Hydrogen Barrier Layer Against Silicon Oxidation during Atomic Layer Deposition of Al2 O3 and Hf O2

Abstract

Growth at moderate temperatures, below ∼100°C, is shown to prevent interfacial silicon oxidation during atomic layer deposition of high-permittivity (high- κ) gate dielectrics on hydrogen-terminated Si(100). Trimethylaluminum, employed for aluminum oxide growth, leaves the hydrogen layer completely intact. Tetrakis(ethylmethylamido)hafnium partially scavenges the hydrogen layer during hafnium oxide nucleation, resulting in an interface composed of H-terminated silicon atoms and Si-O-Hf bridges. In both cases, high- κ dielectrics are grown without formation of interfacial Si O2. Once grown at low temperatures, subnanometer Al2 O3 layers effectively prevent interfacial Si O2 formation during subsequent growth at higher temperatures required for optimum high- κ quality. This two-step deposition scheme may thereby be useful for gate-stack scaling. © 2007 The Electrochemical Society.