Microscopic model for enhanced dielectric constants in low concentration SiO2-rich noncrystalline Zr and Hf silicate alloys

Dielectric constants, k, of Zr(Hf) silicate alloy gate dielectrics obtained from analysis of capacitance–voltage curves of metal–oxide–semiconductor capacitors with 3–6 at. % Zr(Hf) are significantly larger than estimates of k based on linear extrapolations between SiO2 and compound silicates, Zr(Hf)SiO4. Analysis of infrared spectra of Zr silicate alloys with 3–16 at. % Zr indicates increases in the coordination of Zr to O atoms from 4 to approximately 8 with increasing Zr content. The major contributions to enhancements in k in these low Zr(Hf) content alloys are explained by a transverse infrared effective charge that scales inversely with increasing Zr–O bond coordination.