Stress induced delamination methods for the study of adhesion of Pt thin films to Si

Abstract

Adhesion of Pt films to Si substrates with a native oxide has been investigated using two 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/SiO 2 interface. Likewise, the telephone cord delamination method involves sputtering a thick compressively stressed overlayer onto the Pt/SiO 2 films to induce telephone cord delamination patterns in the Pt film. Crack extension forces and interface toughnesses are calculated from the dimensions of the circular blister 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.