In practical application, in the step of purifying the high-purity carbon powder, a molecular pump can be used for vacuumizing; after calcination, the purified carbon powder can be placed in a high vacuum chamber, for example, a vacuum degree of 1 × 10^-3Pa in the cavity.

In practical application, there is no strict order requirement between the high purity carbon powder purification step and the high purity silicon melting step, and the two steps can be performed in tandem or simultaneously.

In this embodiment, the purity of the high-purity carbon powder is more than or equal to 99.999%; the high-purity silicon is a massive silicon material, a granular silicon material or a powdery silicon material, and the purity of the high-purity silicon is more than or equal to 99.999 percent.

In this embodiment, the shielding gas is argon.

In this embodiment, in the mixing step, the carbon-silicon solid solution is taken out from the quartz crucible after being cooled to the normal temperature or the set temperature.

In this embodiment, the purification step of the high purity carbon powder is less than or equal to 1 × 10^-3And (3) carrying out high-temperature calcination in a vacuum environment of Pa, wherein the temperature is raised to 1900-2100 ℃ within 5-7 hours and is kept for 1.5-2.5 hours.

In this example, the high purity silicon melting step was carried out in a vacuum of 1X 10 or less^-3Under the condition of Pa, introducing protective gas to ensure that the pressure of the environment where the high-purity silicon is positioned reaches 10-50 mbar; and when the high-temperature melting is carried out, the temperature is heated to the melting point temperature of the silicon until the high-purity silicon is completely melted, and the high-purity silicon is kept in a melted state.

The melting point temperature of silicon was 1420 ℃, and in actual use, the silicon was heated to a temperature near the melting point temperature of silicon.

In this embodiment, in the mixing step, the quartz crucible is rotated at a speed of 15-50rpm for 30-60 minutes, and then the protective gas is introduced to cool the quartz crucible to room temperature or a predetermined temperature.

When in actual use, the temperature can be reduced to be near the room temperature within 8 hours.

As shown in fig. 1, in the present embodiment, the method for preparing high purity silicon carbide source powder is implemented by a silicon carbide processing apparatus including an upper heating chamber 1, a sub-chamber 2, and a lower heating chamber 3 arranged in this order from top to bottom:

the lower part of the upper heating chamber 1 is provided with a water-cooled upper flange 8, the water-cooled upper flange 8 is provided with a first exhaust pipe 4 and a first air inlet pipe 5, a graphite crucible 6 is arranged in the upper heating chamber 1, and the side wall of the upper heating chamber 1 is provided with an upper heating element 7;

the upper part of the lower heating chamber 3 is provided with a water-cooled lower flange 9, the water-cooled lower flange 9 is provided with a second air suction pipe 10 and a second air inlet pipe 11, a quartz crucible is arranged in the lower heating chamber 3, and the side wall of the lower heating chamber 3 is provided with a lower heating element 12;

the auxiliary chamber 2 is provided with a lifting mechanism 13, and the lifting mechanism 13 is used for moving the graphite crucible 6 into the lower heating chamber 3 and pouring high-purity carbon powder into the quartz crucible;

the silicon carbide processing equipment further comprises a rotating device 14, and the rotating device 14 is used for driving the quartz crucible to rotate.

As shown in fig. 1, in the present embodiment, the upper heating element 7 and the lower heating element 12 are heating coils.

As shown in fig. 2, in the present embodiment, the graphite crucible 6 has two coaxially disposed mounting holes (not shown) on the outer side wall of the upper end thereof, the graphite crucible 6 has a connecting hole (not shown) on the outer side wall of the lower end thereof, and the lifting mechanism 13 includes:

a first lifting member 15 including a first rod 16 capable of telescoping, an end of the first rod 16 having a diagonal slot 17;

a hook 18, the middle of which is hung in the chute 17, and two ends of which are provided with rotating shafts (not shown in the figure), the rotating shafts at two ends of the hook 18 are used for being respectively clamped into two mounting holes of the graphite crucible 6, and the graphite crucible 6 can rotate around the rotating shafts;

a second lifting element 19 comprising a second rod 20 which is telescopic;

one end of the pulling rope 21 is connected with the second rod 20, the other end of the pulling rope is buckled on the connecting hole of the graphite crucible 6, and the second lifting element 19 is used for driving the pulling rope 21 to move so as to enable the graphite crucible 6 to incline.

The silicon carbide processing equipment of the embodiment is used for implementing a specific step of the method of the embodiment:

step 1: high-purity carbon powder (the purity is more than or equal to 99.999 percent) is filled into the graphite crucible 6 of the upper heating chamber 1. A certain proportion of high-purity silicon (the purity is more than or equal to 99.999 percent) is put into a quartz crucible of the lower heating chamber 3.

Step 2: the upper heating chamber 1 and the lower heating chamber 3 are respectively evacuated and leak-tested by a molecular pump connected with the first air exhaust pipe 4 and the second air exhaust pipe 10, and the vacuum degree is 1 multiplied by 10^-3In the case of Pa, the leak rate within 1 hour cannot exceed 1 Pa.

And step 3: the upper heating element 7 is operated to raise the temperature of the upper heating chamber 1 to 2000 degrees for 6 hours and to maintain it for 2 hours. During which the molecular pump continuously vacuums the upper heating chamber 1. Then stopping heating, introducing high-purity argon through the first air inlet pipe 5, and cooling;

and introducing protective gas argon into the lower heating chamber 3 through a second air inlet pipe 11 to enable the pressure of the lower heating chamber 3 to reach 10-50mbar, then operating a lower heating element 12, raising the temperature of the lower heating chamber 3 to the melting point temperature (about 1420 ℃) of silicon, and keeping the state after the silicon material is completely melted.

And 4, step 4: when the temperature of the upper heating chamber 1 is reduced to be near the room temperature, the water-cooled upper flange 8 is opened, the graphite crucible 6 in the upper heating chamber 1 is taken out and is fixed on the lifting mechanism 13 in the auxiliary chamber 2, and specifically, the rotating shafts at two ends of the lifting hook 18 are respectively clamped into two mounting holes of the graphite crucible 6;

and 5: opening a lower flange of the auxiliary chamber 2, operating a first lifting element 15, moving the graphite crucible 6 filled with purified carbon powder downwards to the position near the molten silicon liquid level through a first rod 16, then operating a second lifting element 19, driving a pull rope 21 to move through a second rod 20, enabling the graphite crucible 6 to be toppled over, pouring the purified carbon powder into the molten silicon, simultaneously starting a rotating device 14, enabling the quartz crucible filled with the carbon powder and the molten silicon to be at a higher rotating speed (15-50rpm), keeping the state for 30-60 minutes, then introducing argon gas to cool, and returning to the position near the room temperature within 8 hours.

Step 6: and taking out the carbon-silicon solid solution for fragmenting to obtain high-purity silicon carbide source powder, wherein the obtained source powder can be used for subsequent powder synthesis.

The above description is only for the preferred embodiment of the present invention and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings can be directly or indirectly applied to other related technical fields and are included in the scope of the present invention.