Effects of lithographic and pattern parameters on stability of feature-edge location in electron beam lithography

As the feature size continues to decrease, a high level of accuracy in achieving the feature boundary (“edge”) as designed becomes more essential. One of the reasons for any deviation in the feature-edge location is the proximity effect due to electron scattering in the resist. However, even with a perfect proximity effect correction (PEC), the nonideal process of resist development can still lead to a deviation in the edge location. In general, a higher exposure contrast over the feature edge leads to a smaller deviation in the edge location. In this study, an analytic model is employed in understanding the effects of the lithographic and pattern parameters on the deviation in the edge location due to the uncertainty in the lithographic process. Specifically, the closed-form mathematical expression of the deviation is derived in terms of the parameters that determine the exposure contrast. The results reported in this paper should be helpful in understanding better the deviation in the edge location without time-consuming repetitive simulation and developing a PEC method that enhances the stability of the feature boundaries in the written pattern, improving the process latitude.