Observation of backward-wave oscillations in silicon-MEMS beam-wave interaction circuits at 0.1 THz

We report a W-band backward-wave oscillator using micro-fabrication technologies by which a fully 3-dimensional slow-wave interaction circuit is successfully employed on multi-bonded silicon wafers. MEMS (micro-electromechanical systems) technologies such as deep RIE (reactive ion etching) and thermocompressive hermetic bonding are applied to achieve highly accurate dimensional structures for high frequency regime (>;100 GHz). A successful implementation of the slow-wave structure with high aspect ratios between in-plane and out-of-plane dimensions was confirmed by the return loss simulation and measurement. A thermionic dispenser cathode of 15 kV produced more than 91 mA electron beam current and achieved 90% beam transmission through the interaction circuit after vacuum integration. The RF measurement of the UHV-sealed interaction circuit showed backward-wave oscillations at 0.1 THz driven by an external small signal from a Gunn diode.