Impact of Hf metal predeposition on the properties of HfO2 grown by physical and chemical vapor deposition

Electrical and microstructural properties of a hafnium oxide (HfO2) grown by physical vapor deposition (PVD) and chemical vapor deposition (CVD) onto a predeposited hafnium metal (Hf) are investigated. In PVD in an Ar/O-2 plasma atmosphere, energetic oxygen species oxidize the Si substrate through HfO2, generating a thick interfacial layer between the HfO2 and Si substrates. The interfacial layer, however, is found to be controllable to have a minimum equivalent oxide thickness (EOT) and lower leakage current by the predeposition of Hf metal due to the blocking of oxygen diffusion into the Si substrate by the oxidation of Hf metal itself. In addition to the oxygen blocking, the CVD-grown HfO2 films on the predeposited Hf metal layer are improved due to the easy dissociation of the Hf precursor on the metallic Hf layer with a shorter incubation time. The leakage current with the predeposited Hf metal is two orders of magnitude lower than that on the Si substrate, whereas the EOT and the interfacial layer thickness are invariant.