부산대학교 도서관

This research explored the impact of stacked work function metals (WFM) on gate stress reliability in n- and p-FinFETs. A study of four different gate stacks, utilizing p-type WFM (TiN) and n-type WFM (TiAl) in tri-gate FinFETs, resulted in four threshold voltages ( ${V}_{\text {t}}{)}$ ranging from lowest to highest: n-type low ${V}_{\text {t}}$ , n-type standard ${V}_{\text {t}}$ , p-type standard ${V}_{\text {t}}$ , and p-type low ${V}_{\text {t}}$ . The research revealed that devices with the lowest (highest) WFM on the gates displayed the highest ${V}_{\text {t}}$ and subthreshold swing (S.S.) degradation under positive (negative) gate stress. Both energy diagram-based electric field ( ${E}{)}$ simulations and device simulations confirmed the measurement results. Moreover, the study demonstrated that the ${E}$ monotonically decreased/increased with the increase of work function only when the absolute value of the gate voltage ( $\vert {V}_{\text {G}}\vert {)}$ was sufficiently large, while the ${E}$ reversed when the $\vert {V}_{\text {G}}\vert $ became small. The work function of the reversing ${E}$ in the un-doped state approached the mid-gap energy level of silicon, as the $\vert {V}_{\text {G}}\vert $ reached its minimum.