Electromigration Reliability Assessment of Cu-based Metallization Systems by a Wafer-Level Approach

Recently, a fast improved isothermal method (ISOT) has been devised to characterize the electromigration (EM) wafer level reliability (WLR). In this paper, the usefulness of ISOT will be shown, not only for the aim of process monitoring in production, but also, when the method is applied carefully, to complement and, in perspective, to substitute the expensive standard package-level reliability (PLR) tests, currently used to assess the EM reliability. The complete methodological approach is described, as well as precautions to control the stress conditions and normalization procedures to account for the process parameter spread. Some results on double-damascene 90 nm Cu technology are shown.