Statistics of progressive breakdown in ultra-thin oxides

Abstract

Electrical breakdown manifests itself in ultra-thin oxides by a gradual and systematic rise in gate leakage current. On average, this progressive breakdown is shown to increase the gate leakage exponentially with time, with the time constant exponentially dependent on the gate voltage. Because thin oxides do not instantaneously short at the commencement of breakdown, the definition of oxide failure may be altered from the first jump in gate current to the leakage value that disrupts circuit operation. Depending on the ratio of the defect production rate to the defect growth rate, multiple breakdowns may form in a single device. A Monte Carlo simulator combines these results and calculates the oxide failure distribution with failure defined by a leakage level. The simulations reveal that updating the definition of oxide failure increases the projected reliability by many orders of magnitude.