On-Chip High-Performance Millimeter-Wave Transmission Lines on Locally Grown Porous Silicon Areas

High-performance on-chip coplanar-waveguide (CPW) transmission lines (TLs) were fabricated on locally formed porous silicon membranes on the Si wafer, and their millimeter-wave (mmW) characteristics were measured up to 110 GHz. It was demonstrated that a quality factor three times higher than that of conventional CPWs fabricated in standard CMOS on bulk crystalline Si can be obtained in mmW frequencies. The measured values of the attenuation loss were ~ 0.35 dB/mm at 60 GHz and ~ 0.55 dB/mm at 110 GHz. The obtained attenuation loss was independent of the realized TL characteristic impedance (50 and 145 Ω). These results are better than the state-of-the-art results in the literature obtained using CMOS on high-resistivity (HR) Si substrates (CMOS HR technologies). They show the potential of using locally formed porous Si membranes in mmW shielding on the Si wafer, in addition to the already demonstrated RF shielding (frequencies up to 40 GHz).