DC bias effects in the deposition of a-C:H films using the screen-grid method in electron cyclotron resonance chemical vapour deposition

Abstract

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 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 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 hardness 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.