Synthesis and deposition of silicon nitride films by laser reactive ablation of silicon in low pressure ammonia: A parametric study

The UV laser (lambda=308 nm) ablation of silicon wafers in 1 mbar ambient ammonia results in the deposition of pure and uniform film of amorphous silicon nitride. At low pressures of NH3 (of several to several tens of mu bar), the deposited films are a mixture of amorphous silicon nitride, amorphous nonstoichiometric silicon nitride, and amorphous silicon. The contamination with oxygen is low and is more evident at lower pressures. At ammonia pressures 0.1-1 mbar, the films also contain a certain fraction of hydrogen. Droplets of polycrystalline Si cover the surfaces of some films. This phenomenon is more important at smaller target-collector distances and lower pressures of ambient NH3. (C) 1996 American Vacuum Society.