Development-free grayscale electron beam lithography on poly (methyl methacrylate)

This paper presents and describes the validation of a method for directly fabricating three-dimensional (3D) structures on a poly(methyl methacrylate) (PMMA) membrane using grayscale electron beam lithography (EBL). The method enables precise control of exposure dose, allowing the depth resolution of fabricated structures to be controlled to less than 1 nm. Moreover, the development-free approach of the method reduces processing steps while avoiding the problems of excessive roughness and poor continuity typically encountered in conventional EBL grayscale exposure methods. The differences between two-dimensional and 3D proximity effect correction in this method were determined. Additionally, a dose correction method based on height differences was proposed to increase the edge steepness of the fabricated structures.