Development of Extreme Ultraviolet Interference Lithography System

Extreme ultraviolet interference lithography was carried out at the long undulator beamline in NewSUBARU. It was confirmed that the spatial coherence length is 1.1 mm using a 10-mu m-wide slit in the Young's double slit experiment. A 25-nm half pitch (hp) resist pattern was successfully replicated by extreme ultraviolet interference lithography (EUV-IL) utilizing a two-window transmission grating pattern of a 50-nm line and space (L/S). For the replication of a 20-nm L/S resist pattern by EUV-IL, we contrived a fabrication process that is suitable for a transmission grating pattern of 40-nm L/S and smaller. Employing a hard-mask process with a silicon dioxide (SiO2) layer on a tantalum-nitride (TaN) layer in the fabrication of a two-window transmission grating, we successfully achieved five times larger dry-etch selectivity in comparison with a non-hard-mask process. As a result, we confirmed the ability to apply this process to a 40-nm hp grating. (C) 2010 The Japan Society of Applied Physics