Analysis of Asymmetry of Printed Image by Off-Axis Incident Light onto Reflective Mask in Extreme Ultraviolet Lithography

概要

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In extreme ultraviolet (EUV) lithography, off-axis incident light on a reflective mask causes asymmetry of contrast in the edges of patterns with the critical dimension (CD) and a shift in the center position of the printed image of a line-and-space pattern, even if the line-and-space pattern has perfect symmetry and is correctly placed on a mask. In this study, we analyzed the asymmetry of the pattern edge contrast of line-and-space patterns using light intensity distribution functions which is obtained by taking inverse Fourier transform of the diffracted rays passing through the pupil. The results showed that, when only 0th- and $\pm 1$st-order diffracted rays pass through the pupil, the printed image tends to be symmetrical, regardless of any asymmetry in the amplitude and phase of the diffracted rays; but when 0th-, $\pm 1$st-, and $\pm n$th-order ($n\geqq 2$) diffracted rays pass through the pupil, the printed image tends to be asymmetrical.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2005-12-15