Change in Admittance of HfO2 Metal-Insulator-Metal (MIM) Capacitors after dc Bias Stress

We report on the admittance of Au/HfO2/TiN MIM capacitors which have been subjected to a dc bias stress (3 V for films with an equivalent oxide thickness of 3.25 nm). Different stress conditions are applied, and the resulting capacitance and ac conductance are measured as a function of frequency. Though charge trapping and dc leakage current are observed under short stress time (1500 s), after bias removal the ac admittance is not affected. This underlies the ability of the capacitor to recover from stress. After longer stress times (10000 s), the capacitance decreases, achieving negative values at very low frequencies. Such a degradation is ascribed to important charge trapping. (C) 2013 The Electrochemical Society. All rights reserved.