In situ ATR-FTIR analysis of surfactant adsorption onto silicon from buffered hydrofluoric acid solutions

A. Marcia Almanza-Workman, Srini Raghavan, Roger P. Sperline

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Buffered hydrofluoric acid (BHF) solutions containing HF and NH4F are widely used in the manufacturing of silicon-based integrated circuits. The adsorption/desorption characteristics of a commercially available, high purity, polyglycidol type surfactant (OHS) onto/from silicon from buffered hydrofluoric acid (BHF) solutions was studied by in situ attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). The challenge in these measurements was to resolve the C-H peaks, in the 2800-3000 cm-1 region of the surfactant spectrum, that were masked by the strong absorbance due to N-H caused by a large amount of NH4+ ions in the solution. A technique has been developed to overcome this limitation. The principle of this technique is to carry out the surfactant adsorption in BHF solutions followed by the replacement of NH4+ ions by alkali-metal cations, such as K+ and Cs+, to allow better resolution of the C-H peaks from the baseline. Extrapolation of the adsorption density to time zero yields the adsorption density in the presence of NH4+. Using this technique, the adsorption density of OHS surfactant in a buffered HF solution containing 7 parts of NH4F (40%) and 1 part of HF (49%) was found to be approximately 20% higher than that in dilute HF solutions.

Original languageEnglish (US)
Pages (from-to)3636-3640
Number of pages5
JournalLangmuir
Volume16
Issue number8
DOIs
StatePublished - Apr 18 2000

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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