Aluminum Electromigration Lifetime Variations with Linewidth: The Effects of Changing Stress Conditions (Metallization for Integrated Circuits)

摘要

The electromigration behavior of aluminum in films deposited by In-Source evaporation has been examined for films with widths ranging from 2 to 5 mu m and lengths ranging from 30 to 80 cm. The linewidth dependence of the lifetime was obtained for films subjected to steady direct-current stressing as well as for films subjected to pulsed-current stressing. The results indicate that the observed linewidth dependence is a function of the nature of the accelerated aging method employed. Those samples subjected to high-frequency, (2MHz), low-duty-cycle pulses showed less linewidth dependence for lifetime than did those subjected to high-duty-cycle and steady direct-current stressing. Measurements utilizing pulse nonlinearity testing show a correlation between the onset of degradation as evidenced by a change in the thermal time constant, and the nature of the applied current-stress tests is proposed which may more accurately predict metallization lifetime under actual use conditions. (ERA citation 08:034248)