Extreme ultraviolet lithography reticle local CD uniformity correlation to wafer local CD uniformity

Adam Lyons; Tom Wallow; Dong-Seok Nam; Gisung Yoon; Baorui Yang; Mike Hermes

doi:10.1117/12.2643523

1 December 2022 Extreme ultraviolet lithography reticle local CD uniformity correlation to wafer local CD uniformity

Adam Lyons, Tom Wallow, Dong-Seok Nam, Gisung Yoon, Baorui Yang, Mike Hermes

Proceedings Volume 12293, Photomask Technology 2022; 122930M (2022) https://doi.org/10.1117/12.2643523
Event: SPIE Photomask Technology + EUV Lithography, 2022, Monterey, California, United States

Abstract

In this contribution we describe an experimental study measuring local CD uniformity (LCDU) of DRAM contact arrays on both an EUV reticle and corresponding exposed wafer. Direct measurement of LCDU from reticle SEM images is compared to the reticle component of wafer level LCDU determined by decomposition of wafer level only data. The goal of this study is to better understand the contribution of reticle LCDU to wafer LCDU and the degree of accuracy to which the reticle component can be determined without reticle metrology. In addition to comparing the two methods of determining mask LCDU we use the measured mask contours as input to ASML Tachyon lithography simulation software and compare the simulated and experimental wafer CDs, CD distributions, and local MEEF. This gives some insight on the proportion of the mask variability coming from the variation of absorber edge placement. Three different DRAM contact array pitches are examined 36, 38 and 40nm. Each array contains a registration mark to allow each individual contact to be reliably identified. Reticle SEM images are collected for 20 locations for each pitch and the three highest and three lowest LCDU locations are selected. These six selected reticle locations (per pitch) are measured by SEM in resist at 117 die across a CDU wafer (i.e. a wafer where all die have the same focus and exposure dose). Each wafer location is measured twice. With this dataset the reticle and wafer LCDU, CD and placement can all be measured and correlated, and the reticle, metrology and stochastic components of the wafer LCDU can be determined. Metrology is performed using ASML Brion’s MXP to extract contours from both the reticle and wafer SEM images.

Conference Presentation

Citation Download Citation

Adam Lyons, Tom Wallow, Dong-Seok Nam, Gisung Yoon, Baorui Yang, and Mike Hermes "Extreme ultraviolet lithography reticle local CD uniformity correlation to wafer local CD uniformity", Proc. SPIE 12293, Photomask Technology 2022, 122930M (1 December 2022); https://doi.org/10.1117/12.2643523

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