Observation of boron nitride thin film delamination due to humidity

The effect of humidity on the delamination of boron nitride thin films on silicon substrates was investigated by measuring changes of the mean compressive stress within the films, as well as by light microscopic observations of the evolution of film delamination patterns under varying ambient humidity. The observed propagation velocities of delaminations and the resulting patterns of film buckles strongly depend on humidity. The film buckle patterns exhibit peculiar features which cannot be explained purely mechanically. The observation of separate film buckles in the immediate vicinity of large connected buckle patterns suggests that film adherence loss occurs by diffusion and chemical reaction of water at the film/substrate interface, possibly accompanied by volume expansion. On the other hand, the observed adherent film parts within buckle patterns, which sustain large humidity exposures, are proposed to be due to sufficiently rapid out-diffusion of reaction products, preventing adherence loss.