Growth Rate and Surface Morphology of Silicon Nitride Thin Films by Low Pressure Chemical Vapor Deposition

Silicon nitride thin films (SiNx) were prepared on silicon wafers from SiHCl3 (TCS)-NH3-N2 system via low pressure chemical vapor deposition (LPCVD) from 730℃to 830℃ in a hot-wall horizontal tubular reactor. By spectroscopic ellipsometer and Atomic Force Microscope (AFM), the growth rate and surface morphology of the films were investigated with various deposition parameters, including total pressure, substrate temperature and reactive gas feed ratio. As total pressure increases, growth rate increases at lower pressure and then decreases at higher pressure. The dependence of growth rate on substrate temperature is similar to that of total pressure. However, as NH3/TCS ratio increases, growth rate gradually increases and eventually amounts to a constant. The apparent activation energy of the reaction from 730℃ to 830℃ is about 171kJ/mol. AFM results reveal that lower growth rate is favor to improve film uniformity. SiNx films with promising surface roughness can be prepared under appropriate deposition conditions.