Towards the understanding of intrinsic degradation and breakdown mechanisms of a SiOCH low-k dielectric

Degradation and breakdown mechanisms of a SiOCH low-k material with k=2.3 (25% porosity) and thicknesses ranging from 90nm to 20nm were investigated. By combining time dependent dielectric breakdown (TDDB) data at positive/negative bias stress with thickness scaling results, dielectric failure is proven to be intrinsic and not influenced by copper drift or barrier deposition induced dielectric damage, which is further demonstrated by a very low TDDB thermal activation energy. During dielectric degradation, low field leakage current increase is suggested to be caused by donor type trap generation. It is shown that stress induced leakage current (SILC) can be used as a measure of dielectric degradation. Therefore, by monitoring SILC, low field lifetime can be safely estimated using extrapolation. Based on our experimental results, it is suggested that the impact damage model has a better accuracy for low field lifetime prediction.