The liquid phase method is a long-established silicon carbide (SiC) crystal preparation technology, which was widely popular in the 60s of the 20th century, and even surpassed the physical vapor phase transport (PVT) method. However, with the technological breakthrough of PVT method in the 70s, the liquid phase method was gradually marginalized. Today, the PVT method has brought renewed attention to the industry due to the challenges it encounters in manufacturing large-size SiC crystals and reducing costs.
At the heart of the liquid phase method is the use of a graphite crucible as a reactor to increase its solubility to carbon by adding a co-solvent to molten pure silicon. In the hot area of the crucible near the wall, the carbon dissolves in molten silicon; At the lower temperature of the silicon carbide seed crystal at the center of the crucible, the solubility of the carbon decreases, forming a supersaturated solution. At this point, the carbon in solution binds to silicon and undergoes epitaxial growth on the surface of the seed crystal. At the same time, the precipitated carbon in the solution continues to flow back to the crucible wall, where it continues to dissolve and form a cycle.
Despite its potential, the liquid phase method still faces some technical challenges. First, a balance needs to be found between the growth rate and the quality of the crystals, as too fast a growth rate can lead to defects and even crystal cracking. In addition, due to the continuous corrosion of graphite crucibles during the growth process, the stability of the crystal growth environment may be affected. Thirdly, due to the difficulty of testing under high-temperature growth conditions, the thermodynamic parameters (such as freezing point, surface tension, viscosity, etc.) in the liquid phase have not been fully mastered, which are important directions for future research.
Recently, Tianyue Advanced announced the successful preparation of low-defect 8-inch crystals using the liquid phase method, which is an important breakthrough in the field of silicon carbide single crystal growth. Domestic semiconductor companies in the lattice field have also made progress in the liquid phase method, successfully producing 6-inch silicon carbide crystals. Internationally, Japanese research institutions and companies, including Nagoya University, University of Tokyo, Sumitomo, Toyota, Oxide, etc., are also actively investing in the research and development of liquid phase methods, indicating that this technology is gradually moving to the forefront on a global scale.
In terms of crystal growth furnace equipment manufacturers, the domestic liquid phase method is currently relatively mature with Fenggang chemical technology, and has achieved mass production and delivery to many domestic and foreign customers; In addition, equipment manufacturers such as Jingsheng, Huachuang and Hanhong are also actively developing to meet the needs of the domestic market. In the future, with technological breakthroughs, the liquid phase method is very likely to become a new technological breakthrough for 8-inch silicon carbide substrates. Semiconductors