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 c apacitors 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. % Z r indicates increases in the coordination of Zr to O atoms from 4 to approx imately 8 with increasing Zr content. The major contributions to enhancemen ts in k in these low Zr(Hf) content alloys are explained by a transverse in frared effective charge that scales inversely with increasing Zr-O bond coo rdination. (C) 2000 American Institute of Physics. [S0003-6951(00)01344-9].