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Proceedings Paper

The study of attenuated PSM structure for extreme ultraviolet lithography with minimized mask shadowing effect
Author(s): Chang Young Jeong; Byung Hun Kim; Tae Geun Kim; Sangsul Lee; Eun Jin Kim; Hye-Keun Oh; In-Sung Park; Jinho Ahn
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Paper Abstract

In this paper, we suggest an optimal attenuated phase shift mask (PSM) structure for extreme ultra violet lithography (EUVL) to minimize mask shadowing effect without loss of image contrast. The attenuated PSM proposed in this study is based on Fabry-Perot structure that consists of tantalum nitride (TaN) attenuator, Al2O3 spacer, and molybdenum (Mo) phase shifter. Deep ultra violet (DUV) reflectivity can be lowered down to 5% at 257nm for higher efficiency in DUV inspection process through the optimal thickness combination of TaN and Al2O3. Since the thickness variation of Mo dose not affect the DUV reflectivity, the phase shift effect can be controlled by Mo thickness only. As a result, attenuated PSM with phase shift of 180±6° and absorber reflectivity of 9.5% could be obtained. The total thickness of absorber stack is only 52nm. The analysis of aerial image was performed using SOLID-EUV simulation tool. The attenuated PSM showed steeper edge profile and higher image contrast compared to binary mask. Imaging properties including horizontal-vertical (H-V) critical dimension (CD) bias and pattern shift depending on both pattern size and process condition were compared to the binary mask using aerial image simulation. Attenuated PSM showed less H-V CD bias compared to that of binary mask. The 32nm dense pattern shows larger H-V CD bias than 45nm one due to larger shadowing of smaller pattern size. Especially, 32nm dense pattern at binary mask has very large H-V CD bias. The H-V CD bias was also affected by the change of focus. However, the H-V bias variation with defocus was below 1nm within the process latitude. We also obtained the result that the pattern shift is less sensitive than H-V CD bias with the optical property of absorber in EUVL.

Paper Details

Date Published: 21 March 2008
PDF: 8 pages
Proc. SPIE 6921, Emerging Lithographic Technologies XII, 69213Q (21 March 2008); doi: 10.1117/12.772533
Show Author Affiliations
Chang Young Jeong, Hanyang Univ. (South Korea)
Byung Hun Kim, Hanyang Univ. (South Korea)
Tae Geun Kim, Hanyang Univ. (South Korea)
Sangsul Lee, Hanyang Univ. (South Korea)
Eun Jin Kim, Hanyang Univ. (South Korea)
Hye-Keun Oh, Hanyang Univ. (South Korea)
In-Sung Park, Hanyang Univ. (South Korea)
Jinho Ahn, Hanyang Univ. (South Korea)

Published in SPIE Proceedings Vol. 6921:
Emerging Lithographic Technologies XII
Frank M. Schellenberg, Editor(s)

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