Radical species involved in hotwire (catalytic) deposition of hydrogenated amorphous silicon

Abstract

Threshold ionization mass spectroscopy is used to measure the radicals that cause deposition of hydrogenated amorphous silicon by “hotwire” (HW), or “catalytic,” chemical vapor deposition. We provide the probability of silane (SiH 4) decomposition on the HW, and of Si and H release from the HW. The depositing radicals, and H atoms, are measured versus conditions to obtain their radical-silane reaction rates and contributions to film growth. A 0.01–3 Pa range of silane pressures and 1400–2400 K range of HW temperatures were studied, encompassing optimum device production conditions. Si 2H 2 is the primary depositing radical under optimum conditions, accompanied by a few percent of Si atoms and a lot of H-atom reactions. Negligible SiH n radical production is observed and only a small flux of disilane is produced, but at the higher pressures some Si 3H n is observed. A Si–SiH 4 reaction rate coefficient of 1.65 ⁎ 10 − 11 cm 3/s and a H + SiH 4 reaction rate coefficient of 5 ⁎ 10 − 14 cm 3/s are measured.