Optimization of silicon field-emission arrays fabrication for space applications

Optimization of fabrication of silicon field-emission arrays has been carried out on 4 in. silicon wafers for field-emission electric propulsion neutralizer application. A mixture of SF₆, O₂, and Ar for silicon tip etches has been optimized to improve the uniformity and process repeatability. A thin aluminum nitride (AlN) film has been coated on gated emitter arrays to enhance the field at the tip and to protect tips from ion bombardment. A statistical analysis of emission characteristic shows a narrow distribution of the turn-on voltage from array to array, which makes it possible to achieve a few milliamperes current emission by connecting several arrays in parallel. Lifetime tests over 1000 h have been carried out on single arrays, producing in excess of 10 μA of emission current under continuous mode of operation. © 2004 American Vacuum Society.