Mechanism of degradation of LDD MOSFETs due to hot-electron stress

The dominant degradation mechanism in n-channel lightly doped drain (LDD) MOSFETs following hot-electron injection is identified. While there is no shift in the threshold voltage or any change in the subthreshold slope (implying no significant interface state generation), the peak value of the transconductance is found to degrade with stress time. This degradation is attributed to the increase in the source-drain series resistance, which is measured as a function of stress time. In addition, it is found that for any stress time, the measured series resistance is a strong function of the gate voltage, implying a modulation of the depletion width in the lightly doped region with change in the gate voltage.< >