Comparison of isothermal, constant current and SWEAT wafer level EM testing methods

In this paper, we present data from three wafer level electromigration test techniques, isothermal, constant current, and standard wafer level electromigration accelerated test (SWEAT), and compare various aspects of the data. The isothermal method keeps the test line at a constant temperature by monitoring line resistance during test. The constant current method simply applies a constant current of the same magnitude to all lines, without making any adjustments for individual geometric differences. The SWEAT method holds the time to failure constant by using Black´s equation to determine the applied current needed to bring about the chosen failure time. Six different line widths ranging from 0.150 to 4.285 μm of AlCu metallization were stressed by all three methods, at temperatures from 300 to 380°C in 10°C steps