17 April 2014 Spectral purity enhancement for the EUV lithography systems by suppressing UV reflection from multilayers
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Abstract
Plasma based radiation sources optimized to emit 13.5 nm Extreme UV radiation also produce a significant amount of light at longer wavelengths. This so called out-of-band (OoB) radiation is detrimental for the imaging capabilities of an EUV lithographic imaging system, particularly the ultraviolet (UV) parts of the light (λ=100-400 nm). To suppress these wavelengths while maintaining the high efficiency of the mirror for EUV light, several methods have been developed, including phase-shift gratings (PsG) and anti-reflection layers (SPE layer). Both methods have achieved a suppression factor of 10 - 30 around the target wavelength. To achieve a full band suppression effect with a minimum loss of EUV light, a new scheme based on surface pyramid structures was developed. An average suppression of more than 10 times was achieved with a relative EUV efficiency of 82.2% by using the Si pyramids structure (compared to a flat multilayer (ML)). Recently, we have successfully produced a pyramid structure consisting of multilayers which greatly improves the relative EUV efficiency to 94.2%.
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Qiushi Huang, Meint de Boer, Jonathan Barreaux, Daniel Mathijs Paardekooper, Toine van den Boogaard, Robbert van de Kruijs, Erwin Zoethout, Eric Louis, Fred Bijkerk, "Spectral purity enhancement for the EUV lithography systems by suppressing UV reflection from multilayers", Proc. SPIE 9048, Extreme Ultraviolet (EUV) Lithography V, 90480G (17 April 2014); doi: 10.1117/12.2046415; https://doi.org/10.1117/12.2046415
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