ScNx gate on atomic layer deposited HfO2 and effect of high-pressure wet post deposition annealing

For nMOS devices with HfO₂, a metal gate with a very low workfunction is necessary. In this letter, the effective workfunction (Φ_m,eff) values of ScN_x gates on both SiO₂ and atomic layer deposited (ALD) HfO₂ are evaluated. The ScN_x/SiO₂ samples have a wide range of Φ_m,eff values from ∼ 3.9 to ∼ 4.7 eV, and nMOS-compatible Φ_m,eff values can be obtained. However, the ScN_x gates on conventional post deposition-annealed HfO₂ show a relatively narrow range of Φ_m,eff values from ∼ 4.5 to ∼ 4.8 eV, and nMOS-compatible Φ_m,eff values cannot be obtained due to the Fermi-level pinning (FLP) effect. Using high-pressure wet post deposition annealing, we could dramatically reduce the extrinsic FLP. The Φ_m,eff value of ∼ 4.2 eV was obtained for the ScN_x gate on the wet-treated HfO₂. Therefore, ScN_x metal gate is a good candidate for nMOS devices with ALD HfO₂.