A MEMS fabrication approach for a 200GHz microklystron driven by a small-scaled pseudospark electron beam

High performance terahertz (THz) radiation sources hold great promise for a variety of military and space applications. With micro-electro-mechanical systems (MEMS) fabrication techniques, it is possible to attain the smaller, more precisely machined resonant structures required by Vacuum Electronic Devices (VEDs) to function in these frequencies. The research presented here proposes a design and fabrication process for a micro-klystron with a targeted operating frequency of 200 GHz; being developed jointly by Duke University, the University of Strathclyde, UK, and Logos Technologies. It also analyzes the use of a pseudospark (PS) discharge as a novel electron beam source to drive the klystron. Dimensional tolerances are investigated using both analytic and numeric techniques. The incorporation of alignment structures into the fabrication process that utilize kinematic and elastic averaging effects, along with clever stacking techniques, allows submicron alignment tolerances yielding an expected power output of approximately 5W per klystron with an overall efficiency of 20%. The device proposed here, with a volume on the order of 0.01 cc, should be capable of output power densities of up to 1kW/cc. A fabrication run recently completed at MIT's Microsystems Technology Laboratories yielded promising results and 32 silicon die were successfully bonded into a stack 1.4cm tall. Difficulties remain, however, in controlling surface roughness and integrating a klystron with alignment features for parallel processing. Several alternative fabrication schemes have been proposed and another fabrication run based on these modifications is currently underway.