High field breakdown of narrow quasi uniform field gaps in vacuum

Abstract

The challenge in vacuum microelectronic device design is to be able to stress a given micrometric gap to relatively high voltages without threat of a breakdown, which, in effect could destroy the device. In order to obtain basic vacuum insulation data related to the regime of vacuum microelectronics, the prebreakdown and breakdown characteristics of narrow gaps in the range of 3–25 μm were extensively investigated. The observed prebreakdown current was related to field emission from atomic scale microprotrusions or planar emission sites; the emission from these sites eventually produces breakdown. A single spark breakdown caused damage to both the anode and cathode. The dc glow discharge conditioning in air improved the insulation capability of narrow gaps (3–25 μm) significantly. The breakdown strength of a 5 μm gap after conditioning was as high as 5×108 V/m, which is the highest value reported in literature for broad area electrodes. It is shown that the electric field evaporation of metal ions from the electrode surface at an electric field E≅1010 V/m is able to instigate breakdown of the gap even under high vacuum conditions. Electric field evaporation can occur both at the cathode and anode surfaces to create the breakdown conditions. The breakdown data obtained in the micrometric gap regime is very valuable in the design of field emission displays and other vacuum microelectronic devices.