Quantitative Measurements of Subcritical Debonding of Cu Films from Glass Substrates

A driver film method, in which a highly stressed overlayer is deposited to de-adhere a target film from a substrate, was developed to study the subcritical debonding behavior of Cu films from glass substrates. The driving force for debonding along Cu/glass interfaces was varied by depositing Cr overlayers to a range of thicknesses. One-dimensional crack growth was achieved by using C release layers and cutting strips from blanket films. Crack velocities, v, were measured and a wide strip solution was developed to obtain strain energy release rates, G. The Cu/Cr strips delaminated in a highly reproducible way, generating v–G plots similar to those seen in stress-corrosion cracking of bulk glass. Small variations in the amount of oxygen incorporated into the films during deposition strongly affected delamination rates. A reaction rate model for subcritical cracking by hydroxylation of the surfaces suggests that changes in oxygen content change the density of strong Cu–O–Si bonds across the interface.