EFFICIENCY OF ELECTRON-BEAM PROXIMITY EFFECT CORRECTION

The trend of increasing pattern data volume, together with decreasing critical dimensions, causes correction of proximity effect to be conti nually more time consuming and expensive. A tradeoff exists between sp eed and accuracy. A given correction method may be judged efficient if the direct computational overhead needed to achieve a predetermined l evel of accuracy is small. Some basic principles relating to efficienc y are derived. An optimal correction algorithm follows naturally from the analysis. Forward and backward scattering have greatly differing r anges, and correspondingly differing computational requirements. The t wo processes are easily separated analytically. Dose correction is use d to offset backscattering, while edge displacement is used to offset forward scattering. The only direct computational overhead is the loca l pattern density. All other necessary parameters are precomputed, and accessed by memory lookup.