Integration and characterization of gas cluster processing for copper interconnects electromigration improvement

Basic physical properties as well as electrical and reliability performance of Infusion™ processing were evaluated. This approach, proposed as an alternative to CuSiN and electrolessly deposited Co-alloys, was shown to join the benefits of these two techniques without well-known associated drawbacks. Indeed, it is a uniform process, acting as an efficient Cu diffusion barrier, which does not require specific integration development. Different processes were introduced in a multi-level interconnect stack using ULK/USG stack as IMD, showing excellent electrical properties, and three times electromigration time-to-failure improvement with respect to standard SiCN barrier. However, it was shown that existing process conditions lead to some introduction of N atoms into ULK dielectric, showing there is still some room for process optimization in architectures using un-capped ULKs, to keep the benefits of EM improvement and aggressive effective dielectric constant.