Effect of Dilution Gases on the SiH 3 Radical Density in an RF SiH 4 Plasma

Infrared diode laser absorption spectroscopy was used to measure the density of silyl ( SiH 3 ) radicals in low-pressure (4.0 Pa) 13.56-MHz rf plasmas utilizing H 2 /, He/, Ar/, and Xe/SiH 4 gas mixtures. The SiH 3 production frequency per SiH 4 molecule was also derived from the SiH 3 density and its decay rate in the afterglow. The observed SiH 3 density decreased with increasing dilution ratio in all the gas mixtures, but the SiH 3 production frequency per SiH 4 molecule increased significantly for Xe dilution and remained nearly constant for H 2 , He, and Ar dilution. Based on these results, the relative importance of different SiH 3 production channels is discussed.