A high-quality semiconducting silicon carbide powder and a method of making

Abstract

The application discloses a high-crystalline semiconductor silicon carbide powder and a preparation method thereof. High-purity silicon carbide single crystal is cracked or broken, and silicon carbide powder with a particle size of 10-200 microns is screened out and mixed with high-purity carbon powder. The mixed carbon powder and silicon powder are placed at the bottom of a graphite crucible, and the mixed silicon carbide powder and high-purity carbon powder are placed at the upper part. A graphite cover is installed to seal the graphite crucible, and the graphite crucible is placed in a high-temperature sintering furnace. The furnace chamber is closed and vacuumized. The temperature is raised to 1050-1350 DEG C, and the temperature is kept for 1-15 hours. High-purity argon is introduced into the chamber until the pressure in the chamber reaches 10000-80000 Pa. The temperature is continuously raised to 1750-2000 DEG C, and the temperature is kept for 8-15 hours to synthesize the bottom silicon carbide powder. The temperature is continuously raised to 2000-2500 DEG C, and the pressure in the chamber is reduced to 1000-10000 Pa. High-purity argon is continuously introduced at a flow rate of 5-800 sccm, and the temperature is kept for 30-80 hours. The argon introduction is stopped, and the graphite crucible is cooled to room temperature to obtain the high-crystalline semiconductor silicon carbide powder. The high-crystalline semiconductor silicon carbide powder can be applied to the preparation of the third-generation semiconductor material silicon carbide single crystal material with high performance, low defects and low inclusion density.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials technology, specifically relating to a high-crystallinity semiconductor silicon carbide powder and its preparation method. Background Technology

[0002] As a representative of third-generation semiconductor materials, silicon carbide (SiC) semiconductor materials have entered an era of rapid application development. Power devices made from silicon carbide semiconductor materials have been widely used in new energy vehicles, smart high-voltage power grids, industrial automation, uninterruptible power supplies, white goods, solar and wind power generation, and other fields. They exhibit high efficiency in power conversion and excellent stability. Currently, the mature method for preparing single crystals of silicon carbide semiconductors is the physical vapor transport (PVT) method. In the PVT method, silicon carbide crystals are grown by placing silicon carbide powder in a high-temperature region and a seed crystal in a low-temperature region. The powder sublimates in the high-temperature region and deposits on the seed crystal in the low-temperature region. To obtain high-quality silicon carbide semiconductor performance, high-quality requirements are placed on the silicon carbide powder used. Not only is it necessary to improve the purity of the powder, but also to meet higher requirements for the degree of crystallinity.

[0003] US Patent 9487405B2 discloses a method for manufacturing high-purity SiC powder. This method involves reacting a solid carbon source as a raw material with a silicon source obtained by vaporizing silicon and silicon dioxide to produce high-purity SiC powder. By varying the composition of the vaporized silicon source, the molar ratio of the solid carbon source, and the heating temperature and time, this method allows for easy control of the SiC powder size and crystal phase.

[0004] Chinese patent CN111056554A discloses a high-purity silicon carbide powder, its preparation method, and a reactor. The preparation method includes the following steps: 1) providing silicon raw material and a graphite plate assembly, wherein the graphite plate assembly includes at least one graphite plate; 2) placing the silicon raw material and the graphite plate in a crucible, with the graphite plate assembly positioned above the silicon raw material, and a gap between the graphite plate and the silicon raw material; 3) placing the loaded crucible in a heating furnace for high-temperature solid-state synthesis, thereby obtaining the high-purity silicon carbide powder. This method does not require the addition of additional auxiliary agents to maintain the reaction; and the high temperature and low pressure during the impurity removal stage result in high-purity silicon carbide powder; the silicon carbide product obtained by this method is granular, eliminating the need for crushing / grinding post-processing and preventing the introduction of impurities. However, this method suffers from low efficiency during high-temperature solid-state synthesis, and inclusions may appear in the silicon carbide powder particles, affecting subsequent silicon carbide crystal growth.

[0005] Chinese Patent CN110950341A discloses a silicon carbide powder, its preparation method, and the apparatus used therein. The preparation method of the silicon carbide powder includes the following steps: after removing impurities from carbon powder at 1800~2000℃, silane gas is introduced into the carbon powder in an inert gas environment, and a primary synthesis and a secondary synthesis are performed in a synthesis chamber to obtain silicon carbide powder; wherein, the primary synthesis includes: introducing silane gas into the synthesis chamber at a flow rate of X, at a pressure of 500~800 mbar and a temperature of 1800~2300℃, for a primary synthesis time t1 of 5~25 h; the secondary synthesis includes: introducing silane gas into the synthesis chamber at a flow rate of X+Y*Δt, at a pressure of 500~800 mbar and a temperature of 1800~2300℃, for a secondary synthesis time t2 of 45~125 h; wherein, Y is a positive number, and Δt is 0~t2, increasing continuously with time. Although this method can improve the synthesis purity of silicon carbide powder, the process control is cumbersome and complex, and it is difficult to implement in practice.

