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Proceedings Paper

Techniques For Optical Measurement Of Registration
Author(s): L. J. Zych; G. Spadini
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Paper Abstract

This paper discusses an optical technique capable of reliably measuring registration to few hundredths of a micron on virtually any layer. It has overcome the accuracy limitations and the proximity effect error present in other optical techniques. In spite of the recent popularity of highly accurate computerized electrical registration measurements optical registration measurements are still popular and necessary. This is because nonconductive layers, including resist, cannot be measured electrically. A quick optical technique with a high degree of accuracy has been developed and put to use. The measurement is made through a microscope, and a computer pattern recognition follows. It is free of the resolution limits inherent in such structures as optical verniers, which are bound to typically 0.1 microns by the grid size used to make the mask. This method employs a direct optical misalignment measurement between two matching structures and is capable of resolving 0.01 microns. It is also free of the proximity effects which make many verniers and pattern recognition schemes inaccurate. Proper microscope calibration, adjustments, and pattern recognition algorithms are key in making this technique work. The apertures must be accurately aligned and the focus properly adjusted to provide the right image. An HP 9000-226 computer has been custom interfaced to a Leitz microscope and a set of algorithms written. The result is a highly accurate, fast, and user friendly optical measurement system capable of measuring registration on all layers.

Paper Details

Date Published: 23 July 1985
PDF: 8 pages
Proc. SPIE 0538, Optical Microlithography IV, (23 July 1985); doi: 10.1117/12.947761
Show Author Affiliations
L. J. Zych, VLSI Technology Inc. (United States)
G. Spadini, VLSI Technology Inc. (United States)


Published in SPIE Proceedings Vol. 0538:
Optical Microlithography IV
Harry L. Stover, Editor(s)

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