On the deposition mechanism of a-C:H films by plasma enhanced chemical vapor deposition

Amorphous hydrogenated carbon (a-C:H) films were deposited from a mixture of C2H2and Ar, by a radio frequency direct current (r.f.-d.c.) plasma-enhanced chemical vapor deposition technique. The effect of process parameters on the deposition rate of the a-C:H films was systematically studied. It was found that the deposition rate increased initially and then decreased after passing a maximum with the increase of bias voltage and deposition pressure. The deposition rate increased gradually with increasing C2H2content. However, a-C:H films could not be prepared at C2H2contents lower than 10%. A simple phenomenological surface model, which takes into account the sputtering effect of a-C:H films by energetic Ar ion bombardment, is proposed on the basis of these results to describe the deposition mechanism of a-C:H films.