Unloaded Q-Factors of thin film microstrip resonators in 0.18-µm CMOS for millimeter wave applications

Thin film microstrip (TFMS) lines have important applications in the design of CMOS microwave and millimeter wave circuits including on-chip filters and matching networks. In these circuits, the achievable passband insertion loss or the Q-factor of the matching networks are determined by the unloaded Q-factors of the TFMS lines. Since CMOS processes provide various possibilities for implementing TFMS lines due to the availability of multi-level metallizations, an optimum configuration needs to be determined. In this work, the two most viable configurations for the TFMS lines in a 0.18-mum CMOS process are compared by rigorous simulation and measurement of the unloaded Q-factors of the lambda/4 TFMS line resonators at 60 GHz over a broad range of characteristic impedances.