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18 September 1995 Influence of shape of the illumination aperture on the intrafield image displacement
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The intrafiled image displacement with the various illumination apertures (conventional, quadrupole, annular) was studied and its influence on the actual overlay accuracy was estimated quantitatively. It was found that deviation of the distortion components of modified illumination apertures from conventional aperture (NA 0.57, (sigma) 0.6) brought about the overlay between conventional and modified illumination-exposed layers within +/- 10nm in the full-field (22mm2). Quadrupole and annular apertures with high oblique illumination ((sigma) out > 0.6) showed relatively lower in absolute magnitude of distortion components and narrower in fluctuation span across the field compared to conventional aperture. However, apertures with low oblique illumination ((sigma) out < 0.5), also having small opening area, revealed the contrary results. In the telecentricity study, modified illumination apertures were seen to have the better characteristics than conventional apertures, which implies that more serious deviation of overlay could occur if the two layer were exposed at the different defocus conditions, let alone the different illumination apertures. From these results, it seems obvious that there are some relationships between the intrafield image displacement of the projection lens and the geometrical shape of the illumination aperture. In thep ractical reason, we have suggested the scheme with the magnification correction for the exposure step to minimize the overlay errors, which has its basis on the telecentricity characteristics for each apertures.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Byeong-Chan Kim, Young Jin Song, Hong-Seok Kim, and Jaejeong Kim "Influence of shape of the illumination aperture on the intrafield image displacement", Proc. SPIE 2638, Optical Characterization Techniques for High-Performance Microelectronic Device Manufacturing II, (18 September 1995);


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