PRECURSOR GAS EFFECT ON THE STRUCTURE AND PROPERTIES OF DIAMOND-LIKE CARBON-FILMS

The effect of precursor gases on the diamond-like carbon (DLC) film deposition was investigated in the r.f. plasma-assisted CVD method. DLC films were deposited using methane or benzene as the precursor gas. The residual stresses, hardnesses, total hydrogen concentrations and electron energy loss spectra were compared at the same value of V(b)/P1/2. (Here, V(b) is the self-bias voltage of cathode and P the deposition pressure.) The values of V(b)/P1/2 ranges from 33 to 250 V mTorr-1/2 for methane and from 33 to 900 V mTorr-1/2 for benzene by changing the negative bias voltage from -100 to -900 V and deposition pressure from 1 to 100 mTorr. We observed significant differences between the structures and properties of these films. In the same range of V(b)/P1/2 the structure and properties of films deposited from benzene show characteristic behaviors of lower energy deposition than those from methane. The present observations are discussed in terms of the difference in the ion energy per carbon atom at the growth surface. The total hydrogen concentration in the films deposited from benzene is smaller by about 7 at.% in this experimental range.