Characterization of Interfacial Mechanical Properties Using Wedge Indentation Method

Abstract

The objective of this thesis is to develop a simple experimental technique and a straight forward analysis procedure that can accurately measure the interfacial strength and toughness of the submicron thin film structures. Following the hypothetical operations of indentation-induced interface delamination introduced by Marshall and Evans, the analytical solution for interface toughness in terms of strain energy release rate is derived, where the indentation induced stress is found to be linearly proportional to the volume ratio of indentation volume and the volume of the film above the interface crack. Applications of the experiments and analysis of the wedge indentation method on low-k films and Ruthenium dioxide film have shown accurate and repeatable results. Furthermore, the results are consistent with the interfacial energy determined from the finite-element simulation of the wedge indentation induced delamination. In addition, the time-dependent fracture properties of the low-k films are studied using the wedge indentation method. It is found that the chemical structure of the low-k films has great influences on the crack growth during wedge indentation test. The wedge indentation tests on BlackDiamond (BD) films at ambient environment show that time-to-failure decreases exponentially with holding load, and a linear relation exists between loading rate and the onset of time-dependent fracture. On the other hand, the methysilsesquoxane (MSQ) film is relatively unaffected by the environment.