This paper presents a method taking into account the overlay variation and the Resist Image simulation across the process window variation to estimate the design sensitivity to overlay. Areas in the design are classified with specific metrics, from the highest to the lowest overlay sensitivity. This classification can be used to evaluate the robustness of a full chip product to process variability or to work with designers during the design library development. The ultimate goal is to evaluate critical structures in different contexts and report the most critical ones.
In this paper, we study layers interacting together, such as Contact/Poly area overlap or Contact/Active distance. ASML-Brion tooling allowed simulating the different resist contours and applying the overlay value to one of the layers. Lithography Manufacturability Check (LMC) detectors are then set to extract the desired values for analysis.
Two different approaches have been investigated. The first one is a systematic overlay where we apply the same overlay everywhere on the design. The second one is using a real overlay map which has been measured and applied to the LMC tools. The data are then post-processed and compared to the design target to create a classification and show the error distribution. Figure: