Studies on the interaction between thin film materials and Mo field emitter arrays

A simple method for the evaluation of materials suitable for the fabricatio n of field emission vacuum microelectronic devices is presented. Since ther e can be a wide range of electron and ion interactions with the device, it is important to be able to quickly assess if a material may have a particul ar adverse effect on emission performance under operational conditions. The technique is based on the sensitivity of a large field emitter array to th e outgassing or desorption of gas species from thin films under electron be am excitation. We found that Mo field emitter arrays degraded rapidly with stainless steel anodes coated with various oxide materials. The extent of d egradation was found to be the most rapid with SiO2, Si3N4, and MoO3 thin f ilms. Stainless steel anodes with Mo and Nb thin films show a faster degrad ation rate than stainless steel anodes, most likely because of native oxide s grown during processing and handling. The emission behavior in the presen ce of Ir, Pd, Al, Zn, and Ti metal films and barrier materials like C and T aN is similar to stainless steel reference data. We find that once the oxid e films are covered with barrier layers like C and TaN, emission decay rate s approach the values obtained with stainless steel reference anodes. The o bserved emission current degradation is consistent with a model based on th e liberation of oxygen from the surface of electron beam bombarded material s. Using controlled oxygen exposure experiments, we have determined the equ ivalent local oxygen pressures in the presence of various thin films. We fo und that with thin films of Nb, ZrO2, Ta2O5, MgO, Nb2O5, and Al2O3, the emi ssion degradation is akin to having a local O-2 partial pressure in the 1x1 0(-7)-1x10(-6) Torr range and with Mo, MoO3, Si3N4, and SiO2, this is equiv alent to having local O-2 pressures of 1x10(-5) Torr. (C) 2000 American Vac uum Society. [S0734-211X(00)01204-X].