Hot-carrier-induced alterations of MOSFET capacitances: a quantitative monitor for electrical degradation

In this paper, combined gate-to-channel (C_GSD) and gate-to-bulk (C_GB) capacitance measurements are used in order to extract quantitative information about hot-carrier degradation in MOS transistors. An analytical model, explaining the results of accelerated degradation experiments, is presented to establish a simple relationship between C_GSD and C_GB changes and the stress-induced charges Q_ox and Q_it trapped in the oxide or in interface states, respectively. A method, validated by means of two-dimensional (2-D) numerical simulations, is proposed to determine Q_ox and Q_it directly from the measured capacitances, and is applied to experimental data. The new technique considerably improves the capabilities of previous capacitive methods because it can yield a quantitative determination of Q_ox and Q_it