Film formation mechanisms in the plasma deposition of hydrogenated amorphous silicon

By studying the step coverage of plasma-deposited amorphous silicon and germanium on patterned substrates, we find that the film formation process under device-quality deposition conditions has a substantial component that behaves like a surface rate-limited chemical vapor deposition process, while conditions producing defective material are associated with a much more physical-vapor-deposition-like process. An explanation involving surface reactions of SiHx radicals is proposed.