EFFECT OF METHANE HYDROGEN DILUTION ON THE PROPERTIES OF HYDROGENATED AMORPHOUS-CARBON FILMS DEPOSITED BY RF-PLASMA

The effects of methane dilution in hydrogen on the properties of hydrogenated amorphous carbon (a-C:H) films deposited by RF-plasma have been studied. The methane concentration varied from 100% to 5%, while the other technological parameters were kept constant. The films were characterized by spectroscopic ellipsometry, IR spectroscopy, thermal effusion spectrometry and electrical resistivity measurements. The effects produced by the gradual increase of the hydrogen concentration in the reactant gas were discussed in terms of the observed changes on a-C:H properties. The increase of the hydrogen in the precursor gas caused a reduction of the deposition rate, changing from deposition to etching when the hydrogen concentration exceeded 90%. Films maintained their amorphous structure, but their optical properties showed a dependence on the hydrogen concentration in the deposition plasma. This dependence is not due to a more effective hydrogen incorporation in the films, but rather to a reduction of double bonding in the amorphous carbon structure. © 1992.