Preparation of (Ti 1− xAl x)N films from mixed alkoxide solutions by plasma CVD

Abstract

(Ti 1− x Al x )N films were prepared on a Si wafer at 700°C from toluene solution of alkoxides (titanium tetraetoxide and aluminum tri-butoxide) in an Ar/N 2/H 2 plasma by the thermal plasma chemical vapor deposition (CVD) method. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, electrical resistivity, and Vickers micro-hardness. Single phase TiN formed at an Al atomic fraction of 0–0.2, with a mixed TiN and AlN phase occurring up to 0.6 and single phase AlN forming above 0.8. The films had relatively sooth surfaces, 0.4 μm thick at an Al atomic fraction of 0.2, and thickened with increasing Al fraction. The atomic concentration of Ti, Al, N, O, and C determined from their respective XPS areas showed that the Ti and Al contents of the films changes with the solution composition in a complementary way. The impurities were about 10 at.% oxygen and carbon. The electrical resistivity was almost unchanged from the value of 10 3 μΩ cm at 0–0.6 Al but then suddenly increased to 10 4 μΩ cm at higher Al contents. The hardness showed a synergic maximum of about 20 GPa at an Al fraction of 0.6–0.8.