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Driving force of oxygen-ion migration across high-k/SiO2 interface

We clarified the mechanism of oxygen (O−)-ion migration at a high-k/SiO2 interface, which is a possible origin of the flat-band voltage shift in metal/high-k gate stacks. The oxygen density difference accommodation model was reproduced by a molecular dynamics simulation of an Al2O3/SiO2 structure, in which O− ions migrate from the higher oxygen density side to the lower one. We determined that the driving force of the O−-ion migration is the short-range repulsion between ionic cores. The repulsive force is greater in materials with a higher oxygen density, pushing O− ions to the lower oxygen density side.