200–330-GHz Substrate-Integrated Waveguide in BEOL of a SiGe BiCMOS Process

This letter shows the first 200–330-GHz substrate-integrated waveguide (SIW) to a grounded coplanar waveguide (GCPW) transition realized in backend-of-line (BEOL) of a SiGe BiCMOS process. The transition uses two rectangular slots and a GCPW stub, which convert a quasi-TE10 to quasi-TEM mode with the highest operating frequency of up to 330 GHz, largest operation bandwidth of 49%, and smallest transition length of
$99 \mu \text{m}$
for a silicon process-based SIW transition demonstrated to date. A back-to-back configuration with ground–signal–ground (GSG) pads on either end enables probe-based S-parameter measurement. The influence of the GSG pads is de-embedded by measuring a 50-
$\Omega $
GCPW connected by a pair of the GSG pads. A comparison of the measured and de-embedded S-parameters with the electromagnetic simulation results show that the SIW–GCPW transition operates from 200 to 330 GHz (49% bandwidth) with an average insertion loss of
$\approx 1.2$
dB per transition.