The influence of the H₂/Ar ratio on surface morphology and structural defects in homoepitaxial 4H-SiC films grown with methyltrichlorosilane

Characterization of surface morphology and crystal defects is reported for homoepitaxial 4H-SiC films grown at high rates (35–40 μm/h) using methyltrichlorosilane (CH₃SiCl₃), as single precursor. The ratio of hydrogen to argon (H₂/Ar) in the carrier gas was varied to determine the effect of hydrogen on the surface morphology and the crystalline defects. Due to hydrogen’s reaction with the graphite heater, adjusting the H₂/Ar ratio effectively changed the C/Si ratio in the gas phase; thereby, influencing surface roughness and dislocation density. Low H₂/Ar ratios of 0.1 and 0.125 produced smooth surfaces without step bunching. Higher H₂/Ar ratios of 0.2 and 0.33 enhanced the conversion of basal plane dislocations into threading edge dislocations and reduced the density of basal plane dislocations to approximately 600 cm^-2. However, at these H₂/Ar ratios, macrosteps formed on the surface and the roughness increased. Micropipes from substrate dissociated into closed-core threading screw dislocations in the films grown with H₂/Ar ratio in the range of 0.1–0.2. At H₂/Ar ratio of 0.33, micropipes propagated into the film, generating hollow-core threading screw dislocations.