Production and Detection of H Atoms and Vibrationally Excited H2 Molecules in CVD Processes

Radical species, including atomic hydrogen, play an important role in the CVD process to prepare high-quality thin solid films. Detailed information on the absolute densities of these radicals under various conditions is needed in order to understand the chemical kinetics involved and to control the deposition processes. This article reviews the production mechanisms and the gas-phase diagnostic techniques for H atoms in catalytic CVD (also called hot-wire CVD) and plasma-enhanced (PE) CVD processes. Experimentally determined absolute H-atom densities in typical CVD processes are compiled in a table. Under suitable conditions, the steady-state H-atom density can be increased up to 10(17) cm(-3). Procedures for producing and detecting vibrationally excited H-2 molecules, which can be another active species in CVD processes, are also discussed.