Effect of Ta migration from sidewall barrier on leakage current in Cu/SiOCH low- k dielectrics

Tantalum migration from the anode sidewall barrier was observed in Cu interconnects/SiOCH low- k dielectrics after voltage ramp and constant voltage stress. This phenomenon was found to contribute to leakage current as observed from the current-voltage (I-V) and current-time (I-t) leakage curves. The mechanism of Ta migration is proposed to be due to the ease of Ta oxidation that converts the Ta atoms into ions, which subsequently drift along with the applied electric field and into the SiOCH low- k dielectric. The Ta ionic drift and diffusion into the dielectric led to an increase in leakage current, although the eventual formation of a stable Ta oxide resulted in a leakage saturation.