A NOVEL ELECTRON-BEAM EXPOSURE TECHNIQUE FOR 0.1-MU-M T-SHAPED GATE FABRICATION

This article reports on a novel fabrication technique for T-shaped short gates using double-layer electron-beam (EB) resist system, which provides uniform gate length across 2-in. wafers. In the proposed novel fabrication technique, a 1-mu-m PMMA (I)/0.25-mu-m PMMA (II) (HI/LOW MW) double-layer resist system is adopted to fabricate T-shaped gates. To avoid the influence of scattered electrons, the bottom PMMA (II) resist is EB-exposed through the top opening with an acceleration of 50 or 25 kV and a single-path line dose of 0.8-2.0 nC/cm. The top opening has been formed with a 25-kV Gaussian electron beam at a 120 mu-C/cm2 dosage. The developed technique has accomplished T-shaped gates with 70-nm minimum footprint and 0.1-0.2-mu-m T-shaped gates, whose yield is over 80% on wafers.