PMOSFET hot-carrier damage: oxide charge and interface states

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The hot-carrier degradation mechanism in PMOSFETs (p-channel metal-oxide-semiconductor field-effect transistors) is studied for three transistor types over ten orders of magnitude in time. The authors observe oxide charge and interface states separately by charge pumping. Degradation for various gate lengths at many gate and drain voltages is measured and interpreted consistently. Negative oxide charge and interface states are generated by electrons near the drain. This charge attracts an inversion layer that extends the drain and reduces the effective transistor length logarithmically in time, simultaneously preventing degradation of the transistor operation by the generated interface states. However, holes may generate interface states outside the drain extension, decreasing the transconductance with a power of time.