17 October 2008 Wafer plane inspection evaluated for photomask production
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Wafer Plane Inspection (WPI) is a novel approach to inspection, developed to enable high inspectability on fragmented mask features at the optimal defect sensitivity. It builds on well-established high resolution inspection capabilities to complement existing manufacturing methods. The production of defect-free photomasks is practical today only because of informed decisions on the impact of defects identified. The defect size, location and its measured printing impact can dictate that a mask is perfectly good for lithographic purposes. This inspection - verification - repair loop is timeconsuming and is predicated on the fact that detectable photomask defects do not always resolve or matter on wafer. This paper will introduce and evaluate an alternative approach that moves the mask inspection to the wafer plane. WPI uses a high NA inspection of the mask to construct a physical mask model. This mask model is used to create the mask image in the wafer plane. Finally, a threshold model is applied to enhance sensitivity to printing defects. WPI essentially eliminates the non-printing inspection stops and relaxes some of the pattern restrictions currently placed on incoming photomask designs. This paper outlines the WPI technology and explores its application to patterns and substrates representative of 32nm designs. The implications of deploying Wafer Plane Inspection will be discussed.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Emily Gallagher, Karen Badger, Mark Lawliss, Yutaka Kodera, Jaione Tirapu Azpiroz, Song Pang, Hongqin Zhang, Eugenia Eugenieva, Chris Clifford, Arosha Goonesekera, and Yibin Tian "Wafer plane inspection evaluated for photomask production", Proc. SPIE 7122, Photomask Technology 2008, 71221B (17 October 2008); doi: 10.1117/12.801945; https://doi.org/10.1117/12.801945

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