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High volume manufacturing of semiconductors using extreme ultraviolet lithography (EUVL) is off to a good start, and development of high-NA EUVL tool has started; however, EUV mask pattern inspection, one key technology supporting EUVL, is still not ready in terms of fully satisfying customers' major requirements, such as 1) defect sensitivity, 2) throughput, and 3) cost of ownership (CoO). There are three tool candidates that have the potential of meeting these requirements: optical inspection, actinic inspection, and e-beam inspection. The resolution of the optical inspection tool has almost reached its limit. The actinic inspection tool satisfies both defect sensitivity and throughput requirements, but the cost is high and it needs to support D2DB inspection capability. The e-beam tool has high resolution and sensitivity, but its low throughput which is a key issue. With this background, NuFlare has optimized its multi e-beam optics system to inspect EUV masks, and has made progress in verifying a POC tool as well as develop new image processing technology. From these verifications, the development has moved on to the feasibility study of inspecting EUV mask pattern defects with D2D and D2DB for the 5nm node and beyond. In this paper, we will present our technology for EUV mask inspection as well as our latest results.
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