Aberration measurement from specific photolithographic images: a different approach.
Techniques for measurement of higher-order aberrations of a projection optical system in photolithographic exposure tools have been established. Even-type and odd-type aberrations are independently obtained from printed grating patterns on a wafer by three-beam interference under highly coherent illumination. Even-type aberrations, i.e., spherical aberration and astigmatism, are derived from the best focus positions of vertical, horizontal, and oblique grating patterns by an optical microscope. Odd-type aberrations, i.e., coma and three-foil, are obtained by detection of relative shifts of a fine grating pattern to a large pattern by an overlay inspection tool. Quantitative diagnosis of lens aberrations with a krypton fluoride (KrF) excimer laser scanner is demonstrated.
Nomura
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Microelectronics Engineering Laboratory, Semiconductor Company, Toshiba Corporation, 8, Shinsugita-cho, Isogo-ku, Yokohama 235-8522, Japan.
Tawarayama
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Kohno
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