[0006] The methods disclosed above only address the purity of synthesized silicon carbide powder, without addressing its crystallinity. In the growth of semiconductor-grade silicon carbide single crystals, besides the purity and size of the powder affecting growth quality, the crystallinity of the powder also influences internal defects. For example, the powder synthesis methods disclosed above rely on spontaneous nucleation within the powder to form particles. During the vigorous reaction, excess carbon or silicon inclusions and multiple nucleation centers are formed and encapsulated during growth. These heterogeneous inclusions or encapsulations can cause disturbances in the dielectric flow during silicon carbide crystal growth, or be drawn into the crystal by the growth component flow, forming polymorphic or large defects. This leads to a deterioration in the quality of the next crystal growth step. Furthermore, the carbon-silicon atomic ratio in the synthesized silicon carbide powder produced by the above methods deviates significantly from 1:1. Due to the uncontrollable self-propagating reaction process, the number of silicon atoms in the synthesized powder particles will be higher than that of carbon atoms, creating numerous carbon vacancies. Controlling the crystallinity of synthesized semiconductor silicon carbide powder remains a pressing problem in this field. To date, no methods for preparing high-crystalline semiconductor silicon carbide powder have been reported. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a high-purity semiconductor silicon carbide powder and its preparation method. The prepared high-purity semiconductor silicon carbide powder can be used to prepare high-performance, low-defect, and low-inclusion-density third-generation semiconductor material silicon carbide single crystal material.

[0008] This invention is achieved through the following technical solution:

[0009] A method for preparing high-crystalline semiconductor silicon carbide powder includes the following steps:

[0010] (1) The high-purity silicon carbide single crystal is cracked or mechanically crushed, and silicon carbide powder with a particle size of 10-200 μm is screened out and mixed with high-purity carbon powder.

[0011] (2) After mixing carbon powder and silicon powder evenly, place them at the bottom of a graphite crucible. Then place the silicon carbide powder and high-purity carbon powder mixed in step (1) on the top of the graphite crucible, cover it with a graphite cap, place the crucible in a high-temperature sintering furnace, seal the furnace cavity, and evacuate.

[0012] (3) Heat the vacuum chamber to 1050~1350℃ and keep it at that temperature for 1~15h. Then, introduce high-purity argon into the chamber to a pressure of 10000-80000 Pa. Continue to heat the chamber to 1750~2000℃ and keep it at that temperature for 8~15h to achieve the synthesis of bottom silicon carbide powder.

[0013] (4) After the bottom silicon carbide powder is synthesized, continue to heat up to 2000-2500℃, while reducing the pressure in the furnace cavity to 1000-10000Pa, and keep the flow rate of high-purity argon gas continuously at 5-800sccm, and keep it at the temperature for 30-80h.

[0014] (5) Stop the argon gas supply and slowly cool to room temperature to prepare high-crystal semiconductor silicon carbide powder.

[0015] Furthermore, in step (1), the diameter of the high-purity silicon carbide single crystal is 2 to 8 inches, and the purity of the high-purity silicon carbide single crystal and the high-purity carbon powder is greater than 99.999%.

[0016] Furthermore, in step (1), the mass ratio of silicon carbide powder to high-purity carbon powder is 3:1; in step (2), the molar ratio of carbon atoms to silicon atoms in carbon powder and silicon powder is 1:1.

[0017] Furthermore, in step (2), the amount of carbon powder and silicon powder mixed accounts for 1 / 2 to 1 / 3 of the volume inside the crucible; the amount of silicon carbide powder and high-purity carbon powder mixed accounts for 1 / 4 to 1 / 3 of the volume inside the crucible.

[0018] Furthermore, the vacuum level after evacuation in step (2) is below 10⁻⁵ Pa.

[0019] Further, in step (3), the vacuum chamber is heated to 1050~1150℃ and kept at that temperature for 1~15h. High-purity argon gas is introduced into the chamber to a pressure of 10000-80000 Pa. The temperature is then raised to 1750~1900℃ and kept at that temperature for 8~15h.

