Shipley's chemically amplified DUV resists UVN-2 (negative tone) and UV-5 (positive tone) have been studied for their high resolution capabilities in electron beam lithography. UV-5 is also capable of negative tone behaviour in case of e-beam overexposure. This effect is shown to be due to direct electron beam cross linking superimposed on the normal catalytically induced positive tone behaviour. The ultimate resolution for 100 nm thick UVN-2 is below 50 nm for single lines, when using the shortest possible developing time in order to prevent swelling. The best obtained positive tone resolution of UV-5 is 50 nm for single trenches and 120 nm for 1:1 lines and spaces. The best obtained negative tone resolution of overexposed UV-5 is below 90 nm. This negative tone behaviour is accompanied by a 60% swelling of a 100 nm thick layer, which swelling is most probably related to the relatively long developing time. This swelling is not observed for a 485 nm thick UV-5 layer.
Van Delft, F. C. M. J. M., & Holthuysen, F. G. (1999). DUV resists in negative tone high resolution electron beam lithography. Microelectronic Engineering, 46(1), 383–387. https://doi.org/10.1016/S0167-9317(99)00112-4