Grid-Controlled 100 Kv Electron Beam Source for SCALPEL

The SCALPEL E-beam lithography tool requires an extremely uniform, high emittance E-beam to illuminate the Mask. The existing SCALPEL source utilizes a pure metal cathode operating in the temperature limited mode, thus having limited total emission current available. The usable emitter size of this cathode is constrained by its direct heating scheme, which sets un upper limit for the beam emittance. Furthermore, to generate a uniform beam, a conventional source should be designed to have a high cut-off voltage, which precludes an efficient electronic beam current control. We have studied the possibility of implementing a large area flat cathode and fine control grid mesh combination, potentially capable of providing high emission uniformity, high beam current and low beam control voltage.