Influence of thickness and substrate on the hardness and deformation of TiN films

Titanium nitride films with thickness ranging from 0.2 to 1.4 mu m were deposited by an ion-assisted filtered area vapour deposition system onto single-crystal silicon, sapphire and a tool steel at room temperature. Precision force-displacement measurements of Berkovich indentations to various loads and depths of penetration were made on all the films. The film thickness was particularly critical for indentations on the softer substrates (silicon and tool steel) whereas for the films on the sapphire virtually no influence was detected. Analysis of the force-displacement data indicated a strong load dependence of the hardness and modulus for the films on the softer substrates. The deformation about and beneath the films was also examined with scanning electron microscopy observations of cross-sections. There was virtually no evidence of plastic deformation of the film.