Abstract. The presence of excited radicals in plasma-assisted chemical vapour deposition silane processes leads to overestimation of radical densities in threshold ionization mass spectrometry analysis. A method to discriminate the signal due to excited radicals is proposed and applied to estimate the relative density trends of the ground-state silane radicals (SiH_x, x < 4) with hydrogen input flow rates (0–50 sccm) in an argon–silane–hydrogen plasma at total pressures of 0.01–0.04 mbar used for the deposition of nano-crystalline silicon (nc-Si) layers for photovoltaic applications. The SiH_x/SiH₄ density trends with hydrogen input show a turning point where SiH becomes dominant, in the process region where nc-Si layers were previously obtained.

Print publication: Issue 7 (7 April 2009)
Received 28 November 2008, in final form 19 January 2009
Published 13 March 2009