Gas phase study with CF4 and CCl2F2 addition in microwave CVD diamond growth

Abstract

The effects of halogenated precursor associated with O 2 addition in the gas phase for diamond growth have been studied. Optical emission spectroscopy (OES) and exhaust gas mass spectrometry (MS) were used in a microwave plasma-assisted chemical vapor deposition (MWPACVD) reactor. The relative emission intensity of atomic hydrogen line H α (656.3 nm) has been measured with CF 4 and CCl 2 F 2 concentrations in the range of 0–5%. Our results show an increase of atomic hydrogen concentration up to 80 and 200% when CF 4 and CCl 2 F 2 are added in the mixture, respectively. The input gases were chosen in order to discern the oxygen effects for mixtures with different concentrations of CF 4 and CCl 2 F 2 . An additional increase of 50% H generation was observed when O 2 was added in the range of 0–3% for both mixtures with 3% of CF 4 or CCl 2 F 2 . Mass spectrometry was used to analyze the dissociation process of CF 4 and CCl 2 F 2 associated with HF and HCl formation. These dissociation processes are correlated with the increase of atomic hydrogen concentration. For oxygen addition, CO formation is the main final product from the halocarbon. The higher thermodynamic stability of CO enables us to obtain a gas phase with a high concentration of atomic hydrogen and inhibits the formation of solid non-diamond carbon observed in mixtures with high halocarbon concentrations.