Corrosion of SiC-coated graphite susceptor by NH3 and Cl2

This study aims to investigate the corrosion of a SiC-coated graphite susceptor using NH3 and Cl2 in an epitaxial growth environment. The corrosion performance of NH3 with graphite and SiC-coated graphite was investigated through microstructure characterization and mass loss rate changes in detail. Gaseous NH3 had a high corrosion rate on the graphite substrate, but hardly reacted with the SiC coating. Additionally, analyses of the tested samples revealed that Cl2 gas corroded the SiC coating at high temperatures and formed many corrosion holes and residual free carbon on the surface. As the Cl2 concentration increased, the corrosion depth gradually increased. Further experiments on commercial SiC-coated graphite susceptors showed that Cl2 preferentially corroded the grain boundaries of the SiC coating, and then the grains were corroded, resulting in a decrease in the coating strength until cracking and failure.