Electromigration reliability for a tungsten-filled via hole structure

Experiments have shown that the electromigration reliability for conventional nonfilled via holes decreases with via hole diameter reduction. Tungsten-filled via hole reliability, however, is independent of the via hole diameter and improves significantly compared with the nonfilled via hole structure. The electromigration failure mechanism for the tungsten-filled via hole structures was investigated by two-dimensional numerical simulation. Current crowding points were found near the via hole edge in the aluminum part. Via hole resistance change during the electromigration test was also evaluated. When aluminum-silicon was used for the metal lines, via hole resistance increased, due to the migration of silicon in the aluminum line. However, it was estimated as being negligibly small for unusual operating conditions.<
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