A Plasma Chemistry and Surface Model for the Deposition of a–Si:H from RF Glow Discharges: A Study of Hydrogen Content

An integrated electron kinetics, plasma chemistry, and surface deposition model has been developed to study the relationship between film characteristics and plasma parameters in the plasma enhanced chemical vapor deposition (PECVD) of amorphous hydrogenated silicon (a–Si:H) in low pressure parallel plate RF discharges.The integrated model consists of a Monte-Carlo simulation for the electron distribution function in the RF discharge, a time and spatially dependent plasma chemistry model, and a model for the surface deposition process.The surface model consists of an accounting of the surface density of adsorbed species, and the fractional distribution of various types of bonds (e.g.Si–Si, Si–H, Si–.) in the film.The calculated distribution of radicals in silane discharges will first be discussed.The computed hydrogen content and deposition rates of a-Si:H films from silane and disilane discharges are next discussed and compared to experiment.The dependence of hydrogen content on Rf power and substrate temperature is calculated and agrees well with experiment.Mechanisms are proposed to explain these dependencies.