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Proceedings Paper

Effect of wafer geometry on lithography chucking processes
Author(s): Kevin T. Turner; Jaydeep K. Sinha
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Paper Abstract

Wafer flatness during exposure in lithography tools is critical and is becoming more important as feature sizes in devices shrink. While chucks are used to support and flatten the wafer during exposure, it is essential that wafer geometry be controlled as well. Thickness variations of the wafer and high-frequency wafer shape components can lead to poor flatness of the chucked wafer and ultimately patterning problems, such as defocus errors. The objective of this work is to understand how process-induced wafer geometry, resulting from deposited films with non-uniform stress, can lead to high-frequency wafer shape variations that prevent complete chucking in lithography scanners. In this paper, we discuss both the acceptable limits of wafer shape that permit complete chucking to be achieved, and how non-uniform residual stresses in films, either due to patterning or process non-uniformity, can induce high spatial frequency wafer shape components that prevent chucking. This paper describes mechanics models that relate non-uniform film stress to wafer shape and presents results for two example cases. The models and results can be used as a basis for establishing control strategies for managing process-induced wafer geometry in order to avoid wafer flatness-induced errors in lithography processes.

Paper Details

Date Published: 19 March 2015
PDF: 6 pages
Proc. SPIE 9424, Metrology, Inspection, and Process Control for Microlithography XXIX, 94240L (19 March 2015); doi: 10.1117/12.2085693
Show Author Affiliations
Kevin T. Turner, Univ. of Pennsylvania (United States)
Jaydeep K. Sinha, KLA-Tencor Corp. (United States)


Published in SPIE Proceedings Vol. 9424:
Metrology, Inspection, and Process Control for Microlithography XXIX
Jason P. Cain; Martha I. Sanchez, Editor(s)

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