0.55NA EUV contact hole process optimization to enhance depth of focus

One of the most critical layers in DRAM production is comprised of large arrays of dense contact holes. With more advanced nodes, the pitch shrinkage of these contact holes results in a more significant contribution of the photoresist, its processing, and resulting stochastic effects to pattern quality and yield. This becomes even more critical for 0.55NA EUV use cases, where the reduced depth of focus decreases the usable process window. Optimized photoresist processing, including etch, is one of the enablers for driving down the stochastic variation for these patterns.