Lifetime-limited current in Cu-gate metal-oxide-semiconductor capacitors subjected to bias thermal stress

Increased oxide conductance is widely observed in Cu-gate metal-oxide-semiconductor capacitors subjected to bias thermal stress. Prior to oxide breakdown, the increased conductivity enables the leakage of minority carriers from the Si inversion layer, resulting in permanent deep-depletion capacitance-voltage characteristics. Furthermore, under such conditions the minority-carrier generation statistics in the Si cannot be calculated from capacitance-time measurements. To quantify this phenomenon, a model is proposed, which relates oxide leakage current with the rate at which minority-charge carriers are generated in the depleted Si. Using this model, the minority-carrier generation statistics can be calculated from current and capacitance measurements. We show that the proposed model fits well with the experimental data and that the calculated generation parameters are within the expected range for Cu-affected Si.