Using ab initio density functional calculations, a study was made of the implications of film growth kinetics for the structure and defects in the HfO2/Si(001) interface region. A simplified model was introduced for atomic layer deposition, with HfCl4 as a metal precursor and H2O as the oxidant. This model suggested that the initial interface growth resulted in a typically less than 1 monolayer of Hf in the first metallic layer. The O coordination at the interface was either two (one Si and one Hf atom) or three (two Hf and one Si atoms). This partially supported kinetically motivated interface models, but contrasted with previously suggested epitaxially motivated models. Further calculations showed that the O vacancy formation energy at the Si-O-Hf sites was about 1eV lower than that in bulk HfO2. This made the Si-Hf bond a likely interface defect; predicted to be a shallow hole trap. Calculations also predicted interstitial O migration from HfO2 into the Si substrate; resulting in the formation of the SiOx interface layer.

Ab initio Modeling of Structure and Defects at the HfO2/Si Interface. J.L.Gavartin, L.Fonseca, G.Bersuker, A.L.Shluger: Microelectronic Engineering, 2005, 80, 412-5