Oxides with higher dielectric constants are required to act as gate dielectrics for future generations of electronic devices. The electronic structure and band offsets of the oxides on Si have been calculated for many candidate gate oxides using the local density formalism pseudopotential method. The predicted conduction band offsets are similar to those found earlier using the tight-binding method, and where available, with experimental values found by photoemission and internal photoemission. The oxides which are acceptable as gate oxides in terms of their band offsets are ZrO2, HfO2, La2O3, Y2O3, Al2O3, silicates such as ZrSiO4 and HfSiO4 and aluminates such as LaAlO3.
Interstitial hydrogen is calculated to act as a shallow donor in the candidate high dielectric constant (k) gate oxides ZrO2, HfO2, La2O3, Y2O3, TiO2, SrTiO3, and LaAlO3 but is deep in the oxides SiO2, Al2O3, ZrSiO4, HfSiO4, and SrZrO3. This may account for the change of sign of fixed charge in oxides, from negative in Al2O3 to positive in HfO2.
We find that addition of nitrogen to high-dielectric-constant gate oxides such as HfO2, La2O3, and silicates adds gap states up to 1.2 eV above their valence-band edge. This reduces the valence-band offset, but not by enough to reduce the hole injection barrier to unsafe levels. Nitrogen also leads to a decrease in average atomic coordination, which may help to increase their resistance to crystallization and ability to withstand high temperature processing.
New oxides with high dielectric constant are required for gate oxides. ZrO2 is a typical example with ionic bonding. We give the rules for bonding at interfaces between Si and ionic oxides, to satisfy valence requirements and give an insulating interface. Total energies and band offsets are calculated for various (100)Si:ZrO(2) and HfO2 interface structures. The oxygen-terminated interface is found to be favored for devices, because it has no gap states and has a band offset which is rather independent of interfacial bonding.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.