Competing Degradation Mechanisms in Short-Channel Transistors Under Channel Hot-Carrier Stress at Elevated Temperatures

The temperature dependence of channel hot-carrier (CHC) degradation in n-MOS transistors with high-k dielectrics has been studied. The analysis starts from the most damaging CHC stress conditions at room temperature (V _G = V _D/2 for long channels and V _G = V _D for short channels). We find that, for long-channel transistors, the CHC degradation decreases at high temperature, while for short-channel transistors, an increase is observed. In this paper, a new picture to explain the observed increment of CHC damage with temperature for short-channel transistors with high-k dielectric is presented. We demonstrate that the total CHC degradation consists of two components: the classical CHC damage located at the drain side and the degradation produced by the voltage drop over the gate dielectric, which can be considered a positive bias temperature instability (PBTI) effect. Particularly for short transistors stressed at high temperatures, this PBTI component dominates the total CHC degradation.