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Journal Articles

Oxidation mechanisms of hafnium overlayers deposited on an Si(111) substrate

Kakiuchi, Takuhiro*; Matoba, Tomoki*; Koyama, Daisuke*; Yamamoto, Yuki*; Yoshigoe, Akitaka

Langmuir, 38(8), p.2642 - 2650, 2022/03

https://doi.org/10.1021/acs.langmuir.1c02711

Times Cited Count：1 Percentile：13.58(Chemistry, Multidisciplinary)

0xidation processes at the interface and the surface of Si(111) substrate with thin Hf films were studied using photoelectron spectroscopy in conjunction with supersonic oxygen molecular beams (SOMB). The oxidation starts at the outermost Hf layers and produces stoichiometric HfO $_{2}$ . Hf silicates (Hf-O-Si configuration) were generated in the vicinity of the HfO $_{2}$ /Si interface in the case of the irradiation of 2.2 eV SOMB. The oxidation of the Si substrate takes place to generate SiO $_{2}$ compounds. Si atoms were emitted from the SiO $_{2}$ /Si interface region underneath the HfO $_{2}$ overlayers to release the stress generated within the strained Si layers. The emitted Si atoms can pass through the HfO $_{2}$ overlayers and react with the impinging O $_{2}$ gas.

Oral presentation

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

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

no journal, ,

HfO $_{2}$ has attracted much attention as a high-k gate dielectric material for Si semiconductor devices. In this study, oxidation by O $_{2}$ gas exposure (Et: 0.03 eV) and supersonic O $_{2}$ 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 $^{3+}$ 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 $^{4+}$ silicate.