[0020] Furthermore, after the bottom silicon carbide powder is synthesized in step (4), the temperature is further increased to 2250-2450℃, while the pressure inside the furnace is reduced to 1000-10000Pa, and high-purity argon gas is continuously introduced at a flow rate of 5-800 sccm, and the temperature is maintained for 30-80 hours.

[0021] Furthermore, the cooling rate in step (5) is 0.5 to 3 °C / min.

[0022] In this invention, the high-crystallinity semiconductor silicon carbide powder is prepared by the preparation method described above.

[0023] The method for preparing high-crystalline semiconductor silicon carbide powder of this invention can produce high-crystalline semiconductor silicon carbide powder with a density of 3.15-3.19 g / cm³. 3 Its density is close to that of silicon carbide single crystals, which is 3.16-3.21 g / cm³. 3 This indicates that the crystallinity of the powder is very high. The silicon carbide single crystal material grown using the high-crystalline silicon carbide powder prepared according to this invention has no polymorphism, and the densities of inclusions, microtubes, and dislocation defects are significantly reduced. Its dislocation defect density is 5000 / cm². 2 In summary, the method of this invention has successfully prepared high-crystallinity semiconductor silicon carbide powder.

[0024] The beneficial effects achieved by this invention are as follows:

[0025] (1) The preparation method of high crystal quality semiconductor silicon carbide powder of the present invention can significantly improve the crystallinity of semiconductor-grade silicon carbide powder; by introducing high purity silicon carbide single crystal micro powder particles, a nucleation and growth center point is provided for the subsequent formation of silicon carbide powder, so that the sublimated components can quickly intervene in the growth of near single crystal silicon carbide particles, thereby effectively improving the crystallinity of silicon carbide powder, and making the density of synthesized silicon carbide micro powder closer to the density of silicon carbide single crystal;

[0026] (2) The present invention can effectively reduce the formation of carbon vacancy defects in silicon carbide powder; by mixing high-purity carbon powder around silicon carbide single crystal microparticles, the carbon powder does not participate in the reaction when heated at low temperature; at high temperature, the gaseous atmosphere of carbon components can be effectively improved, so that SiC2, Si2C and Si sublimated around silicon carbide single crystal microparticles can more effectively combine with carbon components to form high-crystalline semiconductor-grade silicon carbide powder with a carbon-to-silicon atom ratio close to 1:1.

[0027] (3) This invention can effectively reduce the defect density inside silicon carbide single crystals grown from high-crystalline materials, especially carbon vacancy defects. The silicon-carbon composition in the atmosphere generated during the later decomposition of high-crystalline silicon carbide powder is closer to a 1:1 ratio, allowing the silicon carbide single crystals to grow in a more orderly manner. This reduces the generation of vacancy defects, and the reduced point defect density increases the migration rate of free carriers, thereby increasing the conductivity of the semiconductor silicon carbide single crystal and improving the performance of subsequent silicon carbide-based power devices. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall assembly of high-crystalline semiconductor-grade silicon carbide powder, where 1 is the graphite crucible cover, 2 is the graphite crucible body, 3b is the mixed powder of carbon powder and silicon powder, 4 is the induction heating coil, and 5 is the mixed powder of silicon carbide powder and high-purity carbon powder.

[0029] Figure 2 Microscopic photograph of the high-crystalline semiconductor silicon carbide powder prepared in Example 1;

[0030] Figure 3 Kikuchi line pattern of electron backscatter diffraction (EBSD) of the high-crystalline semiconductor silicon carbide powder prepared in Example 1;

[0031] Figure 4 A photograph showing the distribution of one-dimensional dislocation defects in silicon carbide single crystals grown from the high-crystalline semiconductor silicon carbide powder prepared in Example 2.

[0032] Figure 5 The diagram shows the overall assembly of silicon carbide powder prepared in Comparative Example 1, where 1 is the graphite crucible cover, 2 is the graphite crucible body, 3a is the mixed powder of carbon powder and silicon powder, and 4 is the induction heating coil.

[0033] Figure 6 Kikuchi line plot of electron backscatter diffraction (EBSD) of silicon carbide powder prepared for Comparative Example 1. Detailed Implementation

[0034] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0035] High crystallinity: refers to solid materials in which the atoms or ions inside are arranged in a highly regular, periodic repeating pattern in three-dimensional space;

[0036] Argon: purity above 99.999%;

[0037] High-purity silicon carbide: refers to silicon carbide single crystal materials with a purity of 99.999% or higher.

[0038] High-purity carbon and silicon powder: refers to carbon and silicon powder with a purity of 99.999% or higher.

