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Proceedings Paper

Diffraction Characterization For Process Monitoring, Linewidth Measurement And Alignment
Author(s): H S Damar; F P Chan; TT. Albert Wu; A R. Neureuther
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Paper Abstract

An automated He-Ne laser spectrometer is used to explore fundamental issues associated with non-destructive IC process monitoring on diffraction from drop-in test sites. The system is also used to explore how diffraction alignment signals are affected by incidence angle variations and resist coating. The apparatus consists of an x-ray spectrometer stage which has been retrofit with a He-Ne laser system. The system is automated through the use of an IBM-PC with stepping motor controllers and an auto-ranging current to voltage converter. The diffraction from 3.0µm period features on a specially fabricated wafer consist-ing entirely of drop-in test sites is characterized and correlated with other optical and SEM measurements. Site-to-site correlations across the wafer in various directions show a very significant "bull's eye" effect especially beyond a 3 cm radius. A similar sensitivity is not seen in either image-shearing or line-edge-scanning optical measure-ments. Theoretically, a physical optics model for the diffraction from the structure is shown to be too approximate to predict the measured site-to-site diffraction signals. To explore issues associated with diffraction based alignment, such as might occur with zone plate alignment signals, the first order diffraction is studied as a function of incidence angle and resist coating thickness. The incidence angle did not show rapid variations which might be expected while resist thickness changes gave very significant signal level fluctuations.

Paper Details

Date Published: 29 June 1984
PDF: 7 pages
Proc. SPIE 0470, Optical Microlithography III: Technology for the Next Decade, (29 June 1984); doi: 10.1117/12.941907
Show Author Affiliations
H S Damar, University of California (United States)
F P Chan, University of California (United States)
TT. Albert Wu, University of California (United States)
A R. Neureuther, University of California (United States)

Published in SPIE Proceedings Vol. 0470:
Optical Microlithography III: Technology for the Next Decade
Harry L. Stover, Editor(s)

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