Proximity effect correction for electron beam lithography : Highly accurate correction method

A new formula for proximity effect correction is discussed. The formula is represented by a series expansion. When infinite terms are used, the formula gives accurate optimum correction doses. The correction accuracy of the new formula is evaluated for the worst case scenario and compared with the conventional formula. It is shown that (1) the new formula suppresses correction errors to less than 0.5% for the deposited energy and (2) dimensional errors are less than 4 nm, even if only the first 3 terms are calculated for critical patterns. By using the new formula, the proximity effect correction can be carried out with sufficient accuracy, even for making reticles of 1 Gbit or higher-capacity DRAMs.