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A statistical approach to quality control of non-normal lithographical overlay distributions

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4 Author(s)
R. M. Booth ; IBM Technology Products, Route 52, East Fishkill faciliy, Hopewell Junction, New York 12533, USA ; K. A. Tallman ; T. J. Wiltshire ; P. L. Yee

To achieve the high reliability and performance required by integrated circuit (IC) chips in IBM Enterprise System/9000™ processors, lithography tool centerline overlay variations between masking levels were specified at ± 0.3% µm and circuit design images were transferred with 5× step-and-repeat photolithography tools. In contrast to data obtained from 1× lithography tools, the level-to-level overlay data which characterize deviations from circuit design rules did not fit a normal distribution, and quality control was not achieved with traditional statistical procedures. A methodology was empirically developed which transformed measured data into worst-case overlay points and approximated the data by a gamma distribution. More than 80% of the worst-case distributions were fit by the gamma distribution. The transformation of chip worst-case overlay data and the quality control testing applicable to 5× step-and-repeat lithography tool processes are described in this paper.

Note: The Institute of Electrical and Electronics Engineers, Incorporated is distributing this Article with permission of the International Business Machines Corporation (IBM) who is the exclusive owner. The recipient of this Article may not assign, sublicense, lease, rent or otherwise transfer, reproduce, prepare derivative works, publicly display or perform, or distribute the Article.  

Published in:

IBM Journal of Research and Development  (Volume:36 ,  Issue: 5 )