Charge-Transfer Dipoles at the Si-SiO2 Interface and the Metal-Semiconductor Worfunction Difference In Mos Devices.

Abstract

AbstractThe magnitude of the dipole moment at the Si-SiO2 interface resulting from partial charge transfer that takes place upon the formation of interface bonds has been calculated. The charge transfer occurs because of the difference in electronegativity between silicon atoms and SiO2 molecules which are present across the interface. Results obtained for (100) and (111) silicon substrates indicate that the magnitude of the interface dipole moment is dependent on substrate orientation and the interface chemistry. Dipole moments at the Si-SiO2 and gate-SiO2 interfaces should be included in the definition of the flatband voltage VFB of MOS structures. CV-based measurements of the metal-semiconductor workfunction difference φms on (100) and (111) silicon oxidized in dry oxygen and metallized with Al agree with the predictions of this model. Other types of interface dipoles and their processing dependence are briefly discussed.