RF Characteristics of a high-performance, 10-fF//spl mu/m/sup 2/ capacitor in a deep trench

We report the properties of a novel polysilicon-insulator-polysilicon trench capacitor with a 380-/spl Aring/ Si/sub 3/N/sub 4/ dielectric that is designed and fabricated for high-frequency bypass and decoupling applications. The capacitor has a specific capacitance as high as 10 fF//spl mu/m/sup 2/ normalized to its footprint area, and a breakdown voltage greater than 15 V at room temperature. The measured S-parameters are in excellent agreement with simulations of an equivalent circuit model that includes a shunt substrate resistance to ground (R/sub sub/). A geometric factor /spl mu/ is defined as the ratio of the imaginary parts of Y/sub 11/ and -Y/sub 21/ at low frequency. The values of /spl mu/ and, consequently, R/sub sub/ are extracted from fitting the measured S-parameter data, and the layout dependence of /spl mu/ and R/sub sub/ is also explained by the model.