Influence of substrate bias on composition and structure of reactively r.f.-sputtered TiC films

• Published in: Thin solid films 1981-06, Vol.80 (1), p.77-83
• Main Authors: Sundgren, J.-E., Johansson, B.-O., Karlsson, S.-E.
• Format: Article
• Language: English
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/0040-6090(81)90209-1

TiC films were grown by reactive r.f. sputtering of titanium in methane onto negatively biased substrates. The composition of the films was measured using Auger electron spectroscopy in combination with depth profiling and the structure was revealed using X-ray diffraction. The carbon-to-titanium ratio was found to be 0.98 at zero bias voltage. It increases with bias voltage up to -200 V where it reaches a maximum of 1.08. As the bias is further increased the ratio decreases and approaches 1.00 at -500 V. These results show that in addition to the reaction on the target surface that occurs during the reactive sputtering process a reaction at the substrate surface must also occur. This is in agreement with earlier reported results in which the composition of both the films and the target surfaces was determined for different methane partial pressures. The reaction at the substrate surface is discussed in terms of ionization and reaction probabilities of methane molecules and in terms of resputtering effects. Owing to the increasing ion bombardment of the films with increasing bias voltage a change in crystal structure was obtained. The grain size decreased from 400 Å at zero bias to about 150 Å at -500 V. A variation in the lattice parameter was also found, a maximum being reached at a bias between -200 and -300 V.