CMOS varactor model extraction up to 110 GHz

This paper presents S-parameter based varactor model extraction in 90 nm CMOS process. The model has been extracted for different tuning voltages from tank circuit measurement results up to 110 GHz. Two tank circuits with different varactor sizes are realized and measured. The varactor sizes are scaled to have the resonant frequencies of the tank around 50 GHz and 60 GHz. Also, additional on-chip passive test structures have been realized and measured to extract the model of the feeding structure (probing pads and transmission line) and the inductors. Finally the modeled varactors are utilized in the simulation of the tanks. The comparison between simulation and measurement of the tank circuits showed a good accuracy validating the extracted model up to 110 GHz.