Technological Approaches to the Microfabrication of Planar Slow-Wave Structures for Millimeter- and THz-Band Vacuum Electron Devices

Sources of millimeter and submillimeter (terahertz) band radiation are very important in modern society due to their broad application from telecommunication to non-destructive evaluation and chemical analysis. In this work, we present a review of technological approaches for fabrication of RF structures of µVEDs. Technological approaches to the microfabrication of planar slow-wave structures (SWS) on dielectric substrates operating with a sheet electron beam are considered. Such SWSs are attractive due to the simplicity of the structure, compact dimensions, low voltage operating, and wide bandwidth. We consider lithography-based technology, deep reactive ion etching, computer-numerical-control (CNC) micro- and nano-milling, electrical discharge micromachining, and technologies based on the additive manufacturing such as three-dimensional (3-D) printing, selective laser sintering, and selective laser melting. We also describe an original approach to microfabrication of planar structures based on magnetron sputtering and CNC laser ablation. Fabrication tolerance and surface roughness provided by the considered technologies are compared.