Thermal-field-emission electron optics for nanolithography

Abstract

A new column design for the 25-kV vector-scan Gaussian beam lithography system is described. A field-emission gun, consisting of a three-element electrostatic lens and Zr/O/W〈100〉 cathode operated in a thermal-field mode for current stability, is combined in a demagnifying optics with a magnetic objective lens to focus a high-current-density (1000-3000 A/cm 2) electron beam at high resolution (100-300 Å) at the wafer plane without a severe reduction in field size. Optimum beam semiangle, focus mode, and column magnification are determined. The modified system retains the original deflection coils and pattern-generation system which allows immediate implementation of existing subfield stitching, chip registration, and proximity correction software.