Control of growth process for obtaining high-quality a-SiO:H

摘要

Film-growth process of hydrogenated amorphous silicon-oxygen alloys (a-SiO:H) from CO_2/(CO_2 + SiH_4) plasma has been investigated to control the optoelectronic properties in the resulting materials. Optical emission spectroscopy results and simple simulation results for steady-state density of chemical species in the plasma indicate that main film-growth precursors for a-SiO:H are SiH_3, OH, and O. Si dangling-bond defect density is drastically increased in a-SiO:H when increasing the CO_2 gas ratio in CO_2/(CO_2 + SiH_4) plasma, being caused by the increase in the contribution ratio of Si-related short-lifetime species (SiH_x, x < 2) to film growth owing to a severe SiH_4-molecule depletion because of high-rate consumption reaction of SiH_4 with O produced from CO_2 in the plasma. Considering the primary electron impact dissociation reactions of source gas molecules and several secondary chemical reactions in the plasma, the guiding principle for obtaining high quality a-SiO:H has been proposed.