Articles

Coherence control of illumination optics in mask inspection systems

[+] Author Affiliations
Akira Takada

Topcon Corporation, Corporate R&D Center, General Engineering and Quality Assurance Division, 75-1 Hasunuma-cho, Itabashi-ku, Tokyo 174-8580, Japan and Tokyo Polytechnic University, Faculty of Engineering, Department of Photonic Information and Media Engineering, 1583 Iiyama, Atsugi, Kanagawa 243-0297, Japan

Toru Tojo

Topcon Corporation, Corporate R&D Center, General Engineering and Quality Assurance Division, 75-1 Hasunuma-cho, Itabashi-ku, Tokyo 174-8580, Japan

Masato Shibuya

Tokyo Polytechnic University, Faculty of Engineering, Department of Photonic Information and Media Engineering, 1583 Iiyama, Atsugi, Kanagawa 243-0297, Japan

J. Micro/Nanolith. MEMS MOEMS. 7(4), 043010 (November 12, 2008). doi:10.1117/1.3013458
History: Received May 15, 2008; Revised July 22, 2008; Accepted August 05, 2008; Published November 12, 2008
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One annoying problem that degrades high-fidelity pattern images in mask-defect inspection systems is the generation of ghost images in the imaging process. Ghost images arise from spatial coherence periodicity on the mask plane, which is due to periodic and discrete arrangements of fly-eye elements in mask inspection optics. By considering the contrast of ghost images under partial coherence illumination, we can derive the condition that represents the necessary number of fly-eye elements to substantially suppress ghost images in the image field. In addition, we confirm this theoretically derived condition of suppressing ghost images by numerical calculations. As a result, we prove that this suppresing condition is effective, and that the nonuniformity in distribution of image intensity can also be reduced in this way.

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© 2008 Society of Photo-Optical Instrumentation Engineers

Citation

Akira Takada ; Toru Tojo and Masato Shibuya
"Coherence control of illumination optics in mask inspection systems", J. Micro/Nanolith. MEMS MOEMS. 7(4), 043010 (November 12, 2008). ; http://dx.doi.org/10.1117/1.3013458


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