Laser diagnostics of a silane plasma—SiH radicals in an a-Si:H chemical vapor deposition system

Abstract

Using a laser-induced fluorescence technique, SiH radicals were detected in the rf glow discharge of SiH4 gas during CVD of amorphous silicon. The pressure, flow rate, and rf power dependencies of the relative concentration of SiH radicals were obtained. The spatial distribution of SiH radicals between rf and ground electrodes was also revealed. It was found that the behaviors of the concentration of SiH in the ground electronic state are different from those of SiH in the excited state. The latter was obtained from measurement of the spontaneous emission in the discharge. The rotational temperature of SiH radicals was derived from the laser excitation spectra with computer simulations. The obtained temperature reflects the translational temperature of the parent molecules (SiH4). The rotational energies of SiH radicals in the discharge are thermalized with surroundings by collisions during their lifetimes.