Electronic structure of transition metal high-k dielectrics: Interfacial band offset energies for microelectronic devices

Transition metal silicates, (ZrO ₂ ) _x (SiO ₂ ) _1-x , have dielectric constants k > 10 that make them attractive for advanced Si devices. Band offset energies relative to Si are an important factor in determining tunneling leakage current, and internal photoemission. Studies by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and X-ray absorption spectroscopy (XAS) are combined with ab initio calculations to identify the compositional variation of the band-gap, and valence and conduction band offset energies of Zr silicate alloys with respect to Si. The minimum conduction band offset, due to Zr 4d ^* states, is shown to be independent of alloy composition, while valence band offsets decrease monotonically with increasing ZrO ₂ content. The implications of these results for direct tunneling are discussed.