Influence of the diffusion geometry on PN Integrated Varactors

Abstract

In this work, four different structures based on PN junction are studied. These structures are based on changing the geometry of the p+ diffusion. The designed and fabricated devices will be used like integrated varactors in radiofrequency applications. The measures have been made at frequencies since 500 MHz to 10 GHz, and the influence that diffusion geometry has in the capacitance (C), the quality factor (Q) and the tuning range (TR) have been studied. The pn varactors have been simulated with Taurus Device and have been fabricated in a 0.35um SiGe standard process. In order to obtain better benefits of the varactors, the p(+) and n(+) diffusion geometries have been modified. This way, novel structures called crosses, fingers, donuts, and bars have been designed and fabricated. The results of the tuning range have been obtained superior to 40%.