Resist Process Window Characterization for the 45-nm Node Using an Interferometric Immersion microstepper
Projection and interference imaging modalities for application to IC microlithography were compared at the 90 nm imaging node. The basis for comparison included simulated two-dimensional image in resist, simulated resist linesize, as well as experimental resist linesize response through a wide range of dose and focus values. Using resist CD as the main response (both in simulation and experimental comparisons), the two imaging modes were found nearly equivalent, as long as a suitable Focus-Modulation conversion is used. A Focus-Modulation lookup table was generated for the 45 nm imaging node, and experimental resist response was measured using an interferometric tool. A process window was constructed to match a hypothetical projection tool, with an estimated error of prediction of 0.6 nm. A demodulated interferometric imaging technique was determined to be a viable method for experimental measurement of process window data. As long as accurate assumptions can be made about the optical performance of such projection tools, the response of photoresist to the delivered image can be studied experimentally using the demodulated interferometric imaging approach.
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Anatoly Bourov, Stewart A Robertson, Bruce W. Smith, Michael A. Slocum, Emil C. Piscani, "Resist process window characterization for the 45-nm node using an interferometric immersion microstepper", Proc. SPIE 6153, Advances in Resist Technology and Processing XXIII, 61530R (29 March 2006); doi: 10.1117/12.657578; https://doi.org/10.1117/12.657578
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