A Scalable Model of On-Chip Inductor Including Tunable Dummy Metal Density Factor

Abstract

Because of the metal density requirement in the advanced CMOS processes, dummy metal fills (DMFs) are unavoidable. The DMFs degrade the performance of the onchip inductors, especially for the ones in the microwave and millimeter-wave circuits. This paper analyzes the impact of the floating DMFs and proposes a scalable double-π inductor model including a tunable dummy metal density factor. The metal density factor can be integrated into the process design kit and determined by the designers to pass the design rule check. The proposed model predicts the decrease in the quality factor (Q) and self-resonance frequency ( fsr) with the density of DMFs increasing accurately. Furthermore, a fully automatic model extraction method based on the genetic algorithm is presented, which increases the accuracy of models. Inductors with DMFs of different densities are fabricated in a standard 180-nm CMOS technology. Then, the parameters of the inductors' models are extracted to verify the idea. The models' calculation results are compared with the measurement results up to 67 GHz.