Series resistance estimation and C(V) measurements on ultra thin oxide MOS capacitors

Based on measurements on test structures with various electrical silicon oxide thicknesses (from 21 Å to 13 Å) and areas (from 27000 μm² to 2 μm²), this paper describes the effect of gate current on measured capacitance using a standard 10 kHz-to-1 MHz LCR-meter. We show that, in presence of high gate leakage, the series impedance, and also the channel debiasing, have a dramatic effect on observed C(V) curves. We also propose a segmented-MOS model, allowing discrete solution of the current continuity equation along the channel, which fits the measured C(V) and provides a solution for process monitoring (such as oxide thickness) and intrinsic capacitance determination for device modeling.