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

Abstract

Film-growth process of hydrogenated amorphous silicon–oxygen alloys (a-SiO:H) from CO2/(CO2 + SiH4) 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 SiH3, OH, and O. Si dangling-bond defect density is drastically increased in a-SiO:H when increasing the CO2 gas ratio in CO2/(CO2 + SiH4) plasma, being caused by the increase in the contribution ratio of Si-related short-lifetime species (SiHx, x < 2) to film growth owing to a severe SiH4-molecule depletion because of high-rate consumption reaction of SiH4 with O produced from CO2 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.