Model for the voltage and temperature dependence of the soft breakdown current in ultrathin gate oxides

Abstract

The voltage and temperature dependence of the soft breakdown conduction mechanism in metal-oxide-semiconductor capacitors and transistors with ultrathin dielectric layers is investigated. A physical derivation of the quantum point contact model and its parameters is presented, which incorporates the smearing of the Fermi function at the electrodes as well as the effect of thermal vibrations of the constriction’s bottleneck. The model also takes into account the boundary conditions at the two ends of the breakdown path by considering the semiconductor band bending occurring in the nondamaged surrounding device area. Good agreement between model and experimental curves is found. Because of its analytical nature, the proposed model can be implemented in circuit simulators.