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 La2O3 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-th, transconductance g(m), and subthreshold slope SS. As the thickness of the La2O3 layer increases, V-th degradation is enhanced regardless of whether the La2O3 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. (C) 2012 The Japan Society of Applied Physics