Effect of Dilution Gases on the SiH3Radical Density in an RF SiH4Plasma

Infrared diode laser absorption spectroscopy was used to measure the density of silyl ( SiH3) radicals in low-pressure (4.0 Pa) 13.56-MHz rf plasmas utilizing H2/, He/, Ar/, and Xe/SiH4gas mixtures. The SiH3production frequency per SiH4molecule was also derived from the SiH3density and its decay rate in the afterglow. The observed SiH3density decreased with increasing dilution ratio in all the gas mixtures, but the SiH3production frequency per SiH4molecule increased significantly for Xe dilution and remained nearly constant for H2, He, and Ar dilution. Based on these results, the relative importance of different SiH3production channels is discussed.