A Degradation Mechanism for Threshold Voltage Asymmetry and Subthreshold Leakage Slope with Reliability Implications

Degradation in subthreshold leakage slope and increased threshold voltage asymmetry, between forward and reverse directions, could occur in short-channel FET devices when operating, even for a very short, at sustaining conditions. With this degradation, devices become more susceptible to channel and substrate hot electron effects. Failure analysis of devices that exhibited these electrical characteristics revealed the presence of a surface defect in the channel at the junction of the diffusion being biased. The cause of this defect, the techniques used to delineate its presence and its effects on the device characteristics will be discussed.