Influence of deposition parameters on the internal stress in a-C:H films

Amorphous hydrogenated carbon (a-C:H) films were deposited from a mixture of C2H2 and Ar by the r.f plasma-enhanced chemical vapor deposition technique. The internal stress was measured by the substrate bending method. The films were characterized by IR and positron annihilation spectroscopies. The influence of substrate bias and C2H2 content in the feedgas on the internal stress and structure were studied. It was found that the hydrogen content and sp(3)/sp(2) ratio decrease with an increase in substrate bias and a decrease in C2H2 content in the feedgas. However, the variations in H content and sp(3)/sp(2) ratio with C2H2 content are much less than that with substrate bias. The void density, which increases monotonically with the increase of C2H2 content, initially decreases and then increases with the increase of substrate bias. The internal stress in a-C:H films decreases with the increase of substrate bias and C2H2 content in the feedgas. The decreases of the H content and sp3/sp2 ratio in the films are the main factors that cause the reduction in internal stress. The void density has a minor effect on the internal stress. (C) 1999 Elsevier Science S.A. All rights reserved.