Diffractive phase element for shrinking focal spot diameter: Design, fabrication, and application to laser beam lithography |
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| Authors: | Yusuke Ogura Jun Tanida Yoshiki Ichioka Yoshiaki Mokuno Katsunori Matsuoka |
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| Affiliation: | (1) Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2–1, Yamadaoka, 565-0871 Suita, Osaka, Japan;(2) Nara National College of Technology, 22 Yata- cho, 639- 1080 Yamatokoriyama, Nara, Japan;(3) Osaka National Research Institute, 1- 8- 31 Midorigaoka, 563- 8577 Ikeda, Osaka, Japan;(4) Present address: National Institute of Advanced Industrial Science and Technology, Japan |
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| Abstract: | A diffractive phase element (DPE) capable of shrinking the main-lobe of the focal spot of an incident beam has been developed. The DPE is expected to be used in laser beam lithography to improve the resolution. Special constraints, which force the focal spot to be small while permitting increase of the side-lobes, are introduced in the design of the DPE using an iterative method based on the Gerchberg-Saxton algorithm. Two kinds of DPEs are fabricated by a laser beam lithography system of our own composition and their performances are experimentally measured. The minimum line width obtained by the system is improved from 1.2 μm to 1.0 μm with the fabricated DPE. Focal depth of the focusing system is discussed. |
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| Keywords: | diffractive phase element laser beam lithography focusing system spot diameter focal depth |
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