Characterization and modeling of silicon integrated spiral inductors for high-frequency applications

Abstract

This paper presents the characterization and modeling of 0.3-to 0.8-nH radial patterned ground shield circular inductors fabricated in a silicon bipolar technology for RF applications. An extensive validation of measurement accuracy is first addressed taking into account both calibration and de-embedding issues. A novel five-step de-embedding technique is also proposed to improve the accuracy of small inductor measurements. The accuracy of de-embedded experimental data in the range 0.3-0.8 nH is demonstrated by comparing the measured low-frequency inductance with electromagnetic simulations of a large set of inductors. Based on both electromagnetic simulations and experimental measurements, the well-known current sheet expression for circular spirals is revised and modified to improve its accuracy at lower inductance values. The proposed expression is also extended to inductors with polygonal geometries showing significant improvements with respect to the state-of-the-art. Finally, the original and modified expressions are employed in a lumped scalable model for silicon spiral inductors. Comparisons with measured data revealed that the modified expression allows error reductions as large as 20% with respect to the original one, on both inductance and quality factor simulations.

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