Amorphous carbon film deposition using a DC-biased screen-grid in an electron cyclotron resonance plasma

Abstract

The deposition of hydrogenated amorphous carbon (a-C:H) films from a mixture of hydrogen and methane using the electron cyclotron resonance chemical vapour deposition (ECR–CVD) method is reported. A screen grid positioned above the substrate was used to provide an electric field to accelerate the ions towards the substrate during deposition. The structural characteristics of the a-C:H films have been studied using Raman spectroscopy. The effects of DC bias applied to the screen grid on the Raman spectra, hardness and optical gap were investigated. Under conditions of 400 W microwave power and 6.5 mTorr process pressure, Raman scattering analysis showed that the film characteristic changes from diamond-like to more graphite-like as the grid voltage was increased from −100 V to −600 V. The variation of the D and G line peak positions and the integrated intensity ratio (I D⧹I G) in the Raman spectra showed good correlation with the film harness and optical gap profiles. Our results showed that the screen grid method is effective in controlling the ion energy through varying the grid voltage. An increase in the grid voltage causes an increase in the ion energy leading to films which are more graphite-like.