Limitation of the Kirchhoff boundary conditions for aerial imagesimulation in 157-nm optical lithography |
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Authors: | Yeung M.S. Barouch E. |
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Affiliation: | Dept. of Manuf. Eng., Boston Univ., MA; |
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Abstract: | The aerial images of half-wavelength features with 0° and 180° phases obtained by using the Kirchhoff boundary conditions are compared with those obtained by using rigorous electromagnetic field computation for 248-nm lithography and 157-nm lithography. The discrepancies between the aerial images computed by the two methods are large at both wavelengths, but they are much larger for TM polarization at the wavelength λ=157 nm. These discrepancies are due to diffraction effects in the aperture regions, which are more pronounced at λ=157 nm because of the larger ratio of the thickness of the chromium absorber to the wavelength required at λ=157 nm for a given attenuation factor. This shows that diffraction effects in the aperture regions must be included when simulating aerial images in 157-nm lithography |
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