  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.
