Abstract
We have developed techniques for analyzing the imaging performances of KrF exposure tools that use wave aberrations measured at 25 different image heights in a semiconductor fabrication plant. The wave aberrations are obtained by double printing lattice and square patterns and measuring their lateral registration errors. It is confirmed that multiple regression of the 3rd and 5th coma aberration coefficients permits the differences in the widths at the left and right edges of seven pairs of 250nm line and spatial patterns to be predicted to an accuracy of 9.4 nm(2σ). The results of an exposure and development simulation using wave aberrations agree with experimental results for the changes in the width of a 200 nm isolated line pattern with the focus position. This simulation is applied to quantify focus margins, which are found to be degraded due to astigmatism and spherical aberrations. Controlling the excimer laser wavelength is proposed as a means to reduce the spherical aberrations.
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