Water Diffusion and Fracture Behavior in Nano-Porous Low-K Dielectric Film Stacks

Abstract

Among various low-dielectric constant (‘low-k’) materials under development, organosilicate glasses (OSG) containing nanometer-size pores are leading candidates for use as intra-metal dielectrics in future microelectronics technologies. In this paper, we investigate the direct impact of water diffusion on the fracture behavior of film stacks that contain porous OSG coatings. We demonstrate that exposure of the film stacks to water causes significant degradation of the interfacial adhesion energy, 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 (SIMS) show that water diffuses predominantly along the interfaces, and not through the porous films. This unexpected result is attributed to the hydrophilic character of the interfaces.