Water diffusion and fracture behavior in nano-porous low-k dielectric film stacks

Among various low-dielectric constant low-k materials under development, organosilicate glassesOSGs containing nanometer-size pores are leading candidates for use as intrametal dielectrics infuture microelectronics technologies. In this paper, we investigate the direct impact of waterdiffusion on the fracture behavior of film stacks that contain porous OSG coatings. We demonstratethat exposure of the film stacks to water causes significant degradation of the interfacial adhesionenergy, but that it has negligible effect on the cohesive fracture energy of the nanoporous OSG layer.Isotope tracer diffusion experiments combined with dynamic secondary ion mass spectroscopy showthat water diffuses predominantly along the interfaces, and not through the porous films. This unexpected result is attributed to the hydrophilic character of the interfaces.