Characterization of Transistors for Silicon Integrated Chopper Applications at Sub-THz Frequencies

Abstract

Two devices, a SiGe BiCMOS MOSFET and a SiGe HBT, were characterized through on-wafer measurements in the 220–500 GHz range. The results showed that the PDK model of the MOSFET did not accurately represent the device. Conventional open–short de-embedding was found to lose accuracy at sub-THz frequencies due to its inherent lumped-element approximation. To address this limitation, an improved de-embedding method was developed by estimating a correction matrix A′ using transmission-line equivalent circuits, achieving up to 15.6 dB improvement in S11 and S22 for an HBT interconnect in simulation compared to the classical approach. The characterized MOSFET was used to simulate the integrated chopper transmissivity, which closely matched over-the-air measurements. The HBT characterization showed better agreement with the PDK, but the higher characterized capacitance resulted in reduced chopper performance.