Investigation of a planar microtriode fabricated with direct write nanolithography using electron beam induced deposition

A planar micro-triode with field emission cathode is investigated. The metal pattern for coarse and fine voltage feed lines, signal detection lines, and shielding patterns are designed by Computer Aided Design (CAD) and fabricated in 1 μm technology. Electron optical performance and field distribution is calculated using numerical electron optics programs for structures in 1 μm technology and 0.3 μm technology. A silicon chip coated with thick silicon oxide is used as substrate material. The coarse metal pattern is fabricated using an optical contact printer and etching. The fine metal pattern is produced using electron beam lithography exposure and metal lift-off. Finer connecting lines and the field emitter tip as well as extractor structures are fabricated by direct write nanolithography with electron beam induced deposition (EBID). For deposition, a platinum containing precursor is used. Deposition is performed in an experimental mask repair system at very low energies and high placement precision. For prolonged lifetime an ion mirror is incorporated. Emission is observed using a scintillator-anode. Investigations are performed in an UHV system, as well as in high vacuum and in air. Measurements of currents from deposited emitters are performed in a triode arrangement using 3kV anode voltage, grounded extractors and -105 V as cathode potential. The emission current is recorded using a computer controlled recording system with msec resolution to monitor short term variations also in long term measurements. Emission currents of nA are observed without ion mirror in action over several days, and show variations up to 50% due to vacuum conditions.