On the physical interpretation of the impact damage model in TDDB of low-k dielectrics

In one of the new “root-E” models for TDDB, there is a second term in the exponent representing the probability that there is enough energy to create damage that contributes to breakdown failure. This provides an exponential “1/E” character to the extrapolation to use conditions that predicts lifetimes many orders of magnitude longer than the simple root-E extrapolation. It also predicts a threshold voltage for damage independent of the applied field. It is argued here that the requirement for damage may not be the energy, but the momentum transfer to cause physical damage. The consequences are discussed.