Contrast mechanisms in high-resolution contact lithography: A comparative study
We compare three different approaches to high-resolution contact lithography with special emphasis on contrast mechanisms for subwavelength structures. Masks with protruding metal absorbers, masks with absorbers embedded in the transparent background, and masks with air gaps and recessed absorbers are studied. Using the Green's tensor technique we compute the light intensity distribution in the photoresist. The intensity and contrast functions are investigated for different mask geometries (absorber thickness, height of protruding elements), and the difference between chrome and gold as absorber material is discussed. Our results show that embedding the absorbers in a transparent mask material enhances the transmitted intensity and the contrast compared with a mask having protruding metal absorbers. A further improvement is achieved by a topographically patterned mask with air gaps and recessed absorbers. Optimized mask dimensions can be found for which the contrast and the depth of focus are increased. (C) 2001 Elsevier Science B.V. All rights reserved.
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Keywords: contact lithography ; contrast mechanism ; electric field distribution ; scattering calculation ; Green's tensor technique ; Evanescent Near-Field ; Light-Coupling Masks ; Optical Lithography ; Photolithography ; Lensless
Record created on 2011-04-11, modified on 2016-08-09