Capacitance–voltage characterization of fully silicided gated MOS capacitor

Abstract

This paper investigates the capacitance–voltage (C–V) measurement on fully silicided (FUSI) gated metal-oxide-semiconductor (MOS) capacitors and the applicability of MOS capacitor models. When the oxide leakage current of an MOS capacitor is large, two-element parallel or series model cannot be used to obtain its real C–V characteristic. A three-element model simultaneously consisting of parallel conductance and series resistance or a four-element model with further consideration of a series inductance should be used. We employed the three-element and the four-element models with the help of two-frequency technique to measure the Ni FUSI gated MOS capacitors. The results indicate that the capacitance of the MOS capacitors extracted by the three-element model still shows some frequency dispersion, while that extracted by the four-element model is close to the real capacitance, showing little frequency dispersion. The obtained capacitance can be used to calculate the dielectric thickness with quantum effect correction by NCSU C–V program. We also investigated the influence of MOS capacitor's area on the measurement accuracy. The results indicate that the decrease of capacitor area can reduce the dissipation factor and improve the measurement accuracy. As a result, the frequency dispersion of the measured capacitance is significantly reduced, and real C–V characteristic can be obtained directly by the series model. In addition, this paper investigates the quasi-static C–V measurement and the photonic high-frequency C–V measurement on Ni FUSI metal gated MOS capacitor with a thin leaky oxide. The results indicate that the large tunneling current through the gate oxide significantly perturbs the accurate measurement of the displacement current, which is essential for the quasi-static C–V measurement. On the other hand, the photonic high-frequency C–V measurement can bypass the leakage problem, and get reliable low-frequency C–V characteristic, which can be used to evaluate whether the full silicidation has completed or not, and to extract the interface trap density of the SiO2/Si interface.