Design and Fabrication of the Suspended High-Q Spiral Inductors with X-Beams

TL;DR

This paper presents a novel high-Q spiral inductor with an air gap and X-beam structure, enhancing mechanical strength and electrical performance for CMOS applications.

Contribution

The paper introduces a new X-beam design to significantly improve mechanical strength and electrical quality factor of on-chip spiral inductors.

Findings

Maximum mechanical strength increased by over 4500 times

Quality factor improved from 5.2 to 7.3

Resonant frequency increased from 1.6 GHz to 2.1 GHz

Abstract

In this paper, deep sub-micron CMOS process compatible high Q on chip spiral inductors with air gap structure were designed and fabricated. In the design the electromagnetic were used for electrical-characteristics and maximum mechanical strength, respectively. The copper wires were capped with electroless Ni plating to prevent the copper from oxidizing. A Si3N4/ SiO2 X-beam was designed to increase the mechanical strength of the inductor in air gap. The enhancement of maximum mechanical strength of a spiral inductor with X-beams is more than 4500 times. Among these structures, the measured maximum quality factor (Q) of the suspending inductor and frequency at maximum Q are improved from 5.2 and 1.6GHz of conventional spiral inductor to 7.3 and 2.1 GHz, respectively.