22 April 2011 The coherent EUV scatterometry microscope for actinic mask inspection and metrology
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Proceedings Volume 8081, Photomask and Next-Generation Lithography Mask Technology XVIII; 80810K (2011) https://doi.org/10.1117/12.896576
Event: Photomask and NGL Mask Technology XVIII, 2011, Yokohama, Japan
Abstract
For actinic mask inspection and metrology, we have developed a coherent EUV scatterometry microscope (CSM) at NewSUBARU of a synchrotron radiation facility. The CSM is composed of φ5-mm pinhole, turning and focusing multilayer mirrors, a test EUV mask and a back-illuminated CCD camera. Thus this system is lens-less system, records diffraction EUV light from a mask pattern, which is exposed with coherent EUV light. The CSM inspects defect on the EUV mask by the coherent-diffraction-imaging method. Aerial images of periodic and aperiodic patterns on the EUV mask were well reconstructed by the iterative calculation. Since the CSM data include only the diffraction intensity, the missing phase information is reconstructed. A defect with 10-nm width was well inspected. The CSM also evaluates critical dimension (CD) of the mask patterns by diffraction intensities. The mask is illuminated with six-degree angle of the incidence, which equals to the EUV lithography scanners. The test EUV mask of 6025 glass substrate has line-and-space (L/S) patterns of 22-nm nodes. Absorber thickness is about 70 nm. The CSM result is well corresponding with the CD-SEM result at whole mask area. And, high repeatability of 0.3 nm (3φ) is achieved.
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Tetsuo Harada, Masato Nakasuji, Teruhiko Kimura, Yutaka Nagata, Takeo Watanabe, Hiroo Kinoshita, "The coherent EUV scatterometry microscope for actinic mask inspection and metrology", Proc. SPIE 8081, Photomask and Next-Generation Lithography Mask Technology XVIII, 80810K (22 April 2011); doi: 10.1117/12.896576; https://doi.org/10.1117/12.896576
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