Correlation between highly and moderately accelerated electromigration tests

Electromigration testing at the wafer level under very highly accelerated stress conditions offers the potential for significant savings in cost and test time over less accelerated package-level tests. However, the extremely large current densities and high temperatures used to achieve that acceleration add uncertainties in extrapolating test results to operating conditions. Also, the possibility exists that failure mechanisms other than those of interest may be excited. Data are presented showing good correlation between wafer- and package-level electromigration test results for a particular metal system, namely, Al-Cu(2 wt.%) with a TiW top and bottom layer.<>