Characterization of HfO 2 /Si Exposed to Water Vapor at Room Temperature

HfO 2 -based materials are the leading candidates to replace SiO 2 as the gate dielectric in Si-based metal-oxide-semiconductor filed-effect transistors. The ubiquitous presence of water vapor in the environments to which the dielectric films are exposed (e.g. in environmental air) leads to questions about how water could affect the properties of the dielectric/Si structures. In order to investigate this topic, HfO 2 /SiO 2 /Si(001) thin film structures were exposed at room temperature to water vapor isotopically enriched in 2 H and 18 O followed by quantification and profiling of these nuclides by nuclear reaction analysis. We showed i) the formation of strongly bonded hydroxyls at the HfO 2 surface; ii) room temperature migration of oxygen and water-derived oxygenous species through the HfO 2 films, indicating that HfO 2 is a weak diffusion barrier for these oxidizing species; iii) hydrogenous, water-derived species attachment to the SiO 2 interlayer, resulting in detrimental hydrogenous defects therein. Consequences of these results to HfO 2 -based metal-oxide-semiconductor devices are discussed.