Physical Mechanism Underlying the Time Exponent Shift in the Ultra-fast NBTI of High-k/Metal gated p-CMOSFETs

In this study, ultra-fast methods were used to measure the threshold voltage shift $(\Delta\mathrm{V}_{\mathrm{T}})$ of the negative bias temperature instability (NBTI) in p-channel complementary metal oxide semiconductor field effect transistors (p-CMOSFETs) with a high-klmetal gate (HK/MG) stack. The voltage (Vg,str) and temperature (T) dependence of the NBTI time exponent (n) were studied under a wide range of stress conditions, and the results demonstrated a strong T dependence of n above room temperature (RT) and that the field reduction effect played an important role in determining the dependence of $n$ on Vg,str and T. With the direct current current-voltage (DCIV) method, the similarity of n, activation energy (EA) and voltage acceleration factor $(\Gamma)$ between the trap generation $(\Delta \mathrm{N}_{\mathrm{T}})$ and $\Delta \mathrm{V}_{\mathrm{T}}$ indicates that $\Delta \mathrm{N}_{\mathrm{T}}$ is the dominant subcomponent at higher values of T. The impact of the field reduction effect on the time exponents of $\Delta\mathrm{V}_{\mathrm{T}}$ and $\Delta\mathrm{V}_{\mathrm{T}}$, EA, and $\Gamma$ were also investigated.