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3 November 1994 Topography effect in half-tone phase-shift mask for window formation
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Proceedings Volume 2254, Photomask and X-Ray Mask Technology; (1994)
Event: Photomask Japan '94, 1994, Kawasaki City, Kanagawa, Japan
Three types of half-tone phase-shift masks (shifter overcoated, substrate etched, and monolayer) have been investigated for window pattern formation from the viewpoint of lithographic performance (depth of focus, DOF and window size fidelity). A 0.35 micrometers window pattern was formed by using an NA equals 0.6, (sigma) equals 0.3, i-line stepper onto a bare-Si wafer coated with 1 micrometers thick novolac positive type resist. Mask bias value necessary for 0.35 micrometers window formation depended on shifter structure; 0.05 micrometers in the shifter overcoated, 0.075 micrometers in the substrate etched and 0.025 micrometers in the monolayer. However, the lithographic performance of every half-tone mask was almost the same; 1.6 micrometers wide DOF was obtained in 0.35 micrometers window with these three masks, in comparison with 1.0 micrometers DOF with a conventional mask. This fact indicates that topography effect only works as mask bias; vertical or tapered phase shifter edge reduces pattern size owing to the scattering exposure light. Therefore, mask bias must be adjusted for each mask structure. In conclusion, all mask structures evaluated are available for window formation.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Shinji Ishida, Yohko Iwabuchi, Tadao Yasuzato, and Kunihiko Kasama "Topography effect in half-tone phase-shift mask for window formation", Proc. SPIE 2254, Photomask and X-Ray Mask Technology, (3 November 1994);

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