AN INFLUENCE OF A BIAS POTENTIAL ON THE PROPERTIES OF SI–C–N FILMS OBTAINED BY PLASMA ENHANCED CHEMICAL VAPOR DEPOSITION ONTO SILICON FROM HEKSAMETILDISILASANE

Abstract

To obtain silicon carbide-nitride thin films (Si–C–N) which in the best way connecting properties of silicon carbide, silicon nitride and carbon nitride are involved a lot of different methods, which explains the great interest to them. The Si–C–N films presented here have been obtained from a safe and affordable precursor hexamethyldisilazane (C6H19NSi2) by plasma-chemical equipment with two high frequency generators. The feature of plasma chemical technology with two plasma-generated sources is an availability to obtain a bias that can be controlled to little values. A substrate bias was changed according to the technical ability of PECVD equipment in the range from –5 V till –300 V. All other values of the parameters were fixed and chosen from experience of previous Õ-ray diffraction, atomic force microscopy, infrared spectroscopy Õ-ray photoelectron spectroscopy and nanoindentation. It was established, the substrate bias voltage did not significantly affect on the structure of Si–C–N films. They have leave Õ-ray amorphous even after hightemperature (1000 °C) vacuum annealing. A bias is not significantly affect on the mean square roughness Rq values which not exceed 0.598 nm and are comparable with the silicon substrate surface roughness (Rq ~0.4 nm) before deposition. Increase of the bias voltage promotes to grow of plasmachemical deposition rate of Si–C–N films from 0.65 Å/s at a minimal bias –5 V to 1.75 Å/s at a maximal bias –300 V. It is ability to control for the mechanical properties such as nanohardness and elastic modulus by substrate bias. The films obtained at minimal bias –5 V had a less value of nanohardness and elastically modulus (15 GPa and 165 GPa, respectively) in comparison with the films obtained at higher (–250 V) bias (27 GPa and 190 GPa, respectively). The increase of hardness of amorphous Si–C–N films with increase the bias voltage can be explained by changing of chemical bonding state. In particular, it is watched an increasing of Si–C bonds concentration when the concentration of Si–O bonds markedly decrease (the bias leads to obtain little oxygen structure). The obtained results in this work indicated the prospects of using native precursor hexamethyldisilazane to feature study with obtaining Si–C–N materials by plasma-chemical deposition to create new type of protective and wear resistant thin films materials.