Progressive debonding of multilayer interconnect structures

Progressive (or time dependent) debonding of interfaces poses serious problems in interconnect structures involving multilayer thin films stacks. The existence of such subcritical debonding associated with environmentally assisted crack-growth processes is examined for a TiN/SiO2 interface commonly encountered in interconnect structures. The rate of debond extension is found to be sensitive to the mechanical driving force as well as the interface morphology, chemistry, and yielding of adjacent ductile layers. In order to investigate the effect of interconnect structure, particularly the effect of an adjacent ductile AI-Cu layer, on subcritical debonding along the TiN/SiO2 interface, a set of samples was prepared with AI-Cu layer thicknesses varying from 0.2-4.0 mu m. All other processing conditions remained the same over the entire sample run. Results showed that for a given crack growth velocity, the debond driving force scaled with AI-Cu layer thickness. Normalizing the data by the critical adhesion energy allowed a universal subcritical debond rate curve to be derived.