Impact of pattern density on copper interconnects barrier metal liner integrity

The dependency of Cu interconnects barrier metal liner integrity due to neighboring pattern density is presented in this paper. It was found that TaN/Ta bi-layer barrier metal liner on isolated Cu interconnects was oxidized through electrical test and failure analysis. An elaborate study on the neighboring interconnects pattern density as well as process solutions were explored to investigate the impacts on the metal liner. Hypotheses were discussed. Results showed that there is an obvious pattern density correlation with the integrity of the metal liner. A comprehensive methodology was devised to check the process window of the metal liner process. The deduction is care needs to be taken in the design of interconnects circuitry. While metal liner process can be optimized, a balance is needed to ensure a robust and reliable barrier metal with neighboring interconnects pattern density.