Structure and mechanical properties of PACVD fluorinated amorphous carbon films

Fluorinated amorphous carbon films were deposited by plasma assisted chemical vapour deposition from C2H2 and CF4 gases. Gas mixture and bias voltage were changed. We analysed film structure by Raman and infrared spectroscopies and film hardness by micro-indentation. Raman spectra show a transition from diamond-like carbon films to polymer-like films as the CF4 content in the plasma increases. The presence of a strong fluorescence background in the spectra of fluorine rich films indicates a polymer-like structure. Infrared spectra confirm the presence of -CFx, F2C=CF2 and F2C=C(HF) groups in the films. Hardness values are correlated with the trends of the D to G peak intensity ratio, I-D/I-G. Mechanisms involved in film growth and formation are discussed especially regarding fluorine substitution for hydrogen.