Hollow beam electron gun for electron beam reducing image projection system: Computer simulation

A new hollow beam electron gun with an annular emission area is described. A cathode image is focused at the contrast aperture of the projection lens system, and the mask is irradiated by a uniform intensity electron beam which is conjugate to a flattop region near the crossover. The emittance is 7.8 mm mrad for a beam energy of 100 keV. Brightness can be varied from 8 x 10(2) to 4.5 x 10(3) A/cm(2)sr by changing only the cathode temperature. The gun crossover, the flattop area, and the cathode image axial positions can also be varied widely, without changing gun brightness and emittance,by changing the fun control anode potential. The emission current can be reduced by reducing the "ratio (emission area radial width/maximum emission area radius) of the cathode surface" without changing the emittance and with little brightness change. Using this simulated electron gun, the basic electron optics of an electron beam projection lithography system with a hollow beam is designed.