Integrated Stacked Parallel Plate Shunt Capacitor for Millimeter-Wave Systems in Low-Cost Highly Integrated CMOS Technologies

This letter presents a stacked parallel plate (SPP) shunt capacitor (SC) that benefits from metal stack increment with process nodes advancement. It demonstrated high quality (
$Q$
) factor and high self-resonance frequency (SRF), promoting the design of analog integrated circuits (ICs) in low-cost highly integrated CMOS technologies at the millimeter-wave (mm-wave) frequency range. As a proof-of-concept, an analytical-equation-based design method is also proposed and three ac-grounded capacitors: 300; 600; and 900-fF, are implemented in STMicroelectronics (STM) 55-nm process. Characterization is performed up to 100 GHz. An effective capacitance density of 0.8
${\mathbf {fF}}/\mu \mathbf {m}^{\mathbf {2}}$
is obtained. Measurements show
$Q$
-values reaching up to 14.7 at 100 GHz and equivalent input series resistances with flat wideband behavior reaching at most an average of 0.55
$\Omega $
. SRFs of 140 GHz for the 900-fF SPP-SC up to 368 GHz for the 300-fF SPP-SC are also determined from measurements: the highest SRFs for such large capacitances to the authors’ knowledge.