NOWEL-2 VARIABLE-SHAPED ELECTRON-BEAM LITHOGRAPHY SYSTEM FOR 0.1-MU-M PATTERNS WITH REFOCUSING AND EDDY-CURRENT COMPENSATION

We have developed a variable-shaped electron beam (EB) lithography system which we call NOWEL-2. The system has the following features: (1) a short objective lens and a four-stage major deflection system; the landing angle at the corner of the 1.6 mm square major field is less than 2 mrad, and patterns from 0. 1 to 3.0 mum are well resolved over the whole deflection field, (2) 20-bit digital-to-analog converter and high-precision current output amplifier, in which the least significant bit (LSB) corresponds to 0.0025 mum; linearity error is less than 1/4 LSB at 23 +/- 5-degrees-C, (3) refocusing and refocus-flyback; the edge sharpness of a 3 mum square beam was improved from 0.5 mum to 0.25 mum, (4) eddy current compensation; for a 100 mum electromagnetic jump, the waiting time is less than 50,us, (5) continuously moving stage mode exposure; beam position accuracy is about 0.05 mum (3sigma).