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Optical Linewidth Models: Then and Now



Robert D. Larrabee, Richard M. Silver, M P. Davidson


In the late 1970's, Dr. Diana Nyyssonen demonstrated that NIST could optically calibrate photomask linewidth standards that were narrower than the classical resolution limit of a conventional bright-field microscope. She equated the known position of the line edge on a theoretically calculated line profile (i.e., taking diffraction into account) to the otherwise unknown edge position on the corresponding observed line profile. Since, at that time, there was no other way to accurately identify the position of the geometrical edge of the line on measured optical-intensity line profile from first principles, NIST would not have been able to issue accurate photomask linewidth standards without her theoretical model. NIST has initiated a program to re-examine Nyyssonen's model to see how well it meets today's requirements for linewidth standards. Fortunately, Dr. Mark Davidson had conferred with Dr. Diana Nyyssonen about her model before her untimely death, and he was able to improve the utility and accuracy of her model. He removed some of its assumptions and improved the efficiency of computation to the point where the computations could be done on a desk-top personal computer. This paper details the results of the comparisons.
Proceedings Title
Proceedings of SPIE, Metrology, Inspection, and Process Control for Microlithography XIII, Bhanwar Singh, Editor
Conference Dates
March 15, 1999
Conference Location
Santa Clara, CA, USA
Conference Title
Modeling: Optics


linewidth, metrology, modeling, photomask, standards


Larrabee, R. , Silver, R. and Davidson, M. (1999), Optical Linewidth Models: Then and Now, Proceedings of SPIE, Metrology, Inspection, and Process Control for Microlithography XIII, Bhanwar Singh, Editor, Santa Clara, CA, USA (Accessed April 25, 2024)
Created May 31, 1999, Updated October 12, 2021