Integration of field emitters into scanning probe microscopy sensors using focused ion and electron beams

Material processing by focused ion-beam milling and electron-beam-induced deposition was applied for the integration of field emitters into scanning probe microscopy (SPM) sensors. Geometry of the silicon probes was adapted to the integration of an emitter gate structure with a diameter in the range of micrometers. Processing of the silicon probes was modified to replace the apex by mesas with diameters between 1 mm and 15 mm. Parasitic effects originating from material processing with focused particle beams were investigated by transmission electron microscopy. A process combining focused ion-beam milling and wet chemical etching was used to remove ion-beam-induced damage and contamination due to ion implantation. Leakage current caused by absorption of precursor material during deposition of emitters was removed by thermal annealing. Field emitter structures were fabricated by focused particle beam processing revealing emission currents of 0.6 mA/tip for a gate voltage of 90 V.