Sejak penemuannya, silikon karbida telah menarik perhatian luas. Silikon karbida terdiri dari setengah atom Si dan setengah atom C, yang dihubungkan melalui ikatan kovalen melalui pasangan elektron yang berbagi orbital hibrid sp3. In the basic structural unit of its single crystal, four Si atoms are arranged in a regular tetrahedral structure, and the C atom is located at the center of the regular tetrahedron. Conversely, the Si atom can also be regarded as the center of the tetrahedron, thereby forming SiC4 or CSi4. Tetrahedral structure. The covalent bond in SiC is highly ionic, and the silicon-carbon bond energy is very high, about 4.47eV. Due to the low stacking fault energy, silicon carbide crystals easily form various polytypes during the growth process. There are more than 200 known polytypes, which can be divided into three major categories: cubic, hexagonal and trigonal.
At present, the main growth methods of SiC crystals include Physical Vapor Transport Method (PVT method), High Temperature Chemical Vapor Deposition (HTCVD method), Liquid Phase Method, etc. Among them, the PVT method is more mature and more suitable for industrial mass production.
The so-called PVT method refers to placing SiC seed crystals on the top of the crucible, and placing SiC powder as raw material at the bottom of the crucible. In a closed environment of high temperature and low pressure, the SiC powder sublimates and moves upward under the action of temperature gradient and concentration difference. A method of transporting it to the vicinity of the seed crystal and then recrystallizing it after reaching a supersaturated state. This method can achieve controllable growth of SiC crystal size and specific crystal forms.
Waktu posting: 16 April-2024