Effects of Interlayers on the Scratch Adhesion Performance of Ultra-Thin Films of Copper and Gold on Silicon Substrates

Scratch testing has long been used to assess the adhesion of a film to its substrate. As film thicknesses have decreased, the need for greater precision and sensitivity in the scratch testing apparatus has increased. To this end, a nanoindenter was modified to make finely controlled, low-load scratches. Scratches at various loads and two orientations of a Berkovich scratching diamond were made in films of 100 nm of gold and 200 nm of copper, each on single crystal silicon. For each film type, samples with no interlayer, with an SiO2 interlayer, and with a TiW on SiO2 interlayer were tested. The scratch morphology was found to vary in a regular way with load, diamond orientation and interlayer material.