Mini-column silicon field-emitter arrays

Abstract

We report emission data of silicon field emitter arrays fabricated with the ultimate goal of their integration within a planar lens structure for beam focusing experiments. The field emitters have been fabricated as linear arrays (with 20 μm separation between tips), square arrays (with 12 μm tip-to-tip separation), and single tips. The emitters themselves are formed on columns approximately 0.7 μm in height and 0.4 μm in diameter, and have gate aperture diameters as small as 1.1 μm. Two types of field emitter tips have been fabricated: One has been formed via isotropic etching of silicon in an SF6 plasma, the second using an orientation-dependent silicon wet etching procedure. Both have been sharpened with an oxidation process, and tip radii as small as 4 nm have been obtained. During testing, 14.4 μA of anode current was obtained from a single tip. From a 100 tip array, 3 mA of current was measured at a gate voltage of 85 V. From a 10 000 tip array, 14.5 mA was obtained.