Channel Hot-Carrier Degradation in Short-Channel Transistors With High- k/Metal Gate Stacks

Channel hot-carrier (CHC) degradation in nMOS transistors is studied for different SiO2/HfSiON dielectric stacks and compared to SiO2. We show that, independent of the gate dielectric, in short-channel transistors, the substrate current peak (used as a measure for the highest degradation) is at VG= VD, whereas for longer channels, the maximum peak is near VG= VD/2. We demonstrate that this shift in the most damaging CHC condition is not caused by the presence of the high- k layer but by short-channel effects. Furthermore, the CHC lifetime of short-channel transistors was evaluated at the most damaging condition VG= VD, revealing sufficient reliability and even larger operating voltages for the high-k stacks than for the SiO2reference.