Oxidation mechanism proceeding at local/entire area of hafnium absorbed Si(111)

Kakiuchi, Takuhiro*; Tsuda, Yasutaka   ; Yoshigoe, Akitaka 

HfO has attracted much attention as a high-k gate dielectric material for Si semiconductor devices. In this study, oxidation by O gas exposure (Et: 0.03 eV) and supersonic O molecular beams (Et: 0.39, 2.2 eV) on Si(111) with different amounts of Hf adsorbed at about 0.5 and 2.0 ML were observed and analyzed by Hf4f, Si2p and O1s photoelectron spectroscopy. At low coverage of 0.5 ML, Hf adsorbs on rest-atoms and adatoms on Si(111)-77 to form a peculiar local structure (hexagonal structure), around which oxidation proceeds only to Hf silicate. At 2.0 ML, on the other hand, the oxidation reaction proceeds rapidly over the entire surface metal Hf layer and is considered to produce up to Hf silicate.