Sub-100 nm Lithography with KrF Exposure Using Multiple Development Method

In this paper, a novel resist process technique using a chemically amplified resist with a multiple development method for improving photolithography resolution is described. By means of this technique, resist lines are formed at the edge position between the bright and dark fields of a photomask, and the repeating frequency that is more than the cutoff frequency of optics (ν c =1/ P c =2 NA /λ) can be delineated using a conventional exposure system. In the experiment, a grating resist pattern with a pitch of 200 nm was obtained using a conventional 0.6 NA KrF exposure system and a 400 nm pitch photomask pattern.

The pitch was less than the diffraction limit of 207 nm (=0.5λ/ NA ) in the optical system used, which cannot be realized by a conventional resist process even with resolution enhancement techniques such as off-axis illumination and phase-shifting mask.