Mass spectrometry detection of radicals in SiH₄-CH₄-H₂glow discharge plasmas

Abstract

After reviewing the various in situ and non-intrusive diagnostics of radicals in low-pressure discharges, we present the technique of threshold ionization mass spectrometry. This technique has been applied to measure SiHn, CHn (n<or=3) and H radical densities in radio frequency (RF) capacitively coupled parallel plate discharges of silane, methane and hydrogen. The procedure of determination of absolute radical densities is detailed. The comparison of SiH3 and CH3 densities near the wall reveals large differences in surface reaction probabilities. Then, the contribution of SiHn and CHn (n<or=3) flux to a-Si:H and a-C:H deposition is investigated and compared with the growth rate. Finally, for the first time, we report a measurement of H atom density by mass spectrometry in a hydrogen discharge.