Langmuir probe and optical emission studies in a radio frequency (rf) magnetron plasma used for the deposition of hydrogenated amorphous silicon

The characteristics of a low pressure radio frequency (rf) magnetron argon plasma with varying hydrogen flow rate have been investigated using a Langmuir probe and optical emission spectroscopy. Plasma measurements have been taken for conditions involving a silicon target to complement a previous study on the growth process and the effect of varying hydrogen flow rate on the deposition rate and hydrogen content of amorphous silicon films. This previous study indicated a sudden increase in the deposition rate when hydrogen is introduced into the argon discharge, and was attributed to an assumed increase in ion density (not measured). However, our current Langmuir probe studies show that the ion density decreases with the addition of hydrogen. It is now proposed that the increased deposition rate is due to the presence of hydrogen, which facilitates the uptake of silicon. Langmuir results on the effect of rf power show that the ion density does increase with increasing power which is consistent with the prior work.