Electron Beam Block Exposure System for 256 M Dynamic Random Access Memory Lithography

The NOWEL-3 block exposure system that we developed contains a data transaction system, high-speed exposure control hardware and a column which has a block mask and mask deflectors. The block patterns are taken from LSI design data. Three kinds of format data, exposure data, mask information data, and mask fabrication data, are generated in the transaction system. The mask deflectors select one of forty-eight blocks on the mask. They are calibrated before the exposure. We exposed a 256 M-bit dynamic random access memory (DRAM) contact hole layer using this system. NOWEL-3 has good resolution and dimensional accuracy. It can expose patterns less than 0.1 µm wide. The block exposure system reduces the total number of shots required to 21.46×106, about 1/8 of that required in a conventional system. Each chip is exposed for 10.5 s. The throughput is about 10 wafers per hour (6").