Plasma deposition of carbon layer: Correlations between plasma parameters, film structure and properties

The links between plasma parameters, discharge, film structure and properties are not really yet understood for amorphous hydrogenated carbon layers (a-C:H) plasma deposition. Here, a-C:H layers are deposited in a dual radio-frequency–multipolar microwave plasma excited by distributed electron cyclotron resonance reactor at low CH4 pressure. This study deals with the plasma analysis, the film characterization and with plasma parameters effect on a-C:H films deposition, structure and properties.The discharge analysis shows that CH4 is decomposed in CHy1 + H radicals and that C2H2y2 are present in the discharge. As at low pressure, recombination can only take place on the surface, C2 H2y2 desorbs from the surface. Moreover, C2 species are observed attributed to C2 H2y2 dissociation. The evolution of film composition with plasma power shows that the proportion of sp2 CC decreases in contrast with those of CH bonds which increases. From these observations, a phenomenological model for a-C:H deposition can be proposed. Finally, properties are correlated with the film structure and the effect of MW plasma power can then be given.