EFFECT OF HYDROGEN DILUTION ON THE DEPOSITION RATE OF HYDROGENERATED AMORPHOUS-SILICON FILMS IN A MODIFIED PULSED PLASMA DISCHARGE

Hydrogen dilution effects on the growth of a-Si:H films in a modified pulsed plasma discharge are studied for two different silane flow cond itions with hydrogen dilution ranging from 0% to 80%. The increase of deposition rate (r(d)) due to hydrogen dilution is attributed mainly t o changes in electron density (n(e)) and electron decay time constant (tau(e)). Concurrently, it appears that hydrogen dilution mitigates th e deleterious effects of secondary plasma reactions. Increasing the dw ell time of the high power period under hydrogen dilution also increas es r(d), accompanied by an enhancement of photoconductivity ((sigma(ph )) as compared to films grown under similar conditions without dilutio n. The decrease in r(d) at dilution >25% is seen as the onset of a pro cess of etching, presumably by atomic hydrogen, and this limits r(d) i rrespective of the availability of the number of silane molecules at s uch dilutions. Time-resolved optical emission spectroscopy results for H emission supports the above views. (C) 1996 American Institute of Physics.