Silicon-Based Technology for Integrated Waveguides and mm-Wave Systems

IC processing is used to develop technology for silicon-filled millimeter-wave-integrated waveguides. The frontend process defines critical waveguide sections and enables integration of dedicated components, such as RF capacitors and resistors. Wafer gluing is used to strengthen the mechanical support and deep reactive-ion etching forms the waveguide bulk with smooth and nearly vertical sidewalls. Aluminum metallization covers the etched sidewalls, fully enclosing the waveguides in metal from all sides. Waveguides are fabricated with a rectangular cross section of 560 μm × 280 μm. The measured insertion loss is only 0.12 dB/mm at 105 GHz. The optimized planar transition, the components of a beam-forming network, and a slotted waveguide antenna array are fabricated as further technology demonstrators. The broadside radiation of the antenna array has a beam steering of 63° using a frequency bandwidth of 17 GHz, and a half-power beamwidth of 3.9° at 94.5 GHz with a side-lobe level of -13 dB. All demonstrators exhibit close matching to the simulated designs, a result of the high resolution of the lithography process that allows fine control of the critical waveguide dimensions and the formation of efficient signal transitions.