Extensive investigations of temperature influence on barrier integrity during reliability testing

Investigation of stress migration phenomena is one of the key aspects to characterize metallization reliability. Typical test methodologies are investigations of resistance shifts at wafer-level or package-level temperature storage tests under a temperature range between 150 °C and 275 °C. During these tests a very limited resistance increase dependent on the test structure is allowed. Most recently we encounter unusual resistance shift at the highest stress temperature which did not yield classical stress voiding detectable by failure analysis. We found changes in barrier integrity explaining the resistance shift by barrier oxidization. This has been verified by specially prepared material as well as extensive failure analysis investigation.