Performance of a submicron litho process under CLSM metrology with linearity and discrimination measurements

Mircea V. Dusa; Tony DiBiase; Harris J. Keston

doi:10.1117/12.59781

1 June 1992 Performance of a submicron litho process under CLSM metrology with linearity and discrimination measurements

Mircea V. Dusa, Tony DiBiase, Harris J. Keston

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Proceedings Volume 1673, Integrated Circuit Metrology, Inspection, and Process Control VI; (1992) https://doi.org/10.1117/12.59781
Event: Microlithography '92, 1992, San Jose, CA, United States

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.

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Mircea V. Dusa, Tony DiBiase, and Harris J. Keston "Performance of a submicron litho process under CLSM metrology with linearity and discrimination measurements", Proc. SPIE 1673, Integrated Circuit Metrology, Inspection, and Process Control VI, (1 June 1992); https://doi.org/10.1117/12.59781

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KEYWORDS

Metrology

Semiconducting wafers

Process control

Critical dimension metrology

Inspection

Integrated circuits

Silicon

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