QBD (electronics)

QBD is the term applied to the charge-to-breakdown measurement of a device and is a method used to determine reliability of gate oxides in MOS devices.

Voltage is applied to the MOS structure to force a controlled current through the oxide, i.e. to inject a controlled amount of charge into the oxide. By measuring the time after which voltage drops to zero (oxide breakdown occurs) and knowing injected current, the charge needed to break the oxide is determined.

This accumulated oxide charge is defined as:

$Q\_\{bd\}=int\_\{0\}^\{t\_\{bd\; i(t),\; dt$

where $t\_\{bd\}$ is the measurement time at the step just prior to breakdown.