Time-dependent dielectric breakdown is quickly becoming a very important topic as low-k materials are integrated into back-end-of-the-line processes and as interconnect dielectric thicknesses approach the sub-100-nm range. There still exists a considerable amount of debate on the dominant failure mechanism with or without the presence of a diffusion barrier. We have developed a series of models for copper-accelerated time-to-failure that we are using to guide an experimental program to understand failure mechanisms. The models are based on the injection and drift of copper ions and focus on an increase in the local electric field that allows electrons to enter the dielectric’s conduction band. The models are successful at correlating the time-to-failure for SiO2 dielectrics with and without barriers. The most important aspects of the model that we are trying to verify experimentally include the role of moisture in the dielectric oxidizing Cu to form injectable ions, the initiation of failure at the pore–matrix interface in porous dielectrics, a decrease in the time-to-failure in porous dielectrics due to an increase in Cu solubility, and the need for near-perfect barriers to realize the advantage of using a barrier. The key unknown parameters in all these models are the diffusivities and solubilities of copper ions in the materials. Models of this type are not restricted to just interlayer dielectrics. Several failure mechanisms associated with semiconducting and organic light emitting diodes may also be described by similar models.