Proximity dummy feature placement and selective via sizing for process uniformity in a trench-first-via-last dual-inlaid metal process

In a trench-first-via-last (TFVL) dual-inlaid metal process, the thickness of resist coated in the via definition step after trench formation varies according to underlying trench topography. Variation in resist thickness reduces via size uniformity and thus process window. Based on the modeling of resist thickness at a via location as a weighted sum of nearby trench densities, layout modifications of proximity dummy feature placement and selective via sizing are introduced to increase via size uniformity. Experimental results show significantly enlarged process window after proximity dummy features are inserted.