Measurement of Electromigration Parameter Under Current-Ramp Stress

The measurement of current density exponent (n) is an extremely important parameter used for evaluating the lifetime of metallization in microelectronic devices. A new dynamic current-ramp method was developed to test the exponent n. It improved the accuracy and reduced test time by one or two orders of magnitude, comparing with the MTF method. The n four samples were measured under continuous DC, they were 2.29 (Al-Si alloy), 1.25 (Al-Si-Cu alloy), 1.28 (Al-Si/Ti two-level metallization) and 1.23 (Al-Si/TiWTi/AI-Si multilevel), respectively. These results proved that the values of n are dependent on materials and well agreed with that of the black equation. The exponent n was also studied under different test temperature and current-ramping slope.It is independent of temperatureand current-ramping slope in a wide range.