[0039] Crystal form: A crystal structure in which molecules or atoms with the same chemical structure are arranged in an orderly manner.

[0040] Example 1

[0041] (1) Clean the 2-8 inch high-purity silicon carbide single crystal (ultrapure water), heat and decompose it, sieve out silicon carbide powder with a particle size of 10-50 μm, and then mix it with high-purity carbon powder. The mass ratio of silicon carbide powder to high-purity carbon powder is 3:1. Mix it evenly in a mixer, take it out and vacuum seal it for later use.

[0042] (2) such as Figure 1 (Schematic diagram of the overall assembly of high-crystalline semiconductor-grade silicon carbide powder) As shown, carbon powder and silicon powder are mixed evenly in a molar ratio of carbon atoms to silicon atoms of 1:1 and placed at the bottom of a graphite crucible, with the filling volume occupying 2 / 3 of the crucible volume. Then, the silicon carbide powder and high-purity carbon powder mixed in step (1) are placed at the top of the graphite crucible, with the filling volume occupying 1 / 4 of the crucible volume. A graphite cap is then added to seal the crucible. The crucible is placed in a high-temperature sintering furnace, the furnace cavity is sealed, and a vacuum is drawn until the vacuum degree reaches 10. - 6 Pa;

[0043] (3) Heat the vacuum chamber to 1050℃ and keep it at that temperature for 10 hours. Remove the moisture and impurities adsorbed on the furnace wall and crucible wall. Introduce high-purity argon gas at a flow rate of 200 sccm to the chamber to a pressure of 80000 Pa. Continue to heat the chamber to 1850℃ and keep it at that temperature for 8 hours to achieve the synthesis of bottom silicon carbide powder.

[0044] (4) After the bottom silicon carbide powder is synthesized, the temperature is raised to 2200℃, while the pressure inside the cavity is reduced to 5000Pa, and the flow rate of high-purity argon gas is continuously introduced at 100sccm, and the temperature is maintained for 50h.

[0045] (5) Stop the argon gas supply, slowly cool to room temperature at 2.5℃ / min, take out the synthesized high-crystal silicon carbide powder, sieve off the excess carbon powder, and obtain high-crystal semiconductor silicon carbide powder.

[0046] Microscopic images of the high-crystalline semiconductor silicon carbide powder prepared in Example 1 are shown below. Figure 2 As shown, its density was tested to be 3.19 g / cm³. 3 The Kikuchi lines of its electron backscatter diffraction (EBSD) were tested. Figure 3As shown, the Kikuchi lines in its diffraction pattern are clear and bright, proving the high crystallinity of the synthesized powder. The silicon carbide single crystals grown using this method are free of polymorphic defects and carbon inclusions, with a dislocation defect density of 3200 / cm². 2 .

[0047] Example 2

[0048] Unlike Example 1, in step (3) of Example 2, the temperature was further increased to 1950°C. The remaining steps and conditions were the same as in Example 1, and the density of the prepared high-crystalline semiconductor silicon carbide powder was 3.20 g / cm³. 3 The image shows the distribution of one-dimensional dislocation defects in silicon carbide single crystals grown from the prepared high-crystalline semiconductor silicon carbide powder. Figure 4 As shown, its dislocation density is low, proving that the synthesized high crystallinity is beneficial to improving the crystallization quality of silicon carbide single crystals.

[0049] Example 3

[0050] Unlike Example 1, in Step (3) of Example 3, the second heat treatment time is 5 hours, while the remaining steps and conditions are the same as in Example 1. The density of the prepared high-crystalline semiconductor silicon carbide powder is 3.18 g / cm³. 3 .

[0051] Example 4

[0052] Unlike Example 1, in step (4) of Example 4, the pressure inside the crucible cavity was reduced to 1000 Pa. The remaining steps and conditions were the same as in Example 1, and the density of the prepared high-crystalline semiconductor silicon carbide powder was 3.17 g / cm³. 3 .

[0053] Example 5

[0054] Unlike Example 1, in step (4) of Example 5, the temperature was raised to 2350℃, while the remaining steps and conditions were the same as in Example 1. The density of the prepared high-crystalline semiconductor silicon carbide powder was 3.18 g / cm³. 3 .

[0055] Example 6

[0056] Unlike Example 1, the heat preservation time in step (4) of Example 6 is 75 hours, while the remaining steps and conditions are the same as in Example 1. The density of the prepared high-crystalline semiconductor silicon carbide powder is 3.20 g / cm³. 3 .

