Etch modeling for model-based optical proximity correction for 65 nm node

With the continuous reduction of layout dimension, critical dimension control becomes more and more tricky. Being one contribution of critical dimension variation, etch bias correction needs to get more accurate. The correction by rule-based optical proximity correction, which only takes into account the distance to the facing outer and inner edges, is reaching its limit at 65 nm node. Indeed, its found to be not accurate enough in some particular configurations. Thus, applying etch correction by model-based optical proximity correction looks like a good solution. The etch bias to correct for can be approximated by a function of the local density, obtained by convoluting the design with Kernels. However, it is found to be still not accurate enough in some configurations if the Kernels used for etch modeling are symmetrical, as for optical part. In this study, several etch models are tested to correct etch bias variations of poly layer patterning for 65 nm node.