Full-chip curvilinear inverse lithography technology (ILT) requires mask writers to write full reticle curvilinear mask patterns in a reasonable write time. We jointly study and present the benefits of a full-chip, curvilinear, stitchless ILT with mask-wafer co-optimization (MWCO) for variable-shaped beam (VSB) mask writers and validate its benefits on mask and wafer at Micron Technology. The full-chip ILT technology employed, first demonstrated in a paper presented at the 2019 SPIE Photomask Technology Conference, produces curvilinear ILT mask patterns without stitching errors, and with process windows enlarged by over 100% compared to the OPC process of record, while the mask was written by multibeam mask writer. At the 2020 SPIE Advanced Lithography Conference, a method was introduced in which MWCO is performed during ILT optimization. This approach enables curvilinear ILT for 193i masks to be written on VSB mask writers within a practical, 12-h time frame, while also producing the largest process windows. We first review MWCO technology, then curvilinear ILT mask patterns written by VSB mask writer, and then show the corresponding 193i process wafer prints. Evaluations of mask write times and mask quality in terms of critical dimension uniformity and process windows are also presented. |
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Vestigial sideband modulation
Semiconducting wafers
Optical proximity correction
SRAF
Critical dimension metrology
Lithography
Printing