Evidence of a new degradation mechanism in high-k dielectrics at elevated temperatures

Elevated temperatures can significantly affect the driving forces of high-k degradation and breakdown. Okada et al. have proposed the generated subordinate carrier injection (GSCI) model. This model claims the universality of stress-induced leakage current (SILC) vs. hole fluence, independent of the temperature in n-channel MOSFET's with Hf and Al-based gate dielectrics. In this paper, we demonstrate that 125degC is a crucial temperature for the studied stack as an additional degradation mechanism is triggered above this temperature. Applying two material analysis techniques, SILC spectroscopy and trap spectroscopy by charge injection (TSCIS), we study the T-dependent energy spectrum of the generated defects and prove that the generation rate and the kind of participating traps in the breakdown (BD) path change at elevated temperatures.