Thermal stability and electronic structure of hafnium and zirconium oxide films for nanoscale MOS device applications

To maintain proper control of the small-sized MOS transistor, the thickness of conventional silicon gate oxide has been scaled down to its technological limit and is now very close to its theoretical limit. Searching for gate dielectrics with higher dielectric constant (high-k), which allows larger physical thickness, is indispensable. However, because the high-K materials are proposed for the extreme nanoscale applications, the requirements for the material properties are crucial. Particularly, the high-K/Si interface, which governs the device properties and reliabilities, has to be investigated in great detail. Unfortunately, our understanding of this interface and even the knowledge of its material properties are still very primitive. This paper reviews the recent progress in studying the material thermal properties and electronic structure of the hafnium and zirconium oxide, which are considered as the most promising replacements for future gate dielectric material.