Improved method for evaluating hot-carrier aging in p-channel MOSFET's

A constant gate current stress method for characterizing the hot-carrier aging effect in p-channel MOSFETs is described. Unlike the conventional constant voltage stress method, the gate current is monitored and maintained constant during the stress by adjusting the drain voltage at short time intervals. This approach ensures a constant electron injection rate into the oxide during the stress period. It eliminates the degradation saturation effect. In order to compare hot-carrier sensitivities, it is desirable to be able to correlate the devices with different gate lengths from the same process technology into one straight line. This has been achieved by utilizing the substrate current extrapolated at lifetime, I/sub sub/(t= tau ), rather than the initial substrate current, I/sub sub/(0), as the hot-carrier generation indicator. Therefore, by combining the constant gate current stress test method with the modified lifetime extrapolation procedure, it also becomes possible to compare the hot-carrier sensitivities of different process technologies.<
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