Reliability improvement using buried capping layer in advanced interconnects

Electrical leakage and breakdown characteristics of low-dielectric constant (low-k) dielectrics are increasingly becoming major reliability issues as inter-metals spacings in interconnects are scaled towards the 0.1 mum technology node. These issues are greatly alleviated by the implementation of a buried capping layer (BCL) in Cu damascene structures. It is found that a BCL of 100 Angstrom thickness in Cu/SiOC interdigitated comb structures reduces the leakage current by I order of magnitude and improves breakdown strength by a factor of 1.5 to 2. In addition, the BCL is able to suppress the formation of process-induced traps in the low-k dielectric. These findings can have important reliability considerations for Cu/low-k integration schemes. [Keywords: interconnects, low-k, leakage current, conduction mechanism, dielectric breakdown.]