High Q backside micromachined CMOS inductors

Spiral inductors that are fabricated through a CMOS process, are micromachined by using a new post-processing procedure. In this new technique, the inductors are supported mechanically prior to etching with a low-loss host substrate, and the silicon substrate is selectively etched from the backside. A scalable physical model for such inductors is developed. The results from the model are in good agreement with the measurements. Significant performance improvements are achieved without compromising the mechanical robustness of the fully integrated inductors. By using a 1.2 mu m CMOS technology, a quality factor of 10.5 is measured at 4.6 GHz for 8.9 inductor.