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6 May 2005 High-precision optical heterodyne interferometric dilatometer for determining absolute CTE of EUVL materials
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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.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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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