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Proceedings Paper

The Application Of Coherence Probe Microscopy For Submicron Critical Dimension Linewidth Measurement
Author(s): J. William Dockrey; Douglas Hendricks
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Paper Abstract

The present trend in submicron critical dimension process control is toward in-line SEM systems. Recently several new optical tools have been developed for application in the submicron environment. Optical metrology offers many well publicized operational advantages and in general higher throughput than an SEM. This paper reports on the application of a new optical metrology technique based on coherence probe imaging using a Linnik interferometer with incoherent, broad band illumination. Linewidth measurement is performed on three dimensional images produced by determining the degree of mutual coherence in the reference and object planes of the interferometer. The mutual coherence function is evaluated on a pixel by pixel basis as the sample is moved in the z direction. A commonly encountered problem of coherent optical metrology arises from interference produced by the interaction of the coherent light wave with material of varying optical path length. Incoherent systems offer a higher degree of immunity to material induced phase interference but suffer from poor resolution. The use of coherence probe imaging increases the resolution while preserving the positive aspects of incoherent illumination. The ability of the coherence probe microscope to perform accurate edge detection in a submicron IC fabrication process subject to a wide degree of process variance is compared with the in-line SEM. The effect of material thin film variations have been evaluated with respect to their influence on measurement accuracy and precision. Response surface models are described which illustrate the effect of thin film material factors on coherence probe measurement accuracy and precision. These factors include relative film reflectance, thin film thickness, and feature line width. The effects of resist slope variations and proximity of measured feature to other features is also evaluated. Measurement precision has been evaluated using component variance analysis to isolate the sources of measurement error relative to a 0.3 μm process tolerance.

Paper Details

Date Published: 19 July 1989
PDF: 18 pages
Proc. SPIE 1087, Integrated Circuit Metrology, Inspection, and Process Control III, (19 July 1989); doi: 10.1117/12.953086
Show Author Affiliations
J. William Dockrey, Motorola Inc. (United States)
Douglas Hendricks, KLA Instruments Corp. (United States)

Published in SPIE Proceedings Vol. 1087:
Integrated Circuit Metrology, Inspection, and Process Control III
Kevin M. Monahan, Editor(s)

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