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

Among various low-dielectric constant
low-k materials under development, organosilicate glasses

OSGs containing nanometer-size pores are leading candidates for use as intrametal 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 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.