Precision high-frequency capacitor formed on semiconductor substrate

Abstract

A method of fabricating a capacitor in a semiconductor substrate. The semiconductor substrate is doped to have a low resistivity. A second electrode, insulated from a first electrode, is formed over a front side surface and connected by a metal-filled via to the back side surface. The via may be omitted and the second electrode may be in electrical contact with the substrate or may be formed on top of the dielectric layer, yielding a pair of series-connected capacitors. ESD protection for the capacitor is provided by a pair of oppositely-directed diodes formed in the substrate connected in parallel with the capacitor. Capacitance is increased while maintaining a low effective series resistance. Electrodes include a plurality of fingers, which are interdigitated with the fingers of other electrode. The capacitor is fabricated in a wafer-scale process with other capacitors, where capacitors are separated from each other by a dicing technique.