30 October 2017 High-numerical aperture extreme ultraviolet scanner for 8-nm lithography and beyond
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Abstract
Current extreme ultraviolet (EUV) projection lithography systems exploit a projection lens with a numerical aperture (NA) of 0.33. It is expected that these will be used in mass production in the 2018/2019 timeframe. By then, the most difficult layers at the 7-nm logic and the mid-10-nm DRAM nodes will be exposed. These systems are a more economical alternative to multiple-exposure by 193 argon fluoride immersion scanners. To enable cost-effective shrink by EUV lithography down to 8-nm half pitch, a considerably larger NA is needed. As a result of the increased NA, the incidence angles of the light rays at the mask increase significantly. Consequently, the shadowing and the variation of the multilayer reflectivity deteriorate the aerial image contrast to unacceptably low values at the current 4 × magnification. The only solution to reduce the angular range at the mask is to increase the magnification. Simulations show that the magnification has to be doubled to 8 × to overcome the shadowing effects. Assuming that the mask infrastructure will not change the mask form factor, this would inevitably lead to a field size that is a quarter of the field size of the current 0.33-NA step and scan systems and reduce the throughput (TPT) of the high-NA scanner to a value below 100 wafers per hour unless additional measures are taken. This paper presents an anamorphic step and scan system capable of printing fields that are half the field size of the current full field. The anamorphic system has the potential to achieve a TPT in excess of 150 wafers per hour by increasing the transmission of the optics, as well as increasing the acceleration of the wafer stage and mask stage. This makes it an economically viable lithography solution.
© 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
Jan van Schoot, Eelco van Setten, Gijsbert Rispens, Kars Z. Troost, Bernhard Kneer, Sascha Migura, Jens Timo Neumann, Winfried Kaiser, "High-numerical aperture extreme ultraviolet scanner for 8-nm lithography and beyond," Journal of Micro/Nanolithography, MEMS, and MOEMS 16(4), 041010 (30 October 2017). https://doi.org/10.1117/1.JMM.16.4.041010 . Submission: Received: 27 June 2017; Accepted: 26 September 2017
Received: 27 June 2017; Accepted: 26 September 2017; Published: 30 October 2017
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