16 March 2009 Scanner-dependent optical proximity effects
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Abstract
Optical imaging of IC critical designs is impacted by optical proximity effects, OPEs, originating from finite numerical aperture of projection lenses used in modern projectors. The OPE's are caused by filtering of pattern diffraction orders falling outside of the lens band pass. Controlling OPEs is so critical to IC performance, that IC design community implemented optical proximity correction, OPC, modifying the IC mask patterns to provide wafer images matching the IC design intent. The mainstream OPC uses optical models representing fundamental imaging setup and it does not capture the impacts of engineering scanner tool constraints. The OPEs are impacted by scanner lens and illuminator signatures causing CD excursions large in comparison to the CD error budgets(1). The magnitude of the scanner impacts on OPEs necessitated new optical modeling paradigm involving imaging models imbedding scanner signatures representing population of scanners of a given type. These scanner-type based models represent quantum leap in accuracy of lithography simulation technology, resulting in OPE and OPC representing a broad range of realistic scanner characteristics(2). In this context, a relevant question is: to what degree, the signatures of individual scanners impact the accuracy of imaging models and OPE predictions? To answer this question, we analyzed optical proximity responses of hyper-NA scanners represented by their signatures. We first studied a set of OPEs impacted by the scanner-type signatures. We then generated a set of corresponding OPEs impacted by the signatures of individual scanners. We compared the two kinds of OPEs and highlighted the scanner-specific image formation responses.
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Jacek K. Tyminski, Jacek K. Tyminski, Tomoyuki Matsuyama, Tomoyuki Matsuyama, Toshiharu Nakashima, Toshiharu Nakashima, Ryuichi Inoue, Ryuichi Inoue, } "Scanner-dependent optical proximity effects", Proc. SPIE 7274, Optical Microlithography XXII, 72740U (16 March 2009); doi: 10.1117/12.810850; https://doi.org/10.1117/12.810850
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