Studies of the sputter deposition of carbon, silicon and SiC films

Abstract

Abstract The sputtering behaviour of carbon, silicon and SiC targets in an r.f. system of power 1.5 kW was investigated. The influence of various sputtering parameters on the sputtering rate, the hardness, the adherence and the composition of films was studied using optical and electron microscopy, interferometry, X-ray and electron diffraction, IR spectroscopy, electron probe microanalysis and electron spectroscopy for chemical analysis (ESCA). Under comparable conditions silicon sputters more than twice as fast as carbon while the sputtering rate of SiC is between those of carbon and silicon. The rate shows a quadratic dependence on the target voltage and linear dependences on the power density and the pressure of the sputtering gas. Bias sputtering improves the microhardness only in the optimum range between −50 and −100 V, but it reduces the deposition rate. Diffraction experiments show all the films to be amorphous. Cosputtering of carbon and silicon results in a compaction of the sandwich film. An explanation based on the mass, the density, the cohesive energy and the energy transfer coefficient of the target is proposed to account for differences in sputtering rate between the target materials. Films prepared from SiC powder compact targets largely retain the target composition but are strongly influenced by oxide impurities in the target. Evidence is presented that the sputtering process involves free-atom reactions on the substrate surface. ESCA experiments show that the uppermost layers of SiC films are somewhat different in composition from the bulk of the films.