The nanoindentation behaviour of hard and soft films on silicon substrates

Abstract

Carbon nitride and copper films of thickness 550 and 400 nm, respectively have been sputter deposited on silicon substrates. The indentation behaviour of these films is investigated by analysis of the load-displacement curves and by imaging of the residual indents. The Oliver and Pharr method is used to calculate the hardness from the load-displacement curve, while the contact area measured by atomic force microscopy is used in the traditional hardness equation: H= P/ A. The carbon nitride films exhibited neither pile-up nor sink-in behaviour and the hardnesses determined by both methods are very similar. The copper films showed pile-up at the indent edges at nearly all loads, and there is then a large difference between the hardness values measured by the two methods. Both films show the effect of the substrate on the hardness values as the indentation depth increases. In order to distinguish the “true” film hardness from the measured composite hardness, Korsunksy's composite hardness model is applied.