Voltage dependence of hard breakdown growth and the reliability implication in thin devices

Hard breakdown (HBD) is shown to be a gradual process with the gate current increasing at a predictable rate exponentially dependent on the instantaneous stress voltage and oxide thickness. This is contrary to conventional wisdom that maintains that HBD is a fast thermally driven process. The HBD degradation rate (DR) for a 1.5 nm oxide scales from 1 mA/s at 4 V to 1 nA/s at 2 V, extrapolating to 10 fA/s at use voltage. Adding the HBD evolution time to the standard time-to-breakdown potentially reduces the projected fail rate of gate dielectrics by orders of magnitude.