| Adhesion of Pt films to Si substrates with a native oxide has been investigated using two novel methods of quantitative adhesion characterization. The nanoindentation induced delamination method uses an impression to store compressive strain in an overlayer film to induce delamination at the Pt/SiO2 interface. Likewise, the telephone cord delamination method involves sputtering a thick compressively stressed overlayer onto the Pt/SiO2 films to induce telephone cord delamination patterns in the film. Crack energy release rates and interface toughnesses are calculated from the dimensions of the circular blisters or the telephone cords using currently available models. Focused ion beam (FIB) observations show that the nanoindentation method is difficult to implement because of extensive crack formation in the substrate beneath the indentation, causing interface toughnesses from this test to be gross overestimates. The telephone cord measurements, by comparison, give realistic interface toughnesses, allowing us to show that decreasing the argon pressure during Pt sputtering significantly increases the adhesion of the films to the substrate. Four-point bending experiments on the same interfaces were also conducted in order to compare the results with those of the telephone cord induced delamination method. The mechanism for the increased toughnesses of the interfaces as the argon sputtering pressure during Pt deposition was lowered was investigated as well. Results from XPS analysis shows that a more chemically diffuse interface is responsible. |
