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Proceedings Paper

When calibration is not enough
Author(s): Jeffrey R. Kingsley; Leslie Johnson
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Paper Abstract

When added CD (Critical Dimension) capacity is needed there are several routes that can be taken -- add shifts and people to existing equipment, obtain additional equipment and staff or use an outside service provider for peak and emergency work. In all but the first scenario the qualification of the 'new' equipment, and correlation to the existing measurements, is key to meaningful results. In many cases simply calibrating the new tool with the same reference material or standard used to calibrate the existing tools will provide the level of agreement required. In fact, calibrating instruments using different standards can provide an acceptable level of agreement in cases where accuracy is a second tier consideration. However, there are also situations where factors outside of calibration can influence the results. In this study CD measurements from a mask sample being used to qualify an outside service provider showed good agreement for the narrower linewidths, but significant deviation occurred with increasing CD. In the course of a root cause investigation, it was found that there are a variety of factors that may influence the agreement found between two tools. What are these 'other factors' and how are they found? In the present case the results of a 'round robin' consensus from a variety of tools was used to initially determine which tool needed to be investigated. The instrument parameters felt to be the most important causes of the disagreement were identified and experiments run to test their influence. The factors investigated as the cause of the disagreement included (1) Type of detector and location with respect to sample, (2) Beam Voltage, (3) Scan Rotation/Sample Orientation issues and (4) Edge Detection Algorithm.

Paper Details

Date Published: 30 December 1999
PDF: 9 pages
Proc. SPIE 3873, 19th Annual Symposium on Photomask Technology, (30 December 1999); doi: 10.1117/12.373366
Show Author Affiliations
Jeffrey R. Kingsley, Charles Evans & Associates (United States)
Leslie Johnson, Etec Systems, Inc. (United States)

Published in SPIE Proceedings Vol. 3873:
19th Annual Symposium on Photomask Technology
Frank E. Abboud; Brian J. Grenon, Editor(s)

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