It is a standard destructive test method used to determine the quality of gate oxides in MOS devices.
As a measure of oxide quality, QBD can also be a useful predictor of product reliability under specified electrical stress conditions.
By measuring the time after which the measured voltage drops towards zero (when electrical breakdown occurs) and integrating the injected current over time, the charge needed to break the gate oxide is determined.
One of the defined criteria is the change of logarithmic current slope between successive voltage steps.
The cumulative distribution of measured QBD is commonly analysed using a Weibull chart.