DETECTION OF H-ATOMS IN RF-DISCHARGE SIH4, CH4 AND H-2 PLASMAS BY 2-PHOTON ABSORPTION LASER-INDUCED FLUORESCENCE SPECTROSCOPY

Hydrogen atoms were detected quantitatively by a two-photon absorption laser-induced fluorescence technique in capacitively coupled and inductively coupled RF-discharge plasmas. In a parallel-plate RF-discharge reactor the density of H atoms measured in a SiH4 plasma diluted with Ar was higher than that diluted with H-2. A comparison of the densities in SiH4, CH4 and H-2 plasmas measured by changing dilution ratio with Ar also showed that H-2 molecules were not easily decomposed and H atoms were mostly produced from decomposition of source SiH4 and CH4 molecules at low RF-power level. Spatial distribution of H atoms effused from an inductively coupled RF-discharge radical source was also measured. Its axial and radial profiles showed the expansion of H atoms towards the chamber wall by diffusion and gas flow. The absolute calibration of H atom density was carried out by a comparison with absorption of Ly(alpha) line line at 121.6 nm.