Model of Substrate Capacitance of MOSFET RF Switch Inspired by Inverted Microstrip Line

The subject of the paper is substrate capacitance modeling for MOSFET-based RF switches on high-ohmic silicon substrates. Microstrip line computational models are applied for calculating the capacitance. It is proposed to use inverted microstrip line model for the flip-chip IC mounting configuration. The model-to-hardware correlation has been demonstrated on a prototype switch IC fabricated in a dedicated 130 nm bulk-CMOS technology. The calculated switch RF breakdown voltages (serving as an indicator for the substrate capacitance) of 56 V and 54.8 V was measured to be 55.4 V and 51.4 V for the wire-bonded and flip-chip ICs respectively.