A Movable Mass Spectroscopy Sampling Apparatus for Measuring Spatial Distribution of Neutral Radicals in Silane Plasma

A movable mass spectroscopy gas sampling apparatus has been established and a straight-line fit of silane depletion fraction f is proposed. The spatial density distributions of SiHn (n = 0?3) radicals in silane radio frequency glow discharge have been measured by a mass spectrometer. The experimental results demonstrate that the densities of the neutral radicals have the peak value near the middle position of electrodes, and the densities of SiH2 and SiH3 are higher than those of Si and SiH in silane plasma. This reveals that SiH2 and SiH3 may be the primary precursors in forming the a-Si:H film.