Line Edge Roughness of Metal Lines and Time-Dependent Dielectric Breakdown Characteristics of Low-k Interconnect Dielectrics

We present both experimentally and numerically the effect of the line edge roughness (LER) of metal lines on breakdown characteristics of low-k interconnect dielectrics. Experimental results show that the LER-induced metal-to-metal space variation significantly affects the Weibull slope, field acceleration parameter and hence the time-dependent dielectric breakdown (TDDB) reliability lifetime of sub-100 nm metal-to-metal spacing interconnects. For detailed quantitative explanation of the effect, we have developed a Monte Carlo simulation model, calibrated to experimental results, and performed a number of Monte Carlo simulations under various conditions. Both experimental and numerical simulation results support that lithography and dry etch processes affecting LER are of great importance to ensure robust low-k TDDB reliability of aggressively scaled interconnects.