Reliability physics and chemistry of thin and high-k gate oxides

The International Technology Roadmap for Semiconductors indicates that fundamental limits to downscaling will be reached by 2005. At the present time, there is therefore great technological interest in very thin SiO₂-based dielectrics as well as in "new" significantly higher dielectric constant (high-k) materials such as HfO₂, ZrO₂, and hafnium and zirconium silicates. These new oxides have considerable promise but many recent studies demonstrate that devices based upon these and other high-k oxides exhibit potentially serious reliability problems which are as yet poorly understood. This tutorial reviews recent work of a number of groups investigating dielectric charge trapping, interface traps, low channel mobilities, and other problems in new high-k oxide/silicon systems. This review ia integrated with a discussion of somewhat better understood problems in very thin SiO₂-based dielectric/silicon systems. This presentation also includes a comparison of atomic scale defects involved in hafnium oxide - hafnium silicate, zirconium oxide - zirconium silicate, and silicon dioxide based systems.