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The study of attenuated PSM structure for extreme ultra violet lithography with minimized mask shadowing effect(

Title
The study of attenuated PSM structure for extreme ultra violet lithography with minimized mask shadowing effect(
Author
오혜근
Keywords
Aerial image; Attenuated PSM; EUVL; Horizontal-vertical CD bias; Shadowing effect
Issue Date
2008-02
Publisher
SPIE
Citation
Proceedings of SPIE - The International Society for Optical Engineering, v. 6921, Article no. 69213Q
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 to the optical property of absorber in EUVL.
URI
https://www.spiedigitallibrary.org/conference-proceedings-of-spie/6921/1/The-study-of-attenuated-PSM-structure-for-extreme-ultraviolet-lithography/10.1117/12.772533.fullhttp://repository.hanyang.ac.kr/handle/20.500.11754/76771
ISSN
0277-786X
DOI
10.1117/12.772533
Appears in Collections:
COLLEGE OF SCIENCE AND CONVERGENCE TECHNOLOGY[E](과학기술융합대학) > APPLIED PHYSICS(응용물리학과) > Articles
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