Nanopatterns beyond the Feature Size Limit via Bilayer Electron Beam Lithography for Nanoelectronics Applications

We report a patterning technique called bilayer e-beam lithography (BEBL), which employs direct-writing electron beam lithography on a bilayer photoresist system to achieve outline-like features with line widths smaller than the original writing pattern. This method leverages the subtractive outcome of two opposite photoresist layers─one positive and one negative─following e-beam exposure and development. The critical dimension (CD) of these outline-like BEBL features can be readily adjusted by manipulating the exposure and development conditions of the photoresists. We have demonstrated both line/space and via patterns using BEBL, with the CD of line/space patterns ranging from 6 to 48 nm. Note that a CD of 6 nm is not the BEBL’s theoretical limit. Furthermore, by incorporating an additional cross-patterning step, the line/space patterns can be converted into via patterns. Besides, we demonstrated the patterning flexibility of BEBL; outlines of complex features such as symbols and numbers were fabricated. BEBL holds promising potential for broad applications in nanoelectronics and serves as a valuable tool for fundamental research in nanoscience.