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1 July 1991 64-Mbit DRAM production with i-line stepper
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This paper describes the exposure technology to manufacture 64M-bit DRAM chips with i-line (365-nm) stepper. The one-shot (conventional) exposure method was tried--a 64 M bit DRAM chip using the i-line lens of numerical aperture (NA)$EG0.50 with or without a phase-shift method--but the process margin was not sufficient in a few layers. The authors have shown that the block exposure method can be used as an exposure technology when the one-shot exposure method cannot be used. The block exposure method divides a step-and-repeat pattern within a single chip into multiple blocks and allows high-resolution exposure of each of these blocks. The stepper with the i-line lens of NAequals0.65 was used. The authors also tried to clarify the effect of coherency caused by the illumination optical system of the i-line stepper. In addition, the alignment accuracy of the block exposure method is discussed.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Hisatsugu Shirai, Katsuyoshi Kobayashi, and Kenji Nakagawa "64-Mbit DRAM production with i-line stepper", Proc. SPIE 1463, Optical/Laser Microlithography IV, (1 July 1991);

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