The application of silicon carbide powder in the production of silicon wafers
The production of silicon wafers is to prepare silicon carbide base first. At present, it is mostly used to improve the Lly method, high -temperature CVD method, and solution method.
Lly method, also known as sublimation method, its basic principle is: in the hollow cylindrical graphite (outer layer of graphite, built -in porous graphite ring), the silicon carbide powder with industrial -grade purity is invested and porous graphite ring Heating between 2500 ° C is decomposed and sublimated at this temperature at this temperature, producing a series of gas phase substances such as silicon single crystal, SI2C and SIC2. Due to the temperature gradient between the inner wall and the porous graphite ring, these gas phases randomly generate crystal nucleus in the inner wall of the polychora. However, Lly’s property rate is low, the crystal nucleus is difficult to control, and different structures will be formed, and the size is limited.
With the deepening of the research, the researchers proposed to improve the Lely method, also known as the physical gas transmission (PVT) method, which is improved on the basis of the Lly method. SIC source to the material transport of seed crystals can control the crystal nucleus and crystals. This method can obtain SIC crystals with larger diameter and lower expansion deficiency density. With the continuous improvement of growth technology, companies that have been industrialized have been industrialized include American Cree, Dowcorning, Ⅱ-ⅵ, Germany’s SiCRYSTAL, Japan’s Nipponsteel, Shandong Tianyue, Tiando Henda in China.
In the PVT method, there are many factors affecting SIC crystal synthesis. Among them, SIC powder as a synthetic raw material will directly affect the growth quality and electrical properties of SIC single crystals. Therefore, in recent years, the preparation of high -purity SIC powder has gradually become a research hotspot in the field of SIC single crystal growth. At present, there are three main methods of synthetic SIC powder in the industry: the first is the solid phase method, and the most representative of the solid phase is the Acheson method and the self -spread high temperature synthesis method; The most representative of the law is the solution-gel method and polymer thermal decomposition method; the third is the gas phase method. The most representative of the gas phase method is the chemical gas deposition method and plasma method.