Pengcheng Li recently posted two preprints to the arXiv on the topic of proximity effect correction (PEC). In the first, he discusses the adjustment of sidewall angle simultaneously with dimension. In the second, he gives a brief but reasonably complete review of the PEC literature.
Adjustment of sidewall angle has a long and storied history of its own. Especially when using low contrast resist processes, it was common practice to “under-size and over-develop” as a global means of straightening up the wall angles. The method discussed here involves a (one-dimensional) distribution of applied doses, optimized by simulated annealing. Not surprisingly, the resulting dose profiles look much like those resulting from earlier calculations. Mr. Li goes on to compare simulated developed resist profiles with experiment. He finds good qualitative agreement.