A study of SiN cap NH3 plasma pre-treatment process on the PID, EM, GOI performance and BEOL defectivity in Cu dual damascene technology

The influence of the SiN cap-layer NH₃ pre-treatment process on the electromigration (EM), plasma-induced damage (PID), gate oxide integrity (GOI) and BEOL defectivity has been studied. A noteworthy trade-off between EM, PID, GOI performance, and BEOL defectivity is revealed. On one hand, aggressive NH₃ pre-treatment process yields improved EM lifetime and PID. On the other hand, the process may provoke Cu hillock and IMD blister defects, as well as GOI yield failure if the treatment is over-aggressive. These disparate observations have been satisfactorily explained using RF plasma-induced heating mechanism in the underlying Cu and IMD. This paper also shows the need to adjust the NH₃ pretreatment process to meet the overall yield, reliability and manufacturability requirements.