Delamination and Buckling Induced by Compressive Strain in Metal Thin Films

Abstract

The pattern formation during delamination and buckling in sputter-deposited tungsten thin films under large compressive stresses was investigated. The films were analyzed in situ by a cantilever beam technique, and ex situ by atomic force microscopy (AFM) and focused ion beam. Depending on the magnitude of compressive strain in thin films, different types of buckling patterns were observed. For stresses above a critical value, there was a regime of steady growth in which the incipient blister evolves into a regular sinusoidal-like propagation. At higher strains, the sinusoidallike wrinkles were developed with constant widths and wavelengths. Some of the wrinkles bifurcated to form branches. With further increase in stress the complicated buckling patches were formed with many irregular lobes. These types of pattern formation have been supported by elastic energy calculations.