Characterization of Fully Embedded RF Inductors in Organic SOP Technology

Abstract

In this paper, we investigate fully embedded circular spiral inductors in multilayered organic packaging substrate for radio-frequency (RF) and microwave applications. The proposed spiral inductors are designed with circular geometry to improve their quality factors and the vertically stacked geometry is utilized to reduce the component area resulting in the increment of packaging density. And also the embedded circular spiral inductors are designed with conductor backed coplanar waveguide (CBCPW) structures for utilizing them directly for compact RF modules and systems. They are evaluated and optimized by varying their geometry parameters such as a number of turns, inner diameter, and embedded layer. These embedded inductors are accurately designed and analyzed by 3-D EM simulation and equivalent circuit modeling. The planar circular spiral two-turn inductor has inductance of 8.6 nH and maximum quality factor of 67 at 1 GHz. The vertically stacked circular spiral two-turn inductor has inductance of 10.2 nH and maximum quality factor of 66 at 1 GHz. The size of the vertically stacked inductor is approximately 70% of the planar one. The measured performance characteristics are well matched with the 3-D EM simulated ones.Index Terms-Circular spiral, embedded, inductor, organic substrate, packaging density, quality factor, stacked spiral, system on packaging (SOP).