Y. Sohda et al., COULOMB EFFECT IN CELL PROJECTION LITHOGRAPHY, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 13(6), 1995, pp. 2419-2423
Beam blurring due to Coulomb effects is very important in cell project
ion lithography. This article reports on Coulomb effects in cell proje
ction lithography by simulation and experiment, and shows some importa
nt results. First, the Coulomb effect in a single cell is substantiall
y uniform in conventional cell projection optics. Second, refocusing i
s effective in reducing the space charge effect even in Koehler illumi
nation with a Gaussian crossover. Third, the optimum cell size in the
case of a large aperture percentage depends on the ratio of the total
exposure time in the peripheral circuit to the total settling time in
the memory cell mat. In addition, a modified mask technique is propose
d to decrease the influence of Coulomb effects on throughput. (C) 1995
American Vacuum Society.