True constant temperature MTF system for the characterization of electromigration of thick Cu interconnection lines

A new measurement system for performing MTF (Median Time to Failure) tests on packaged samples of metallic interconnection lines is presented. The system allows to maintain the sample current and temperature exactly constant throughout the entire duration of the test. This is obtained by employing a separate thermal unit for each single sample and a temperature control algorithm which allows to compensate for the increase of the self heating which is the result of the unpredictable resistance increase caused by the accumulated EM damage. This feature may be particularly interesting in the case of thick Cu interconnect lines because of the relevant self heating that is the result of the high currents needed to obtain significant damage in a reasonably short test time.