Absolute density of precursor SiH3 radicals and H atoms in H2-diluted SiH4 gas plasma for deposition of microcrystalline silicon films

Abstract

Microcrystalline hydrogenated silicon films were produced at a high deposition rate of about 2 nm/s by using a capacitively coupled plasma under a practical pressure of around 1 kPa. The SiH4 source gas was almost fully dissociated when highly diluted with H2 gas, and the dominant species in the gas phase were found to be SiH3 radicals, which are film-growth precursors, and H atoms. The absolute density of these species was measured as the partial pressure of SiH4 gas was varied. With the increasing SiH4 gas flow rate, the SiH3 radical density, which was on the order of 1012 cm−3, increased linearly, while the H-atom density remained constant at about 1012 cm−3. The film growth mechanism was described in terms of precursors, based on the measured flux of SiH3 radicals and H atoms, and the relative fraction of higher-order radicals.