Extrapolation of highly accelerated electromigration tests on copper to operation conditions

Compared to aluminum the electromigration resistance of copper is higher. This leads to longer test times. Higher acceleration factors are needed to reach reasonable test times. Because of the oven hardware there is a limitation in the stress temperature for standard iso-current tests on package level at 350°C. Self-heated test methods, such as SWEAT and accelerated iso-current test on wafer level, use Joule-heating to to reach stress temperatures up to 600°C and therefore to much lower test times. For aluminum a qualitative analysis with these tests has already been conducted successfully. It would be a major advantage, if quantitative analysis, e.g. extrapolation to operation conditions, would be feasible. During this investigation, we have used three different electromigration stress methods, iso-current test on package level, iso-current test on wafer level and SWEAT, with different stress conditions on the same structure and material. We show an extrapolation of all of the results of the different test methods to operation conditions and a way to calculate the necessary Black´s parameters from the results of the highly accelerated self-heated tests.