[0057] Comparative Example 1

[0058] Unlike Example 1, the overall assembly diagram of the silicon carbide powder prepared in Comparative Example 1 is as follows: Figure 5As shown, the silicon carbide powder and high-purity carbon powder mixed in step (1) of Example 1 were not added. Only a mixture of silicon powder and carbon powder (molar ratio of carbon atoms to silicon atoms of 1:1) was added to the crucible. The remaining steps and conditions were the same as in Example 1.

[0059] Kikuchi lines of electron backscatter diffraction (EBSD) of silicon carbide powder prepared in Comparative Example 1 are shown below. Figure 6 As shown, the Kikuchi lines in its diffraction pattern are generally blurred, proving that the powder lattice is not complete; the density of the silicon carbide powder is 3.05 g / cm³. 3 .

[0060] Comparative Example 2

[0061] Unlike Example 2, step (4) was omitted in Comparative Example 2. The remaining steps and conditions were the same as in Example 2, and the density of the prepared silicon carbide powder was 3.00 g / cm³. 3 .

Claims

1. A method for preparing high-crystallinity semiconductor silicon carbide powder, characterized in that, Includes the following steps: (1) The high-purity silicon carbide single crystal is cracked or mechanically crushed, and silicon carbide powder with a particle size of 10-200 μm is screened out and mixed with high-purity carbon powder. (2) After mixing carbon powder and silicon powder evenly, place them at the bottom of a graphite crucible. Then place the silicon carbide powder and high-purity carbon powder mixed in step (1) on the top of the graphite crucible, cover it with a graphite cap, place the crucible in a high-temperature sintering furnace, seal the furnace cavity, and evacuate. (3) Heat the vacuum chamber to 1050~1350℃ and keep it at that temperature for 1~15h. Then, introduce high-purity argon into the chamber to a pressure of 10000-80000 Pa. Continue to heat the chamber to 1750~2000℃ and keep it at that temperature for 8~15h to achieve the synthesis of bottom silicon carbide powder. (4) After the bottom silicon carbide powder is synthesized, the temperature is raised to 2000-2500℃, while the pressure in the furnace cavity is reduced to 1000-10000Pa, and the flow rate of high-purity argon gas is continuously introduced at 5-800sccm. The temperature is maintained for 30-80h so that the silicon carbide powder synthesized in step (3) can be sublimated and grow with the silicon carbide powder in step (1) as the nucleation and growth center. (5) Stop the argon gas supply and slowly cool to room temperature to prepare high-crystal semiconductor silicon carbide powder.

2. The method for preparing high-crystallinity semiconductor silicon carbide powder according to claim 1, characterized in that, In step (1), the diameter of the high-purity silicon carbide single crystal is 2 to 8 inches, and the purity of the high-purity silicon carbide single crystal and the high-purity carbon powder is greater than 99.999%.

3. The method for preparing high-crystallinity semiconductor silicon carbide powder according to claim 1, characterized in that, In step (1), the mass ratio of silicon carbide powder to high-purity carbon powder is 3:1; in step (2), the molar ratio of carbon atoms to silicon atoms in carbon powder and silicon powder is 1:

1.

4. The method for preparing high-crystallinity semiconductor silicon carbide powder according to claim 1, characterized in that, In step (2), the amount of carbon powder and silicon powder mixed accounts for 1 / 2 to 1 / 3 of the volume inside the crucible; the amount of silicon carbide powder and high-purity carbon powder mixed accounts for 1 / 4 to 1 / 3 of the volume inside the crucible.

5. The method for preparing high-crystallinity semiconductor silicon carbide powder according to claim 1, characterized in that, Step (2) The vacuum level after evacuation is below 10⁻⁵ Pa.

6. The method for preparing high-crystallinity semiconductor silicon carbide powder according to claim 1, characterized in that, In step (3), the vacuum chamber is heated to 1050~1150℃ and held for 1~15h. High-purity argon gas is introduced into the chamber to a pressure of 10000-80000 Pa. The temperature is then raised to 1750~1900℃ and held for 8~15h.

7. The method for preparing high-crystallinity semiconductor silicon carbide powder according to claim 1, characterized in that, After the bottom silicon carbide powder is synthesized in step (4), the temperature is raised to 2250-2450℃, while the pressure inside the furnace is reduced to 1000-10000Pa, and the flow rate of high-purity argon gas is continuously introduced at 5-800sccm, and the temperature is maintained for 30-80h.

8. The method for preparing high-crystalline semiconductor silicon carbide powder according to claim 1, characterized in that, The cooling rate in step (5) is 0.5 to 3 °C / min.

9. The high-crystallinity semiconductor silicon carbide powder prepared by the preparation method according to any one of claims 1 to 8.

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