Electromigration characteristics of tungsten plug vias under pulseand bidirectional current stressing |
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Authors: | Tao J Young KK Pico CA Cheung NW Hu C |
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Affiliation: | Dept. of Electr. Eng. & Comput. Sci., California Univ., Berkeley, CA; |
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Abstract: | Using Kelvin test structures, electromigration performances of selective CVD tungsten filled vias under DC, pulsed DC, and AC current signals have been studied. The metallization consists of Al-Cu/TiW multilevel metals. The via electromigration lifetime exhibits a current polarity dependence. The via AC lifetimes are found to be much longer (more than 1000×) than DC lifetimes under the same peak stressing current density. The via lifetimes under pulsed DC stress of 50% duty factor are twice the DC lifetimes at low-frequency regions (<200 Hz) and 4-5 times the DC lifetimes at high-frequency regions (>10 kHz). The results are in agreement with the vacancy relation model |
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