ELECTRON-OPTICAL SYSTEM FOR THE X-RAY MASK WRITER EB-X2

An electron optical system that yields a beam voltage of 100 kV and a beam edge resolution of 20 nm was developed for a variably shaped elec tron beam writing system, the EB-X2. In order to improve the beam edge resolution, the objective lens and main deflector were designed on th e basis of the uniform field concept, and the optimum beam half-angle was determined by beam profile calculations. The optimized design prov ides a beam edge resolution of 20 nm for a 650-mu m-square deflection field and a beam current of 250 nA. Given the high acceleration voltag e, it is possible that the electron optical column could be too high t o fit into a clean room. To shorten the height of the electron optical column, the lens configuration was carefully examined. The results sh ow that the height of the column is a minimum when the first shaping a perture is placed in the principal plane of the illumination lens. Thi s finding enabled us to reduce the height of the column to 880 mm. The electron optical column was constructed and the beam edge resolution was measured. The measured values agree well with the calculated ones, which confirms that the constructed column has the performance expect ed of the EB-X2 electron optical system. (C) 1997 American Vacuum Soci ety.