Wideband, High Efficiency On-Chip Monolithic Integrated Antenna at W-Band Using Miniaturized Cavity and Through Silicon Via

We present a W-band on-chip planar inverted-F antenna (PIFA) featuring high efficiency and wide bandwidth. The proposed on-chip antenna (OCA) incorporates a miniaturized <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.12~\lambda _{{0}}^{{2}}$ </tex-math></inline-formula>-sized substrate-integrated air cavity (SIC) that creates a high dielectric discontinuity between air and silicon enabling an increase in radiation efficiency by suppressing the parallel plate modes. Forming air cavities in the substrate avoids the need for precise heterogeneous packaging, in contrast with integrating dielectric resonators or superstrate dielectrics with OCAs. To the best of the authors’ knowledge, a through-silicon via (TSV) was incorporated into a commercial silicon-based OCA die for the first time, enhancing the electrical connection to the off-chip ground and mechanical stability. The OCA is fabricated using a 180 nm SiGe BiCMOS process, with CMOS-compatible postprocessing for SICs and TSVs. The proposed OCA complies with various design rule check (DRC) guidelines, including minimum trace width sizing and metal density considerations to achieve a high manufacturing yield. The SIC is created by etching the bottom silicon substrate using a deep reactive-ion etching (DRIE) process. We manufacture an Ag TSV by filling the SIC with Ag epoxy to prevent expensive postprocessing. Measurements of the radiation patterns of the W-band antenna were performed using a robotic arm. The PIFA achievesa −10-dB bandwidth from 89 to 105 GHz with a fractional bandwidth of 16.3%. It also delivers an 11.4 GHz 1-dB gain bandwidth with a maximum realized gain of 1.6 dBi, corresponding to a peak efficiency of 72%. This research leverages commercial SiGe BiCMOS technology to achieve high efficiency and wide bandwidth, with TSVs providing a robust ground plane and potential for use as signal paths in monolithic integrated circuits.