Rate-limiting reactions of growth and decomposition kinetics of very thin oxides on Si(001) surfaces studied by reflection high-energy electron diffraction combined with auger electron spectroscopy

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Abstract

The growth and decomposition kinetics of very thin oxides on Si(001) surfaces were investigated by reflection high-energy electron diffraction combined with Auger electron spectroscopy (RHEED-AES) to monitor the reaction rates of oxide growth and decomposition in real time, and changes in surface structure and interface morphology simultaneously. The oxides prepared by stopping the second oxide layer growth at various coverages following the first oxide layer growth by Langmuir-type adsorption at 500°C under an O 2 pressure of 2.6 × 10-4 Pa were isothermally annealed by increasing temperature from 500 to 666°C at the same time that O2 gas was quickly evacuated. It was observed that (1) oxide thickness continued to decrease significantly as measured on the basis of changes in O KLL Auger electron intensity ΔIO-KLL before voids appeared at a nucleation time tN as recognized by the appearance of half-order spots in RHEED patterns, (2) the SiO2/Si interface morphology was considerably roughened corresponding to ΔIO-KLL during void nucleation as observed by the evolution of the RHEED intensity of bulk diffraction spots ΔIbulk, (3) the ratio of ΔI bulk to ΔIO-KLL was almost constant, and (4) oxide decomposition rate during void nucleation, which was approximately given by ΔIO-KLL/tN, showed a good linear correlation with the second oxide layer growth rate α immediately before starting the decomposition reaction. The good correlation between ΔI O-KLL/tN and α clearly indicates that the rate-limiting reaction of the second oxide layer growth is closely related to that of the oxide decomposition during void nucleation. All the above-mentioned observations can be comprehensively interpreted using a reaction model proposed for the rate-limiting reactions of oxide growth and decomposition, in which the point defect generation (emitted Si atoms + vacancies) caused by the strain due to the volume expansion of oxidation plays a crucial role because of the high reactivity of the emitted Si atoms and vacancies with dangling bonds. Under an O2 atmosphere, both emitted Si atoms and vacancies are the preferential adsorption sites of O2 molecules in the oxide and at the SiO2/Si interface, respectively. The oxide can be decomposed by the emitted Si atoms to produce SiO molecules, which desorb from the surface, leading to oxide removal in vacuum with SiO2/Si interface morphology roughening, but may be oxidized within the oxide under an O2 atmosphere.

Original languageEnglish
Pages (from-to)7063-7079
Number of pages17
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume45
Issue number9 A
DOIs
Publication statusPublished - 2006 Sep 7

Keywords

  • AES
  • Decomposition
  • Emitted Si atom
  • Layer-by-layer oxidation
  • Oxidation
  • Point defect generation
  • RHEED
  • Rate-limiting reaction
  • Real-time monitoring
  • Silicon
  • Strain
  • Vacancy

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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