Sub-10-nm electron beam lithography with sub-10-nm overlay accuracy

Stable sub-10-nm lithography was achieved using a 100-kV electron-beam naonolithography system. 8-nm-wide lines were formed using a high resolution spin-coatable Al₂O₃ resist, and even at the corner of a wide field of several-hundred micrometers square, the lines were about 10-nm wide. The overlay accuracies in |mean|+2σ were about 5 nm at the field center and sub-10 nm at the field boundaries. The high stability of exposure and the high overlay accuracy were obtained not only by the high-performance lens and the high acceleration voltage but by high stability of the stage and the beam. A method of repeating nanolithography with high overlay accuracy and substrate etching was developed. It allows us to form sub-10-nm-wide standing lines within the field, using a highly sensitive positive-tone resist. These technologies are promising to apply to high performance nanodevices like integrated single-electron devices.