Effect of porosity on reducing cohesive strength and accelerating crack growth in ultra low-k thin-films [IC interconnect applications]

The reliable fabrication of interconnects containing nanoporous low dielectric constant (LKD) films has proven to be a significant technological challenge. The LKDs are brittle in nature and susceptible to stress corrosion cracking in reactive aqueous environments. Moreover, nearly all levels of processing involve subjecting these extremely fragile materials to mechanical loads in the presence of harsh aqueous solutions, such as chemical mechanical planarization (CMP). Here we demonstrate how controlled volume fractions of nanometer scale porosity reduces the cohesive strength of LKDs and significantly accelerates the rate of crack growth in both simulated and commercial CMP solutions.