A new wafer-level isothermal Joule-heated electromigration test for rapid testing of integrated-circuit interconnect

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Abstract
We report on a new wafer-level isothermal Joule-heated electromigration test which allows rapid testing of integrated-circuit interconnects. This test can be used to investigate the temperature dependence of electromigration lifetimes. As a demonstration of the test, lifetimes of Al-1% Si lines were measured over the temperature range 200–400 °C. The lifetime results are consistent with an inverse-square current dependence and with an activation energy of 1.4 eV at higher temperatures (above about 345 °C) and 0.6 eV at lower temperatures. This is in agreement with a model of grain-boundary diffusion dominating the transport at lower temperatures with bulk diffusion dominating at higher temperatures. Numerical thermal models for Joule-heated test lines are used to investigate deviations from isothermal conditions for several practical situations. Various rapid electromigration tests are compared, and we show this new test can obtain the maximum possible electromigration lifetime test acceleration, while restricting test conditions to the lower-temperature grain-boundary dominated transport.