A chromatic aberration-free heterodyne alignment for optical lithography

This paper describes the principle of a new alignment method (SMART) and alignment optics using an optical-heterodyne technique. This SMART dose not need to correct chromatic aberration. Therefore, it dose not require any mechanism, such as mirrors, a prism or a lens system to correct chromatic aber...

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Bibliographic Details
Published inJapanese Journal of Applied Physics Vol. 29; no. 11; pp. 2568 - 2571
Main Authors HIGASHIKI, T, TOJO, T, TABATA, M, NISHIZAKA, T, MATSUMOTO, M, SAMEDA, Y
Format Journal Article
LanguageEnglish
Published Tokyo Japanese journal of applied physics 01.11.1990
Subjects
Exact sciences and technology
Fundamental areas of phenomenology (including applications)
Optical elements, devices, and systems
Optics
Physics
Characterization
Alignment
Heterodyne system
Lithography
Chromatic aberration
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Summary:This paper describes the principle of a new alignment method (SMART) and alignment optics using an optical-heterodyne technique. This SMART dose not need to correct chromatic aberration. Therefore, it dose not require any mechanism, such as mirrors, a prism or a lens system to correct chromatic aberration for the projection lens. A pair of one-dimensional gratings for the mask mark and a checker grating for the wafer mark were used in SMART optics. The relation displacement between the mask and the wafer can be directly detected by measuring the phase difference of the heterodyne beat signals. The experimental result for the phase difference was similar to the calculation result. An alignment signal variation of less than 10 nm was obtained.
ISSN:0021-4922
1347-4065
DOI:10.1143/jjap.29.2568