In this paper, we investigate low-k dielectric degradation process under bipolar voltage stress and thermal anneal. We study dielectric breakdown lifetime tBD, charge to breakdown QBD and conduction current I during dielectric degradation process. Compared with conventional CV (constant voltage) TDDB, bipolar TDDB has up to 2–3x lifetime increase. We find the change of leakage current ΔI/I per polarity switch and its changing rate have correlation with bipolar TDDB lifetime. Our study on bipolar TDDB with thermal anneal inserted in low-k degradation process shows there is no direct correlation between low voltage leakage current recovery and high stress TDDB lifetime. We find there is a correlation between the recovery of ΔI/I per polarity switch and bipolar TDDB lifetime enhancement. For system studied here the bipolar TDDB leakage current profile data show the centroid of trapped charge moves from anode side to the center line of dielectric as dielectric degrades. Using empirical fitting we build a simple model to simulate leakage current with major characteristics reproduced.