A study on the residual stress of diamond-like carbon films deposited by magnetically enhanced RF PECVD

Abstract

Hydrogenated DLC films were synthesized by RF plasma deposition with and without magnetic enhancement, and their film stresses were investigated as a function of process parameters. Under investigated process conditions, V-b/P-1/2 (where V-b is the self-bias voltage and P is the working pressure) is the appropriate scaling factor representing impinging ion energy. Film stress is influenced by not only ion impinging energy but also by ion to adspecies flux ratios. As ion energy increases, film stresses increase to a maximum value corresponding to the highest number of sp(3) carbon bonds. As ion/adspecies flux ratio increases, the maximum stress value decreases and the corresponding ion energy increases. Induction of a magnetic field promotes film stresses as high as 15.2 GPa, which is one of the highest value reported in hydrogenated DLC films. The magnetic-induced increase of stress can be explained by increased ion/adspecies flux ratio, thus, enhanced sp(3) formation. Rapid reduction of stresses observed at high ion energies may stem from the formation of graphite (sp(2) bond) phases. Inclusion of hydrogen in the films is not directly responsible for the stress generation.