Spectroscopic and electrical properties of ultrathin SiO2 layers formed with nitric acid

Autor: Hitoo Iwasa, Hikaru Kobayashi, T. Kobayashi, Masao Takahashi, Asuha
Rok vydání: 2003
Předmět:
Zdroj: Surface Science. 547:275-283
ISSN: 0039-6028
DOI: 10.1016/j.susc.2003.09.016
Popis: Spectroscopic and electrical properties of ultrathin silicon dioxide (SiO2) layers formed with nitric acid have been investigated. The leakage current density of the as-grown SiO2 layers of 1.3 nm thickness is high. The leakage current density is greatly decreased by post-oxidation annealing (POA) treatment at 900 � C in nitrogen, and consequently it becomes lower than those for thermally grown SiO2 layers with the same thickness. X-ray photoelectron spectroscopy measurements show that high density suboxide species are present before POA and they are markedly decreased by POA. Fourier transformed infrared absorption measurements show that water and silanol group are present in the SiO2 layers before POA but they are removed almost completely by POA above 800 � C. The atomic density of the as-grown chemical SiO2 layers is 4% lower than that of bulk SiO2 layers, while it becomes 12% higher after POA. It is concluded that the high atomic density results from the desorption of water and OH species, and oxidation of the suboxide species, both resulting in the formation of SiO2. The valence band discontinuity energy at the Si/SiO2 interface increases from 4.1 to 4.6 eV by POA at 900 � C. The high atomic density enlarges the SiO2 band-gap energy, resulting in the increase in the band discontinuity energy. The decrease in the leakage current density by POA is attributed to (i) a reduction in the tunneling probability of charge carriers through SiO2 by the enlargement of the band discontinuity energy, (ii) elimi- nation of trap states in SiO2, and (iii) elimination of interface states. � 2003 Elsevier B.V. All rights reserved.
Databáze: OpenAIRE
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