Intermixing at the tantalum oxide/silicon interface in gate dielectric structures

G. B. Alers, D. J. Werder, Y. Chabal, H. C. Lu, E. P. Gusev, E. Garfunkel, T. Gustafsson, R. S. Urdahl

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Abstract

Metal oxides with high dielectric constants have the potential to extend scaling of transistor gate capacitance beyond that of ultrathin silicon dioxide. However, during deposition of most metal oxides on silicon, an interfacial region of SiOx can form that limits the specific capacitance of the gate structure. We have examined the composition of this layer using high-resolution depth profiling of medium ion energy scattering combined with infrared spectroscopy and transmission electron microscopy. We find that the interfacial region is not pure SiO2, but is a complex depth-dependent ternary oxide of Si-Tax-Oy with a dielectric constant at least twice that of pure SiO2 as inferred from electrical measurements. High-temperature annealing crystallizes the Ta2O5 film and converts the composite oxide to a more pure SiO2 layer with a lower capacitance density. Using low postanneal temperatures, a stable composite oxide structure can be obtained with good electrical properties and an effective SiO2 thickness of less than 2 nm with ∼10 nm of composite oxide.

Original languageEnglish
Pages (from-to)1517-1519
Number of pages3
JournalApplied Physics Letters
Volume73
Issue number11
DOIs
Publication statusPublished - 1998

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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    Alers, G. B., Werder, D. J., Chabal, Y., Lu, H. C., Gusev, E. P., Garfunkel, E., Gustafsson, T., & Urdahl, R. S. (1998). Intermixing at the tantalum oxide/silicon interface in gate dielectric structures. Applied Physics Letters, 73(11), 1517-1519. https://doi.org/10.1063/1.122191