Double-layer resist films for submicrometer electron-beam lithography

This paper describes a double-layer resist-film technique for submicrometer electron-beam lithography. The results of computer simulation and lithography experiments carried out on PMMA/MPR (LO/HI) and MPR/PMMA (HI/LO) double-layer films are reported in full detail. It is shown that an undercut profile suitable for the lift-off processing can be reproducibly obtained by the use of the LO/HI structure over a wide range of electron-beam exposure dose, while the HI/LO structure is of great advantage in the fabrication of lift-off metal gates with a mushroom-like cross section.