EVIDENCE OF ENHANCED ATOMIC-HYDROGEN PRODUCTION WITH HALOGENS IN DIAMOND MWPACVD

Optical emission spectroscopy measurements and exhaust gas mass spectr ometry were used for diagnostics in a microwave plasma assisted chemic al vapor deposition reactor for diamond growth. An actinometry techniq ue was used to study the atomic hydrogen generation with additions of CF4 and CCl2F2 in the feed gas. The relative emission intensity of the atomic hydrogen line H-alpha (656.3 nm) was measured with CF4 and CCl 2F2 concentrations in the range of 0-5%. The results show an increase in atomic hydrogen concentration up to 80 and 200% when CF4 and CCl2F2 are added in the mixture, respectively. The ideal actinometry conditi ons and the validity of the observed increase of atomic hydrogen with an change in electron temperature and density in the plasma was invest igated. The dissociation process of CF4 and CCl2F2 associated with HF and HCl formation were discussed by measurements of stable species by mass spectrometry of the exhaust gas. The increase of the atomic hydro gen concentration is correlated with the easy HCl and/or HF dissociati on by electron-impact. (C) 1998 Elsevier Science S.A.