Low-Loss Differential Semicoaxial Interconnects in CMOS Process

Design, characterization, and modeling of differential semicoaxial interconnects based on a standard 0.18-mum CMOS process are presented for the first time. The differential semicoaxial line shows a low differential-mode attenuation constant of ~1.00 dB/mm at 50 GHz and a slow-wave factor above 3.1 over a wide frequency range. The characteristics of differential semicoaxial lines for differential mode, common mode, slow-wave effect, and coupling effect are also investigated in details based on the measured mixed-mode S-parameters. The lumped RLGC circuit is adopted to model the CMOS differential semicoaxial lines. An excellent agreement between the measured and modeled results is obtained up to 50 GHz