Ti gate compatible with atomic-layer-deposited HfO_2 for n-type metal-oxide-semiconductor devices

摘要

The electrical characteristics were evaluated for the metal-oxide-semiconductor (MOS) devices with Ti and Pt gates on the atomic-layer-deposited (ALD) HfO_2. 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 (Φ_(m,eff)), extracted from the conventional relations of flatband voltage versus EOT, were ～4.2 eV for Ti and ～5.4 eV for Pt, respectively. However, somewhat higher values of Φ_(m,eff) were extracted by considering the existence of an interfacial layer and the high negative charge at an interface between HfO_2 and interfacial layer. The exact values of Φ_(m,eff) were ～4.37 eV for Ti and ～5.51 eV for Pt, respectively. Therefore, the Ti gate is compatible with ALD-HfO_2 and can be a candidate for n-type MOS devices.