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Proceedings Paper

Development of a captured image simulator for the differential interference contrast microscopes aiming to design 199 nm mask inspection tools
Author(s): Masataka Shiratsuchi; Yoshinori Honguh; Ryoichi Hirano D.D.S.; Riki Ogawa; Masatoshi Hirono; Takehiko Nomura
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Paper Abstract

Recently, technologies of ArF laser exposure tools and alternating phase shifting masks (Alt-PSM) are expected to be used in actual production. To utilize such newly developed technologies, it is inevitable to develop a mask inspection technology to check them properly. But it is currently difficult to check them precisely because sufficient image contrast is hard to obtain with any conventional mask inspection tools. Among many observation methods, the differential interference contrast (DIC) is one of a few methods that can be used to observe a differentiated phase shift of transmitted light of an object with high resolution. To study precisely the performance of this optical configuration, we built a new captured image simulator in which Wollaston prisms were modeled as a kind of phase modulation plates. We built this simulator as an extension of the captured image simulator we reported formerly), which is based on Rigorous Coupled- Wave Analysis (RCWA) to calculate diffractions; this enables us to properly treat effects of polarization, high NA, and 3-dimensional mask structures. We applied this simulator to see sensitivities of DIC against bumps and divots with various sizes. We found that the image contrast for small phase defects 20 to 50 nm in sizes is much higher in DIC microscopes than in conventional optical setup with coherence factor less than 1. We also found the dependence of captured images on polarizations and optical axis directions. We expect our simulator to be a useful tool for studying, designing, and developing mask inspection tools.

Paper Details

Date Published: 1 November 2007
PDF: 11 pages
Proc. SPIE 6730, Photomask Technology 2007, 67304W (1 November 2007); doi: 10.1117/12.747909
Show Author Affiliations
Masataka Shiratsuchi, Toshiba Corp. (Japan)
Yoshinori Honguh, Toshiba Corp. (Japan)
Ryoichi Hirano D.D.S., Advanced Mask Inspection Technology (Japan)
Riki Ogawa, Advanced Mask Inspection Technology (Japan)
Masatoshi Hirono, Advanced Mask Inspection Technology (Japan)
Takehiko Nomura, NuFlare Technology, Inc. (Japan)

Published in SPIE Proceedings Vol. 6730:
Photomask Technology 2007
Robert J. Naber; Hiroichi Kawahira, Editor(s)

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