RF PACVD DIAMOND-LIKE CARBON COATINGS ON INSULATING OBJECTS

Bias voltage variations along the surface of an insulating cylinder (h eight 5.5 cm) placed on a capacitively coupled powered electrode durin g the presence of an r.f. methane discharge are determined. The measur ement technique consists of analysing the IR absorption properties of the locally deposited amorphous hydrogenated carbon films along the 28 50-3300 cm-1 absorption band (C-H stretching vibration) and making use of a previously determined correlation between the bias voltage durin g film deposition and structural properties such as the sp3/sp2 C-H bo nding ratio, the bonded hydrogen content, etc. Various kinds of insula ting materials were selected covering a wide range of dielectric const ants: Teflon (epsilon(r) almost-equal-to 2), alumina Al2O3(epsilon(r) almost-equal-to 7) and rutile TiO2(epsilon(r) almost-equal-to 110). Th e experimental results suggest that the bias voltage variation across insulating objects is governed by their capacitance.