CNxHy films obtained by ECR plasma activated CVD: The role of substrate bias (DC, RF) and some other deposition parameters in growth mechanisms

Electron cyclotron resonance (ECR) plasma activated CVD in CH4+N-2 gas mixt ure has been used to grow thin CNxHy films on steel or AI-Si alloy. The com position. optical and mechanical properties of the films deposited at vario us process conditions were investigated by electron microprobe analysis (EP MA), IR spectroscopy and microhardness measurements. It was shown that the DC bias does not influence substantially the films properties and such film s have a high nitrogen content (N/C similar to 0.6) and polymer-like struct ure. The RF bias changed drastically all the films properties. RF biased fi lms had a small nitrogen content (N/C similar to 0.2), were rather harder 4 000-7000 N/mm(2) (i.e. 4-7 GPa), all the bands on the IR spectra of the fil ms became very weak and some of them disappeared. This effect is explained by the ion bombardment influence, which may be effectively realised for die lectric CNxHy films only at RF biased substrate. Variation of RF biased CNx Hy film properties is related to the destruction of their polymer-like stru cture under the ion bombardment and formation of a highly disordered struct ure of the film on the base of graphite-like clusters containing the carbon and nitrogen atoms. The tribologically best CNxHy coatings prepared by the described method of ECR plasma activated CVD were achieved under RF bias U -RF about - 100 V and for lower ratio of N/C less than 0.2 in the films. (C ) 1999 Elsevier Science S.A. All rights reserved.