Fundamental understanding of porous low-k dielectric breakdown

We investigate the impact of porosity on the reliability of low-k dielectrics. We show that electric field enhancement around pores occurs and is significantly increased by Cu interaction, suggesting a new potential mechanism for breakdown of dielectrics at stress conditions. We develop of an analytic model to predict failure distribution parameters as a function of porosity and show that the model is in good agreement with measurements for porosity in the range of 5% to 40%. We explain why the field acceleration factor γ is a constant for all silica-based material according to percolation theory. We propose that the percolation path difference between high field and low field would make the field dependence on failure time become non-linear.