Novel Fabrication Process for HfO2 Thin Film for Gate Dielectric

Abstract

A novel process for fabricating a high-k dielectric/Si structure is proposed. The structure is fabricated by ultrahigh vacuum (UHV) sputtering of Hf metal followed by postannealing in atmospheric oxygen ambient. In the fabrication of structures by this method, an interfacial layer such as SiO2 is scarcely formed because the Si surface is already covered with Hf metal from UHV sputtering, before heating in oxygen ambient. Also a postoxidation condition is set up so that the metal Hf, but not the substrate Si, is oxidized completely. Consequently, the HfO2/Si structure was fabricated with an interfacial layer thickness of as low as 0.2 nm. In addition, thermal stability of the HfO2 film fabricated by this method was maintained up to 800°C for 30 min, which is a standard thermal budget for the impurity activation process. These experimental facts show that this novel process is effective for fabricating the high-k dielectric/Si stacked structure with ultrasmall equivalent oxide thickness (EOT) for the next-generation metal-oxide-semiconductor field effect transistor (MOSFET).