Chemical vapour deposition of diamond at low substrate temperatures using fluorinated precursors

Abstract

Diamond deposition from the fluorinated hydrocarbons CF 4 and CHF 3 was investigated in a hot filament chemical vapour deposition (HFCVD) system. The systems H 2CF 4, H 2CHF 3 and H 2CH 4 were compared under equivalent conditions. Our results demonstrate that below 650 °C the diamond growth rate for H 2CHF 3 gas mixtures is higher than that for the H 2CH 4 system. Even at 400 °C it was possible using H 2CHF 3 to measure considerable growth rates with in situ laser interferometry. Mass spectrometry proved the formation of HF at a significant concentration for the system H 2CHF 3. This is due to the abstraction of F from CHF 3 by atomic hydrogen. CF x radical species are postulated from CHEMKIN calculations. They are supposed to play an important role in the diamond growth process using CHF 3. With H 2CF 4 mixtures neither diamond nor amorphous graphitic carbon could be deposited. Mass spectrometry showed the inertness of CF 4 under the conditions of our investigations with the absence of the F abstraction reaction.