EUV patterning using CAR or MOX photoresist at low dose exposure for sub 36nm pitch

The semiconductor industry has been pushing the limits of scalability by combining 193nm immersion lithography with multi-patterning techniques for several years. Those integrations have been declined in a wide variety of options to lower their cost but retain their inherent variability and process complexity. EUV lithography offers a much desired path that allows for direct print of line and space at 36nm pitch and below and effectively addresses issues like cycle time, intra-level overlay and mask count costs associated with multi-patterning. However it also brings its own sets of challenges. One of the major barrier to high volume manufacturing implementation has been hitting the 250W power exposure required for adequate throughput [1]. Enabling patterning using a lower dose resist could help move us closer to the HVM throughput targets assuming required performance for roughness and pattern transfer can be met. As plasma etching is known to reduce line edge roughness on 193nm lithography printed features [2], we investigate in this paper the level of roughness that can be achieved on EUV photoresist exposed at a lower dose through etch process optimization into a typical back end of line film stack. We will study 16nm lines printed at 32 and 34nm pitch. MOX and CAR photoresist performance will be compared. We will review step by step etch chemistry development to reach adequate selectivity and roughness reduction to successfully pattern the target layer.