Passive and Causal Modeling of 300-GHz-Band IC Capacitors Using Rational Polynomial Approximation

This research presents a method to model metal-oxide-metal (MOM) capacitors for 300-GHz band applications using rational polynomial approximation (RPA). While initial approximations often lead to negative element values due to measurement errors, the model is redefined by re-fitting with restrictions to ensure passivity and causality. This approach produces accurate equivalent circuits suitable for high-frequency simulations. The method was validated with measurement with test structure chip fabricated with 0.13 μm SiGe BiCMOS process.