Composition-dependent crystallization of alternative gate dielectrics

We have investigated the crystallization of amorphous oxides that are considered likely candidates to replace amorphous SiO2 as the gate dielectric in advanced field-effect transistors. To avoid crystallization, the mole fraction of main-group oxide in the Zr-Si-O, Zr-Al-O, and Hf-Si-O systems must be greater than 83%, 65%, and 78%, respectively, leading to a maximum useful dielectric constant of only 6.9, 12.7, and 6.6, respectively. We conclude that the silicate systems are not likely to be useful as replacements for SiO2, while aluminates are more promising. (C) 2003 American Institute of Physics.