Q-Factor Behavior Study of On-Chip Inductors Using Transmission-Line Model

This paper presents a novel transmission-line model for on-chip inductors to derive their quality (Q) factors in terms of the well-known transmission-line parameters in closed forms. The derived formulas are general and suitable for all kinds of on-chip inductors when used to account for the frequency dependence of Q factors. The presented formulas can also uniquely distinguish the improvement in Q-factor frequency responses between the reduction of conductor loss and dielectric loss. The dielectric loss mainly includes eddy- current loss and substrate-leakage loss. Several 90-nm RF- CMOS inductors have been studied for their Q-factor behavior under different design configurations and process variations.