Laser Optogalvanic Monitoring of SiH in a Chemical Vapor Deposition Glow Discharge

A demountable hollow cathode discharge cell that is useful for studies of plasmas relevant to chemical vapor deposition (CVD) was assembled and demonstrated. Direct current glow discharge decomposition of 10% silane in helium in this cell at 20 Torr produced silicon-containing cathodic thin films that were subsequently examined with the use of Raman and x-ray fluorescence spectroscopy. A pulsed dye laser-excited optogalvanic detection technique was used to monitor the presence of a transient molecular intermediate—silicon hydride—in this decomposition plasma. An optogalvanic spectrum of the SiH A²δ -X²τ transition near 420 nm is presented. This electronic absorption technique complements other spectroscopic methods for mechanistic studies and optimization of glow discharge CVD plasmas that are currently used for the commercial preparation of technologically important thin film materials such as hydrogenated amorphous silicon. It will be particularly useful for detection of nonluminescent plasma intermediates.