FABRICATION OF DOUBLE-GATED SI FIELD EMITTER ARRAYS FOR FOCUSED ELECTRON-BEAM GENERATION

Double-gated Si held emitter arrays (FEAs) capable of generating focus ed electron beams were fabricated and experimentally evaluated. The pr esent held emitter array has a vertical triode structure consisting of a conical Si tip and two gate openings (upper and lower) surrounding the tip. The lower gate with a 2-mu m-diam opening acts as an extracti on electrode controlling the emission current, and the upper one with a 3-mu m-diam opening acts as an electrostatic lens focusing the elect ron trajectories. The focusing property was evaluated by observing the spot size of a phosphor (ZnO:Zn) screen located about 20 mm apart fro m the field emitter array and biased to 1 kV. It was found from experi mental results that decreasing the upper gate voltage (V-F) down to a few volts was quite effective to generate focused electron beams. At V -F Of about 4 V, the electrons emitted from the tip were well collimat ed and a beam current of about 0.1 nA/tip was obtained. (C) 1995 Ameri can Vacuum Society.