Reduction of the electron mobility in high-k MOS systems caused by remote scattering with interfacial optical phonons

The poor electron mobility presently observed in metal-insulator-semiconductor devices using high-K insulators may be due to a variety of processing and material-related issues. However, here we argue that the high-kl itself may present anintrinsic, unavoidable cause of this poor performance. Indeed, the high dielectric constant is usually accompanied by the presence of soft optical phonons. The long-range dipole field associated with the interface excitations, While small in the case of SiO2, for most high-k materials is sufficiently large to depress the effective electron mobility in the inversion layer of the Si substrate. We study the dispersion of the interfacial coupled phonon-plasmon modes, Their electron-scattering strength, and their effect on the electron mobility for Si-gate structures employing films of SiO2, Al2O3, AlN, ZrO2, HfO2, and ZrSiO4 for `SiO2-equivalent' thicknesses ranging from 5 nm to 0.5 nm.

By: Massimo V. Fischetti, Eduard Cartier, Deborah Neumayer

Published in: RC22734 in 2003


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