The Composite Tip Field Emitter Array Preparation Process Research

Field emitter array (FEA) cathode is a core component of vacuum microelectronic device, due to its unique characteristics of small size,low power consumption, high response speed, anti-radiation, broad temperature range an so on. It has been widely used in display device, microwave tubes, sensors and X-ray tubes. In this paper a compounded field emitter array cathode of Mo-LaB6 FEA was fabricated using new material and unique process. It combined the advantages of LaB6 and Mo material, which could improve the current density and emission stability, depending on the characteristics of LaB6 of low work function, high melting point and Mo of high conductance, high chemical stability.Firstly, the manufacturing technologies of compounded field emitter arrays were studied and two programs were carried out involving step mode and coating mode in this paper. Both of them adopted the similar fabricating process, including lithography, oxygenation, etching, sputtering of the gate and the deposition of emitters. In the step mode, molybdenum with 200nm was first deposited on the silicon substrate, and then LaB6 was deposited on the Mo-step to form emission tips. In the coating mode, Mo was first evaporated to form tips and then the LaB6 film was coated on the Mo-tips. In addition, the process parameters of the two programs were discussed in detail and a Mo-LaB6 FEA with excellent appearance was successfully prepared.Some reasons leading to the failures of fabricating Mo-LaB6 FEA were discussed in this paper, including the grid's abscission, oxidation of cathode and anode, micro-burrs on the tip surfaces, desquamation of tips and the variation of film components. Aiming at those problems, some possible ways were proposed, including annealing, aging process and hydrogenation treatment. The results of measuring emission performance showed that, the grid's abscission was overcome through annealing and the oxidation layer of cathode and anode was removed by hydrogenation treatment. Furthermore, the micro-burrs could be strained effectively through the aging process. The above studies took effect on the fabrication of compounded field emitter arrays further. Finally, the package and field emission measurements of fabricated Mo-LaB6 FEA were carried out. The package process consisted of assembly, air exhaust, degassing, sealing and getter activation. Before the performance testing, the micro-burrs of the tip surfaces were eliminated by aging process. The test circuit was devised on the basis of traditional Spindt-FEA test circuit. According to the measuring results, it demonstrated the feasibility of Mo-LaB6 compounded field emitter arrays.