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Journal of Micro/Nanolithography, MEMS, and MOEMS • new

High-numerical aperture extreme ultraviolet scanner for 8-nm lithography and beyond
Author(s): Jan van Schoot; Eelco van Setten; Gijsbert Rispens; Kars Z. Troost; Bernhard Kneer; Sascha Migura; Jens Timo Neumann; Winfried Kaiser
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Paper 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.

Paper Details

Date Published: 30 October 2017
PDF: 16 pages
J. Micro/Nanolith. MEMS MOEMS 16(4) 041010 doi: 10.1117/1.JMM.16.4.041010
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 16, Issue 4
Show Author Affiliations
Jan van Schoot, ASML Netherlands B.V. (The Netherlands)
Eelco van Setten, ASML Netherlands B.V. (The Netherlands)
Gijsbert Rispens, ASML Netherlands B.V. (Netherlands)
Kars Z. Troost, ASML Netherlands B.V. (The Netherlands)
Bernhard Kneer, Carl Zeiss SMT GmbH (Germany)
Sascha Migura, Carl Zeiss SMT GmbH (Germany)
Jens Timo Neumann, Carl Zeiss SMT GmbH (Germany)
Winfried Kaiser, Carl Zeiss SMT GmbH (Germany)

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