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Proceedings Paper

Study of pupil filters for depth of focus enhancement in printing contact holes
Author(s): Chun-Ming Albert Wang; Shinn Sheng Yu; Anthony Yen
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Paper Abstract

In this paper, we investigate depth of focus (DOF) improvement using radially symmetric pure phase pupil filters. Optimization of such filters starts by requiring their corresponding point spread function be flat in the axial direction. it is found that DOF for 0.18micrometers contact holes using an optimized filter is about 1micrometers , while printing them without filters is hardly feasible, using a binary mask. however, this filter introduces 2/3 intensity loss and therefore affects the processing throughput. We also apply the optimized filter to the imaging of 0.15micrometers contact holes and 0.18micrometers lines and spaces. For 0.15micrometers contact holes, it still performs better than other case, but normalized image log-slopes are low for all cases. From the simulation data of 0.18micrometers lines and spaces, pure phase filters may not be good candidates for improving their DOF. Other DOF enhancing techniques such as quadrupole illumination may be required.

Paper Details

Date Published: 26 July 1999
PDF: 9 pages
Proc. SPIE 3679, Optical Microlithography XII, (26 July 1999);
Show Author Affiliations
Chun-Ming Albert Wang, Taiwan Semiconductor Manufacturing Co. (Taiwan)
Shinn Sheng Yu, Taiwan Semiconductor Manufacturing Co. (Taiwan)
Anthony Yen, Taiwan Semiconductor Manufacturing Co. (United States)

Published in SPIE Proceedings Vol. 3679:
Optical Microlithography XII
Luc Van den Hove, Editor(s)

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