Reduction of harmful effect due to by-product in CVD reactor for 4H-SiC epitaxy

摘要

Harmful effect of by-product on the growth of homo-epitaxial 4H-SiC films using a high speed wafer rotation vertical CVD method was suppressed. Influence of by-product, such as 3C-SiC deposit formed on a hot-wall and Si deposit formed on gas nozzles, on epitaxial growth was investigated in two comparative studies. The analysis of triangular defects with 3C-SiC down-falls on the films revealed that the most of the down-falls which were peeled from the hot-wall adhered to the wafers before the epitaxial growth. By increasing the wafer rotation speed to 300 rpm in the heat-up step before epitaxial growth, the down-falls dropped towards the wafer surface were effectively eliminated, and the maintenance period of the reactor could be increased more than 4 times compared with wafer rotation speed of 50 rpm during the heat-up step. Additionally, the relationship between Si deposit formed on the gas nozzles in the gas inlet and fluctuation of thickness and doping concentration of the films suggested that Si deposit formed on the gas nozzles acts as a trap site of Si source gas. By suppression of the Si deposit using optimizing gas flow condition, no significant fluctuation of thickness and doping concentration of the films were observed and the maintenance period of the gas nozzles could be increased more than 3 times compared with the epitaxial growth using the nozzles on which Si deposit was formed.