Effect of La2O3 Capping Layer Thickness on Hot-Carrier Degradation of n-Channel Metal--Oxide--Semiconductor Field-Effect Transistors with High-$k$/Metal Gate Stacks

The effect of La 2 O 3 capping layer thickness on the hot-carrier degradation of n-channel metal--oxide--semiconductor field-effect transistors (n-MOSFETs) with high-$k$/metal gate stacks is investigated. The hot-carrier degradation is monitored by measuring the threshold voltage $V_{\text{th}}$, transconductance $g_{\text{m}}$, and subthreshold slope $\mathit{SS}$. As the thickness of the La 2 O 3 layer increases, $V_{\text{th}}$ degradation is enhanced regardless of whether the La 2 O 3 layer is deposited above or below the HfSiO layer. The generation of interface traps induced by hot-carrier stress is intensified with an increase in the bottom capping layer thickness. On the other hand, the generation of oxide traps induced by hot-carrier stress is intensified with an increase in the top capping layer thickness.