Tool-to-tool optical proximity effect matching

IC manufacturers have a strong demand for transferring a working process from one scanner to another. In an ideal transfer, a reticle set that produces devices within specification on a certain scanner has the same performance on another exposure tool. In real life, however, reticles employ optical proximity correction (OPC) which incorporates by definition the inherent optical fingerprint of a specific exposure tool and process. In order to avoid the additional cost of developing a new OPC model and acquiring a new reticle for each exposure tool, IC manufacturers therefore wish to "match" the optical fingerprint of their scanners as closely as possible. In this paper, we report on the matching strategy that we developed to perform a tool-to-tool matching. We present experimental matching results for several tool combinations at numerical apertures (NA) 0.75, 0.85 and 1.2. Matching of two exposure tools is obtained by determining the sensitivities to scanner parameter variations like NA, Sigma, Focus Drilling, Ellipticity and Dose from wafer data and/or simulations. These sensitivities are used to calculate the optimal scanner parameters for matching the two tools.