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3D Monte Carlo modeling of the SEM: Are there applications to photomask metrology?



John S. Villarrubia, Andras Vladar, Michael T. Postek


The ability to model the effect of fields due to charges trapped in insulators with floating conductors has been added to JMONSEL (Java Monte Carlo simulator for Secondary Electrons) and applied to a simple photomask metal on glass geometry. These capabilities are prerequisites if model-based scanning electron microscope (SEM) metrology is to be extended beyond wafer to photomask applications, where such samples must frequently be measured. Model-based SEM is an alternative to the customary threshold- or gradient-based approach. It is more demanding inasmuch as it requires a model of the physics of image formation, but the reward is greater accuracy, lower sensitivity to secondary sample characteristics (e.g., edge shape) that affect the intensity, and information about 3D geometrical shape (not simply the width) of the measured features. The prerequisites are ability to measure a signal, such as the SEM image, that is sensitive to changes in the parameters one wishes to measure and a model that describes the relationship between the signal and the parameters. The simulation shows the development of the potential energy barrier to electron escape during an initial transient charging-up phase, accompanied by increasing electron recapture and stabilization of the average yield.
Proceedings Title
Proc. SPIE Scanning Microscopies
Conference Dates
September 16-18, 2014
Conference Location
Monterey, CA
Conference Title
SPIE Scanning Microscopies 2014


charging, dimensional metrology, model-based library (MBL) metrology, photomask, scanning electron microscopy (SEM)


Villarrubia, J. , Vladar, A. and Postek, M. (2014), 3D Monte Carlo modeling of the SEM: Are there applications to photomask metrology?, Proc. SPIE Scanning Microscopies, Monterey, CA, [online], (Accessed May 22, 2024)


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Created October 23, 2014, Updated November 10, 2018