A method to measure the interfacial toughness of film/substrate by nanoindenter is proposed as the thickness of the film decreases, the measurement of the interfacial toughness requires the more sophisticated technique such as nanoindentation.
In this study, the nanoindenter is applied to the substrate very near the interface of film/substrate in the direction perpendicular to the normal of the interface, causing the cohesive fracture of the substrate, followed by the interfacial cracking. The length of the interfacial crack is measured, using the relation between the crack length and the displacement jump during the nanoindentation.
The specimen of Cu(0.56 μm)/Si(530 μm) are made by sputtering the copper onto the silicon wafer. By scratching the copper surface, we can make the easy interfacial cracking during the nanoindentation. It is found that the averaged values of the interfacial toughness of the Cu/Si is 0.664±0.3 J/㎡. The phase angle of the specimen in this study is $ψ\simeq-36.8˚$, computed by a method of Suo and Hutchinson(1990).