Thermal self-limiting effects in the long-term AC stress on n-channel LDD MOSFETs

A model of lightly doped drain n-MOSFET degradation in drain current under long-term AC use conditions which includes a self-limiting effect in the hot-electron induced device degradation is proposed for lifetime projections. Experimental results on LDD n-MOSFETs (W=50 μm) are presented which show the maximum drain current degradation as a function of the average substrate current under the various AC stress and use conditions (f=0.4 MHz, 1 MHz, 2 MHz, and 4 MHz) for different drawn gate lengths. The maximum drain current degradations were 0.3% μA, 0.2%/μA, and 0.15%/μA of the substrate current for drawn gate lengths of 0.8 μm, 1.0 μm, and 1.5 μm, respectively, at an ambient temperature of 25°C. The proposed model also includes and predicts the strong temperature dependence