Ti gate compatible with atomic-layer-deposited HfO2 for n-type metal-oxide-semiconductor devices

Abstract

The electrical characteristics were evaluated for the metal-oxide-semiconductor (MOS) devices with Ti and Pt gates on the atomic-layer-deposited (ALD) HfO2. The equivalent oxide thickness (EOT) of the Ti gate is shown to be nearly the same as that of the Pt gate, which means that a negligible chemical reaction occurs between the gate and dielectric. The values of the effective metal work function (Φm,eff), extracted from the conventional relations of flatband voltage versus EOT, were ∼4.2eV for Ti and ∼5.4eV for Pt, respectively. However, somewhat higher values of Φm,eff were extracted by considering the existence of an interfacial layer and the high negative charge at an interface between HfO2 and interfacial layer. The exact values of Φm,eff were ∼4.37eV for Ti and ∼5.51eV for Pt, respectively. Therefore, the Ti gate is compatible with ALD-HfO2 and can be a candidate for n-type MOS devices.