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Proceedings Paper

Scatterometry measurements for process monitoring of polysilicon gate etch
Author(s): Scott Bushman; Steve Farrer
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Paper Abstract

This paper presents results from a prototype scatterometer which show that distinctly different zeroth-order diffraction signatures are produced for wafers processed under different etch conditions. We present comparisons between the profiles estimated using the scatterometer signatures and those measured using atomic force microscopy, in-line scanning electron microscopy, and cross-sectional scanning electron microscopy. We found that all the metrology techniques investigated provided useful information about the profile characteristics, but only the atomic force microscope and the scatterometer are suitable as in-line measurements of critical dimension profiles -- and only scatterometry provides estimates of the underlying film structure. In this study, the wafers consisted of patterned photoresist over blanket layers of a deep-ultravoilet anti-reflection coating, polysilicon, and silicon dioxide. These wafers were intentionally varied at the lithography step and intentionally misprocessed at the gate etch step to produce a wide range of process variation. Scatterometry measurements were made on multiple dies per wafer and estimates of feature profile information such as film thickness and critical dimension were generated by comparing the experimental signature to a library of theoretical solutions. We found that the scatterometer was capable of showing signal differences for different wafer processing conditions, and can be used as an in-line measurement of profile characteristics suitable for closed- loop process control of lithographic and etch processes.

Paper Details

Date Published: 25 August 1997
PDF: 12 pages
Proc. SPIE 3213, Process, Equipment, and Materials Control in Integrated Circuit Manufacturing III, (25 August 1997); doi: 10.1117/12.284624
Show Author Affiliations
Scott Bushman, Texas Instruments Inc. (United States)
Steve Farrer, Bio-Rad Labs. (United States)

Published in SPIE Proceedings Vol. 3213:
Process, Equipment, and Materials Control in Integrated Circuit Manufacturing III
Abe Ghanbari; Anthony J. Toprac, Editor(s)

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