The growth mechanisms for the deposition of hydrocarbon films (C:H-films) from a methane electron cyclotron resonance (ECR) plasma are investigated by means of in-situ ellipsometry. Ion bombardment during plasma-enhanced chemical vapor deposition of hydrocarbon films mainly governs the properties of the films and the total growth rate. the role of ions for the growth rate and the film properties is discussed in this paper. Films were deposited with varying RF-bias, resulting in a DC self-bias ranging from floating potential up to 100 V. the ion-induced modification of the film properties was investigated by a new technique using a double layer consisting of a polymer-like film with low optical absorption and a hard carbon film with high absorption on top. the interface between these layers was analysed after deposition by a layer-by-layer etching in an oxygen plasma at floating potential. From these data it is possible to determine with high accuracy the range of the ion-induced modification of the optical properties in the underlying polymer-like film. the thickness of this modified layer ranges from 6 Å at 30 V self-bias to 40 Å at 100 V self-bias, which is consistent with the range of hydrogen ions in polymerlike films as calculated by the computer code TRIM.SP.
Based on the presented results, the growth of C:H-films and the resulting film properties can be modelled by the growth at activated sites at the film surface. these activated sites are represented by dangling bonds, induced by the ion bombardment. they also show up in the ellipsometric results during the deposition of C:H-films by a change of the optical response of the film surface.