Technical demand for the photomask is becoming severer along with super-miniaturization of the semiconductor patterns as shown in the ITRS roadmap. Defect inspection is especially becoming more challenging and difficult as the photomask design rules continue to shrink toward hp65-45nm and below. One of the factors for such difficulties is aggressive OPC (Optical Proximity Correction), which makes defect inspection extremely difficult. In lithography, ArF immersion lithography will be predominantly used as one of the powerful candidates for the technology for hp65-45nm. Therefore, we have to assure zero printable defects assuming the use of ArF immersion lithography. Recently, there is another issue of increase in mask production cost, causing QCD balance to start to collapse. To cope with this new problem, tool operation is being considered for inspections ranging from accelerating inspection in R&D phase to reasonable inspection in production phase. In this paper, inspection concept for operation of inspection tools in R&D and production phases is discussed, with special focus on the aerial image based inspection.
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