Two-step improvement of electromigration lifetime under high-frequency pulsed conditions

Experimental evidence is presented of a marked improvement in electromigration (EM) lifetime under pulsed conditions above 1 MHz. Pulsed stress tests extending over a wide frequency range from 0.01 Hz to 50 MHz show that EM lifetime increases with (duty ratio)/sup -2/ under pulsed conditions in the kilohertz region and that an even further increase occurs in the megahertz region with (duty ratio)/sup -3/. This two-step behavior is analyzed by postulating two distinct relaxation processes. Relaxation times for the two processes are estimated to be about 5 s and 1 mu s.<
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