Cavity ring down detection of SiH3 on the broadband à 2A1′ ← X̃ 2A1 transition in a remote Ar–H2–SiH4 plasma

Here we report on the use of the cavity ring down (CRD) technique for the detection of the silyl radical SiH3 on the broadband à 2A1′ ← X̃ 2A1 transition around 215 nm. SiH3 has been detected in a remote Ar–H2–SiH4 plasma during hydrogenated amorphous silicon (a-Si:H) thin film growth. The measurements demonstrate the capability of CRD to measure small broadband absorptions in the deep UV in the hostile environment of a deposition plasma. The SiH3 absorption shows an expected dependence on the SiH4 precursor flow and correlates well with the a-Si:H growth rate. The observed absorptions correspond with SiH3 densities in the range 2–13 × 1018 m−3, which is at least two orders of magnitude above the estimated SiH3 detection limit.