A Novel Al/TiN/CVD-W Structure to Eliminate Resistance Anomaly in Deep Submicron Al/CVD-W Interconnects

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Abstract
The sheet resistance increase of Al/chemical vapor deposition (CVD)-W interconnects after low-temperature annealing has been investigated. Anomalous sheet resistance increase depending on the linewidth in sub-half-micron Al-Si-Cu/CVD-W lines after 450° C annealing is found for the first time. The sheet resistance increase of the Al/CVD-W lines becomes larger for narrower linewidth after annealing. It is considered that this anomalous sheet resistance increase is due to more nonuniform high-resistivity WAl12 formation in the narrower lines. Using a TiN interlayer to eliminate WAl12 formation, sub-half-micron lines of a new Al-Si-Cu/TiN/CVD-W structure have demonstrated sufficiently low line resistance even after 450° C annealing for 300 min and exhibited 6 times longer electromigration (EM) lifetime compared with the previous Al-Si-Cu/CVD-W structure. This longer EM lifetime is also attributed to the suppression of WAl12 formation. This structure is one of the most promising interconnect structures for realizing sub-half-micron interconnects in future ULSIs.