Fourier analysis of AIMS images for mask characterization

Roderick Koehle; Wolfgang Dettmann; Martin Verbeek

doi:10.1117/12.504216

28 August 2003 Fourier analysis of AIMS images for mask characterization

Roderick Koehle, Wolfgang Dettmann, Martin Verbeek

Proceedings Volume 5130, Photomask and Next-Generation Lithography Mask Technology X; (2003) https://doi.org/10.1117/12.504216
Event: Photomask and Next Generation Lithography Mask Technology X, 2003, Yokohama, Japan

Abstract

Mask characterization and qualification are becoming more and more difficult for high-end and alternating phase shifting masks. One choice is to use indirect methods like as SEM/AFM measurements to characterize mask performance. The indirect measurement has the disadvantage that the measured CD is not the true merit function. It is therefore tempting to use optical methods to characterize masks. The Zeiss AIMS (Aerial Image Measurement System) microscope is particular appealing for this task since it simulates the lithographic imaging optics. The key problem is the reliability and repeatability of the resulting AIMS measurements. The quality of the measurement depends strongly on the tool characteristic such as illumination stability and operator skill, e.g. for focus adjustment. In this paper we discuss the application of image processing and Fourier analysis techniques to AIMS images of periodic structures. By computing the Fourier series coefficients one obtains a very compact but complete description of the AIMS image over defocus. This computation and interpretation of the series coefficients allows to compensate many error influences such as mask rotation, tool magnification and focus adjustment. The algorithm is demonstrated on COG and alt. phase shifting mask measurements for a wavelength of 193nm and compared to the results obtained by simulation.

Citation Download Citation

Roderick Koehle, Wolfgang Dettmann, and Martin Verbeek "Fourier analysis of AIMS images for mask characterization", Proc. SPIE 5130, Photomask and Next-Generation Lithography Mask Technology X, (28 August 2003); https://doi.org/10.1117/12.504216

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