200 and 400 GHz Schottky diode multipliers fabricated with integrated air-dielectric (substrateless) circuitry

Abstract

A novel semiconductor fabrication process has been developed at the Jet Propulsion Laboratory for realizing millimeter and submillimeter-wave monolithic integrated circuits. The process enables integration of the active devices, Schottky diodes, with planar metallic transmission lines. To reduce the RF losses in the passive circuitry, the semiconductor substrate under the transmission lines is etched away, leaving the metal suspended in air and held only by its edges on a semiconductor frame. The frame also allows the circuit to be handled and mounted easily, and makes the whole structure more robust. Moreover, this technology allows for the diodes to be positioned precisely with respect to the circuitry and can be scaled for higher frequency applications. Metallic beam-leads are used extensively on the structure to provide mechanical ‘handles ’ as well as current paths for both DC grounding and diode biasing. To demonstrate the utility of this technology, broadband balanced planar doublers based on the concepts in [1] have been designed in the 200 and 400 GHz range. Extensive simulations were performed to optimize the diodes and design the circuits around our existing device fabrication