High-precision optical heterodyne interferometric dilatometer for determining absolute CTE of EUVL materials

Yoshimasa Takeichi; Iwao Nishiyama; Naofumi Yamada

doi:10.1117/12.599400

6 May 2005 High-precision optical heterodyne interferometric dilatometer for determining absolute CTE of EUVL materials

Yoshimasa Takeichi, Iwao Nishiyama, Naofumi Yamada

Proceedings Volume 5751, Emerging Lithographic Technologies IX; (2005) https://doi.org/10.1117/12.599400
Event: Microlithography 2005, 2005, San Jose, California, United States

Abstract

The low-thermal-expansion materials (LTEMs) used in extreme ultraviolet lithography (EUVL) must have an ultralow coefficient of thermal expansion (CTE) on the order of 10^-9 K^-1. Unfortunately, the resolution of commercial dilatometers is too low to accurately measure the properties of LTEMs for EUVL. So, we have developed a practical dilatometer tailored to meet EUVL requirements. It is based on the double-path heterodyne interferometer technology developed by AIST. This technology has the advantage of providing absolute CTE measurements, which means direct measurement of the change in specimen length with an interferometer. The design of the dilatometer has been optimized to yield high-precision measurements, and it should enable displacement measurements to be made with a resolution of better than one nanometer.

Citation Download Citation

Yoshimasa Takeichi, Iwao Nishiyama, and Naofumi Yamada "High-precision optical heterodyne interferometric dilatometer for determining absolute CTE of EUVL materials", Proc. SPIE 5751, Emerging Lithographic Technologies IX, (6 May 2005); https://doi.org/10.1117/12.599400

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