30 July 2002 0.33-k1 ArF lithography for 100-nm DRAM
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Abstract
We have evaluated 0.33k1 ArF lithography using 0.63NA scanner to develop 100 nm DRAM. ArF resist problems were resist pattern shrinkage during CD SEM measurement, resist pattern collapse during wet development and poor etch resistance. Off-Site Measurement (OSM) method has been developed for decreasing pattern shrinkage. With OSM method, 8nm of CD shrinkage was down to 2nm for 100nm L/S patterns. We have found a proper BARC material that prevents resist patterns falling down. Lack of etch resistance was compensated by hard mask. With W/SiN hard mask, acrylate- type resist patterns were transferred well into W/poly-Si gate patterns. We have simulated process window of critical DRAM cell patterns (isolation, gate, bit line contact, storage node) in the simple off-axis illumination (OAI) and optical proximity correction (OPC) conditions based on single exposure. Simulation results were verified by lithography tests and it turned out that 0.33k1 process was possible with exposure latitude of above 10% and focus latitude of more than 0.4 micrometers . 0.33k1 ArF lithography was successfully implemented into 100 nm DRAM with CD uniformity of 10nm (3 (sigma) ) and overlay accuracy of 30 nm (mean +3 (sigma) ). We have also evaluated double exposure technique using dipole illumination targeting 90 nm in order to see the possibility of 0.29k1 process. 0.29k1 process was also likely to be possible, although some specific improvements were recommended for the wider process window. From the simulation and resist patterning results, we believe that 0.85 NA lens will be able to extend ArF lithography into 75 nm by single exposure technology using crosspole illumination (0.33k1 process) and 65 nm by double exposure technology using dipole and crosspole illumination (0.29k1 process).
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Cheol-Kyu Bok, Cheol-Kyu Bok, Seok-Kyun Kim, Seok-Kyun Kim, Hee-Bom Kim, Hee-Bom Kim, Jin-Sung Oh, Jin-Sung Oh, Chang-Nam Ahn, Chang-Nam Ahn, Ki-Soo Shin, Ki-Soo Shin, } "0.33-k1 ArF lithography for 100-nm DRAM", Proc. SPIE 4691, Optical Microlithography XV, (30 July 2002); doi: 10.1117/12.474631; https://doi.org/10.1117/12.474631
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