Synthesis and characterization of carbon nitride thin films prepared by rf plasma enhanced chemical vapor deposition

Amorphous carbon nitride thin films were deposited on Si(100) wafers by radio frequency plasma enhanced chemical vapor deposition (PEVCD) with capacitively coupled plasma using NH3 and CH4 as precursors. The influence of the experimental parameters, i.e. the ratio of the NH3/CH4 flow rate, rf power, the deposition temperature and electrode spacing, on the film deposition rate and surface roughness of the films was investigated. The composition, surface morphology and film structure were analyzed by various techniques. The deposition rate was found to be affected by all parameters. In particular, at high deposition temperature or at high NH3/CH4 ratio, the deposition rate was reduced to almost zero. The nitrogen concentration increased rapidly with increasing NH3/CH4 ratio, which then saturated to a certain level (<20 at.%). It is believed that during film growth, the absorption/desorption processes on a substrate surface may play an important role. The sharp decrease in the RD with increasing NH3/CH4 ratio is ascribed to the local desorption of nitrogen in the nitrogen enriched regions or the formation of volatile CN compounds (e.g. C2N2), which also explains the limited amount of the maximum nitrogen content. The films consisted mainly of two hybridizations, N–sp2C and N–sp3C bonds, but the fraction of N–sp3C bonds decreased with increasing N content. The size of the sp2–C clusters in the films decreased with increasing N addition, suggesting that N incorporation can break the long-range order of the graphitic structure.