22 March 2010 Development of an ultrasonic system for super-precise measurement of zero-CTE temperature of EUVL-grade TiO2-SiO2 ultra-low-expansion glasses
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Abstract
This paper presents the development of a practical system for super-precise evaluation of zero-CTE temperatures T(zero- CTE) of TiO2-SiO2 glasses for extreme ultraviolet lithography (EUVL) by measuring leaky surface-acoustic-wave (LSAW) velocity VLSAW with a line-focus-beam ultrasonic material characterization (LFB-UMC) system. This new system can evaluate T(zero-CTE) from 20 to 150°C on the surfaces of glass substrates for photomasks and optical mirrors located at different positions in EUVL systems. This system operates in a stabilized temperature measurement environment (e.g., 23.00°C). It was demonstrated at 225 MHz for homogenized TiO2-SiO2 glass specimens with different annealing temperatures and realized an extremely homogeneous glass ingot with a ΔT(zero-CTE) of 1.6°C around 23.2°C. This ultrasonic system enables both glass manufacturers and users to speedily inspect all glass substrates with reliable data of T(zero-CTE).
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Jun-ichi Kushibiki, Jun-ichi Kushibiki, Mototaka Arakawa, Mototaka Arakawa, Yuji Ohashi, Yuji Ohashi, Toshio Sannomiya, Toshio Sannomiya, Yuko Maruyama, Yuko Maruyama, } "Development of an ultrasonic system for super-precise measurement of zero-CTE temperature of EUVL-grade TiO2-SiO2 ultra-low-expansion glasses", Proc. SPIE 7636, Extreme Ultraviolet (EUV) Lithography, 76362M (22 March 2010); doi: 10.1117/12.846570; https://doi.org/10.1117/12.846570
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