RF Characteristics of a high-performance, 10-fF/μm2 capacitor in a deep trench

We report the properties of a novel polysilicon-insulator-polysilicon trench capacitor with a 380-/spl Aring/ Si₃N₄ dielectric that is designed and fabricated for high-frequency bypass and decoupling applications. The capacitor has a specific capacitance as high as 10 fF/μm² 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 μ is defined as the ratio of the imaginary parts of Y/sub 11/ and -Y/sub 21/ at low frequency. The values of μ and, consequently, R/sub sub/ are extracted from fitting the measured S-parameter data, and the layout dependence of μ and R/sub sub/ is also explained by the model.