Effect of solution pH on the accelerated cracking of nanoporous thin-film glasses

Hybrid organic–inorganic nanoporous thin-film glasses are extremely fragile and prone to stress-corrosion cracking in reactive environments. This has limited their integration as ultra low dielectric constant layers in high density integrated circuits. We demonstrate how crack growth is influenced by non-buffered aqueous solutions and show that with increasing pH, crack-growth rates are significantly accelerated. Interestingly, a crack growth regime limited by the transport of hydroxide ions to the crack tip was observed. Existing models commonly used to predict crack growth are shown to over estimate the experimental data by 6 orders of magnitude. We rationalize this behavior in terms of a significant difference in the crack tip solution chemistry as compared to that of the bulk and propose both chemical reaction and transport mechanisms to support this hypothesis.