How to produce high purity silicon carbide sic powder for growing SiC crystals?

01
Hebei Tongguang Semiconductor Co., Ltd
At present, the commonly used technology for synthesizing high-purity silicon carbide powder mainly adopts high-temperature solid-state synthesis of high-purity silicon powder and high-purity carbon powder, namely self-propagating high-temperature synthesis. To solve the problem of high nitrogen impurity concentration in traditional self-propagating synthesis of SiC powder, Hebei Tongguang Semiconductor Co., Ltd. has invented a low nitrogen impurity concentration silicon carbide powder synthesis method that can be used for the growth of high-purity semi insulating SiC single crystals. This method uses nitrogen removal substances that undergo chemical reactions with nitrogen elements at high temperatures. The formed nitrides exist in a stable form within the temperature range of silicon carbide synthesis, effectively avoiding nitrogen impurities from entering the silicon carbide lattice. It breaks through the current traditional synthesis method of silicon carbide raw materials and achieves the synthesis of low nitrogen content silicon carbide raw materials, with a nitrogen content below 2 × 1016 pieces/cm3, which is particularly suitable for the growth of high-purity semi insulating SiC single crystals.

At present, the most effective method for growing SiC crystals is the Physical Vapor Transport (PVT) method, and the crystals formed in sublimation systems have lower defect levels, making them the main commercial mass production technology. When using PVT method to grow SiC crystals, the growth equipment, graphite components, and insulation materials cannot avoid being contaminated by nitrogen impurities. These materials will adsorb a large amount of nitrogen impurities, resulting in a high content of nitrogen impurities in the SiC crystals grown.
At present, the purity of high-purity SiC powder raw materials produced commercially can generally only reach 99.999%, with a nitrogen content of mostly 5% × A level of over 1016 units/cm3 seriously affects the nitrogen content in its subsequent product - high-purity semi insulating silicon carbide single crystals. Therefore, reducing the nitrogen impurity content in powder raw materials is of great significance for the preparation of high-purity semi insulating silicon carbide crystals. Below, based on the patent information of several well-known enterprises disclosed by Tianyancha, relevant technologies for the preparation of high-purity silicon carbide powder are introduced.

This method includes the following steps:
(1) Mix the silicon raw material and carbon raw material thoroughly;
(2) Add nitrogen removal substances to the mixture of silicon raw materials and carbon raw materials, and then place the crucible containing nitrogen removal substances and carbon silicon mixture raw materials in the reaction chamber; The crucible material is high-purity graphite, with a purity of over 99.9995%;
(3) Vacuum the reaction chamber to reduce the content of oxygen and nitrogen in the reaction chamber;
(4) Heat the reaction chamber, raise the temperature, and cause the nitrogen removal substance to react with the nitrogen element, forming a solid or gas form of nitride that will not decompose below 2400 ℃;
(5) Inject inert gas into the reaction chamber, maintain the pressure of the reaction chamber, gradually increase the temperature of the reaction chamber, cause the carbon raw material and silicon raw material to react, gradually cool to room temperature, and end the reaction;
(6) Remove the nitride from the obtained silicon carbide to obtain low nitrogen content silicon carbide raw material.

02
Beijing Tankblue Semiconductor Co., Ltd
Tianke Heda has invented a preparation method for low nitrogen content silicon carbide powder and silicon carbide single crystal. The preparation method includes the following steps: mixing high-purity silicon powder, high-purity graphite powder, and volatile high-purity organic matter, and letting the volatile high-purity organic matter evaporate to less than 10% of the initial mass under an inert atmosphere. The mixed material is sintered to obtain low nitrogen content silicon carbide powder. The invention uses volatile and high-purity organic compounds to remove nitrogen from the surface of raw materials and grain boundaries during the preparation of silicon carbide powder, thereby reducing the nitrogen content in the product. The experimental results show that the nitrogen content of silicon carbide powder and single crystal is less than 5 × 1016 pieces/cm3.

03
Zhongdian Compound Semiconductor Co., Ltd
Zhongdian Compound Semiconductor Co., Ltd. has invented a synthesis method for silicon carbide powder, which includes: mixing high-purity carbon powder and high-purity silicon powder, and loading them into a graphite crucible. The graphite crucible is lined with fluorinated graphite, and the graphite crucible is placed in the furnace cavity; Raise the temperature of the furnace chamber, and during the heating process, a mixture of hydrogen and inert gas is introduced into the furnace chamber, and the fluorinated graphite lining decomposes to release fluorinated gas; Extract the gas from the furnace chamber, causing the high-purity carbon powder to react with the high-purity silicon powder to obtain intermediate products; Raise the temperature of the furnace chamber to cause the intermediate phase products to react and generate silicon carbide powder. By providing a method for synthesizing silicon carbide powder, high-purity silicon carbide powder can be obtained.

04
Shandong  SICC Advanced Technology Co., Ltd
Tianyue Advanced has invented a device and method for preparing silicon carbide powder, which includes: a furnace body, with a partition board installed inside the furnace body. When the partition board is closed, the part inside the furnace body is divided into two parts; When the partition is opened, the furnace body is internally connected; The surface of the electrode is at least partially covered with carbon source raw materials; Crucible, placed inside the furnace body; The crucible and electrode undergo relative displacement to allow the electrode to enter or leave the crucible. During the melting process of silicon source raw materials, a partition is used to separate the silicon source raw materials and carbonization raw materials in the furnace, avoiding the evaporation of silicon liquid during heating and crystallization at the carbonization raw materials, which affects the growth of powder and improves the quality of powder growth. This method can prevent the evaporation of silicon liquid during the melting process of silicon source raw materials and crystallization at the carbonized raw materials by controlling the opening or closing of the partition, resulting in low nitrogen impurity content and other impurity content in the obtained powder. It can be used for the preparation of high-purity silicon carbide crystals.