Physical and mechanical properties of reactively sputtered chromium boron nitride thin films

This paper reports on the first study of physical and mechanical properties of reactively sputtered chromium boron nitride coatings as a function of chemical composition, bias voltage and substrate temperature. Several sets of coatings were deposited by reactive unbalanced magnetron sputtering on Si(100) substrates. The chemical composition was deduced from X-ray photoelectron spectroscopy and Auger electron spectroscopy measurements, and was found to be influenced primarily by nitrogen flow rate. The phase composition was determined using X-ray diffraction in conjunction with spectroscopic ellipsometry. Atomic force microscopy was utilized to determine surface roughness and average surface grain size. Both surface roughness and surface grain size were largely independent of the nitrogen concentration and decreased with increasing bias voltage. The nanohardness and elastic modulus of each sample were measured by nanoindentation. The hardest films were produced using −150 V bias voltage and either very low (0.5-1 sccm) or very high (12-15 sccm) nitrogen flow rates.