The effect of water uptake on the mechanical properties of low-k organosilica glass

Abstract

Water uptake in porous low-k dielectrics has become a significant challenge for both back-end-of line integration and circuit reliability. The influence of absorbed water on the mechanical properties of plasma-enhanced chemical-vapor-deposited organosilicate glasses (SiCOH) was investigated with nanoindentation. The roles of physisorbed (α-bonded) and chemisorbed (β-bonded) water were examined separately through annealing at different temperatures. Nanoindentation measurements were performed on dehydrated organosilicate glass during exposure to varying humidity conditions. The elastic modulus and hardness for as-deposited SiCOH are intimately linked to the nature and concentration of the absorbed water in the dielectric. Under mild-annealing conditions, the water-related film mechanical property changes were shown to be reversible. The mechanical properties of UV-cured SiCOH were also shown to depend on absorbed water, but to a lesser extent because UV curing depopulates the hydrophilic chemical groups in SiCOH. High-load indentation tests showed that in-diffusion of water in the film/substrate interface can degrade the hardness of SiCOH/Si film stacks significantly, while not significantly changing the elastic modulus.

Citation

Guo, X.; Jakes, J.E.; Nichols, M.T.; Banna, S.; Nishi, Y.; Shohet, J.L. 2013. The effect of water uptake on the mechanical properties of low-k organosilica glass. J. Appl. Phys. Volume 114, 2013; pp. 084103-1 to 084103-11.