Material dependence of hydrogen diffusion: implications for NBTI degradation

Negative bias temperature instability (NBTI) is known to exhibit significant recovery upon removal of the gate voltage. The process dependence of this recovery behavior is studied by using the time slope (n) as the monitor. We observe a systematic variation of n with oxide thickness, nitrogen concentration, and fluorine implantation. Incorporation of the material dependence of the diffusivity within the reaction-diffusion (R-D) framework captures the observed trends. The consequences of this modification are (a) diffusion limitation is shown to arise from diffusion in poly-Si, rather than oxide, (b) a plausible explanation for low-voltage stress induced leakage current (LV-SILC) naturally appears. Important findings are (a) NBTI degradation remains significant at high frequencies, (b) numerical simulations at moderate frequencies can be used to predict circuit impact in the GHz regime, (c) high frequency operation can be modeled as a lower effective DC stress.