Dielectric Characteristics of Double Layer Structure of Extremely Thin Ta2 O 5 / SiO2 on Si

Abstract

The chemical structure and dielectric characteristics are investigated for amorphous tantalum pentoxide (Ta20.0 films 6-40 nm thick deposited on Si by reactive sputtering. An x-ray photospectroscopy study shows that a thin SiO~ layer grows at the Ta2Os/Si interface during the deposition. Clear boundaries between the Ta20~, SiO2, and silicon substrate are observed using a cross-sectional transmission electron microscope picture. The measured dielectric constant decreases as the Ta205 film thickness decreases. This is explained by assuming that the SiO2 thickness at the interface is 2.4 nm. The product of this dielectric constant and the electric field at a leakage current of 10 -2 A/cm 2 for the double layers decreases. It goes from 104 to 36 MV/cm as the Ta~O.~ film thickness decreases over a thickness range of about 10-40 nm. However, it remains constant about 10 nm and below. These phenomena are explained by assuming that the leakage current through the Ta20.~ film is limited by bulk limited conduction for films whose thickness exceeds 10 nm. On the other hand, in films tess than 10 nm thick, either direct tunneling or Fowler-Nordheim conduction begins. This conduction is limited by electron injection into the SiO~ at the interface from the Si substrate.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 137.222.24.34 Downloaded on 2015-03-17 to IP Vol. 134, No. 2 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 137.222.24.34 Downloaded on 2015-03-17 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 137.222.24.34 Downloaded on 2015-03-17 to IP

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