Effect of reduced current density stress on the results of isothermal electromigration test for Cu single damascene line

Isothermal (ISOT) EM tests offer a fast method to evaluate metal EM degradation rate and reduced total test cycle times and costs. As in any highly accelerated testing, "overstressing" is a concern and should be avoided. In this work, we reduced the stress current density required, to achieve the desired self-heating by raising the temperature of the hot chuck. Comparison of various aspects of ISOT results on Cu single damascene lines such as resistance degradation profile, activation energy, and physical failure modes are presented. There is no significant change in these aspects due to reduced current density stress, which suggests no evidence that "over-stress" has occurred.