Nanomechanical properties of silicon-, oxygen- and nitrogen-containing a-C:H films prepared by RF plasma beam CVD

The mechanical properties like hardness and reduced modulus of Si-, SiOx- and SiNx-containing a-C:H films (denoted as DLCSi, DLCSiO and DLCSiN), deposited respectively from tetramethylsilane, hexamethyldisiloxane and hexamethyldisilazane precursors onto silicon wafer by electron cyclotron wave resonance (ECWR) RF plasma beam CVD, have been determined by nanoindentation method. Relationships have been established between the nanomechanical properties and the self-bias developed during deposition, as well as the chemical structural parameters determined previously by X-ray photoelectron spectroscopy and X-ray induced Auger electron spectroscopy. In particular, an increase of the self-bias up to about 200 V during deposition led to a significant increase in the hardness of the layers. The hardness had a tendency to decrease with increasing O-content, and to increase with the increase of the modified Auger parameter for Si. The latter was attributed to the increase in the degree of crosslinking. For the first time, the hardness was found to increase with the increase of the bulk plasmon loss energy of the C 1s peak, which was interpreted in terms of the increase in the mass density.