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Proceedings Paper

Performance of a submicron litho process under CLSM metrology with linearity and discrimination measurements
Author(s): Mircea V. Dusa; Tony DiBiase; Harris J. Keston
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Paper Abstract

An attempt is made to characterize the submicron litho process under confocal laser scanning microscope metrology, using `linearity' and `discrimination' as process control parameters. This was found to allow for a more detailed process characterization than the usual `CD value' information alone. This also allows one to determine how the CLSM system performs on a particular type of sample and over a specified linewidth range. The measurement substrates included silicon wafers coated with 1.1 micrometers of resist and printed with a gradient of isolated lines ranging from 0.6 micrometers to 1.0 micrometers in 0.05 micrometers increments. The CLSM measurement system was `tuned' to yield optimum precision and accuracy so that measurement linearity would be well established over the range of interest. There are two types of linearities considered here as `linear dependencies:' the measured CD values versus their nominal values and the measured CD sensitivity versus exposure changes for a given focus setting. These linearities are quantified by (1) coefficients of regression (slope), (2) coefficients of determination (R-SQ), and (3) intercept values. Changes in slope values indicate process operating conditions which range from normal to extreme (under/over exposure and positive/negative defocus). R-SQ indicates metrology robustness and the intercept represents the measurement offset over a wide range of operating conditions. There are also two types of capabilities considered here: the CLSM's ability to distinguish (differentiate) 50 nm feature biases over a range of linewidths and the system's ability to differentiate structural changes as a result of focus and exposure changes. Results indicate that a tuned CLSM system can be used to monitor effects of variations in operating conditions as small as 5 mJ/cm2 in exposure energy and 0.4 micrometers defocus.

Paper Details

Date Published: 1 June 1992
PDF: 12 pages
Proc. SPIE 1673, Integrated Circuit Metrology, Inspection, and Process Control VI, (1 June 1992); doi: 10.1117/12.59781
Show Author Affiliations
Mircea V. Dusa, SEEQ Technology, Inc. (United States)
Tony DiBiase, SiScan Systems, Inc. (United States)
Harris J. Keston, SiScan Systems, Inc. (United States)

Published in SPIE Proceedings Vol. 1673:
Integrated Circuit Metrology, Inspection, and Process Control VI
Michael T. Postek, Editor(s)

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