Residual stress effects in the scratch adhesion testing of tantalum thin films

The effect of residual stress on the scratch adhesion critical load has been measured for sputtered tantalum films. In this single metallurgical system, six different failure modes could be observed, ranging from ductile ploughing to extensive spallation. For tantalum films deposited on silicon substrates, a 15% decrease in critical load was observed as the film residual stress increased from -1.1 GPa to +1.0 GPa. A larger percentage decrease (50%) was observed for film deposited on softer AIMg/NiP substrates. Film spallation was more extensive from films deposited over a thin carbon layer and for these films critical with existing quantitative modes for the scratch adhesion test and indicate that failure by shear at the film-substrate interface can be more important than failure by compressive buckling.