14 September 2001 Measurement of transmittance variation of projection lenses depending on the light paths using a grating-pinhole mask
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Abstract
A new method of measuring across pupil transmittance variation (APTV) is proposed. APTV measurement can be performed using a grating-pinhole (GP) mask, which comprises grating stricture in a small circular area, small-sigma illumination, and common wafer process. A measurement mark consists of twelve kinds of GPs with the same duty ratio, different pitches, and different orientations. First-order beams generated at GPs with the same intensity travel through the lens and reach the wafer, in which the relative intensities of first-orders are measured and compared. Transmittance distribution of 24 points across the pupil plane associated with approximately one image point is measured. In addition, exposure field dependency of APTV is measured by arranging some identical sets of GPs across the exposure field. We have successfully measured APTV for an argon fluoride excimer laser (ArF) exposure tool as a demonstration of this method. The measurement error of relative intensity due to mask fabrication error has been estimated to be less than 0.4%. The influences of APTV on lithography have been investigated. Simulation results indicated that unbalanced APTV causes asymmetric modification of a symmetric pattern or periodic pattern edge.
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Kazuya Sato, Kazuya Sato, Soichi Inoue, Soichi Inoue, } "Measurement of transmittance variation of projection lenses depending on the light paths using a grating-pinhole mask", Proc. SPIE 4346, Optical Microlithography XIV, (14 September 2001); doi: 10.1117/12.435737; https://doi.org/10.1117/12.435737
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