Y. Gotoh et al., IMPROVED ALIGNMENT ACCURACY USING LENS-DISTORTION CORRECTION FOR ELECTRON-BEAM LITHOGRAPHY IN MIX-AND-MATCH WITH AN OPTICAL STEPPER, JPN J A P 1, 36(12B), 1997, pp. 7541-7545
The mix-and-match use of an electron-beam (EB) lithography system and
an optical stepper is an effective approach to achieving higher resolu
tion while maintaining high throughput in the fabrication of Gbit DRAM
s and advanced ASIC devices. In this approach, the highly accurate ali
gnment of patterns exposed by different lithography methods is essenti
al. In this paper, the lens distortion of the optical stepper is exami
ned and distorted patterns are aligned with an EB lithography system.
The overlay accuracy in this mix-and-match application was 51.4 nm (3
sigma) which corresponds to Gbit DRAMs fabrication.