Synthesis of ammonium silicon fluoride cryptocrystals on silicon by dry etching

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Abstract

Cryptocrystal layers of ammonium silicon fluoride (NH 4 ) 2 SiF 6 were synthesized on silicon wafers by dry etching method using vapor of the mixture of HF and HNO 3 solutions at room temperature. Crystalline layers having thicknesses of up to 8 μm have been produced at growth rates of around 1m/h. The crystallinity was analyzed by X-ray diffraction that indicates an isometric hexoctahedral system (4/m -32/m) with Fm3m space grouping of (NH 4 ) 2 SiF 6 cryptohalite crystals. These results have been confirmed by the presence of vibrational absorption bands of (NH 4 ) 2 SiF 6 species by Fourier transform infrared (FTIR) spectroscopic measurements. Strong absorption bands were observed in the infrared at 480, 725, 1433 and 3327cm -1 and assigned to N-H and Si-F related vibrational modes of (NH 4 ) 2 SiF 6 . Annealing above 150°C leads to the formation of individual crystals with sizes up to 20 μm on the surface, thus indicating the possibility of forming solid compound layers with fine grain sizes on silicon.

Original languageEnglish
Pages (from-to)336-341
Number of pages6
JournalApplied Surface Science
Volume236
Issue number1-4
DOIs
Publication statusPublished - 15 Sept 2004
Externally publishedYes

Keywords

  • Ammonium silicon fluoride
  • Cryptocrystal
  • Cryptohalite
  • Dry etching
  • Fluorosilicate
  • Low-k dielectrics
  • Porous silicon
  • Silicon
  • Surface treatment
  • Vibrational spectroscopy

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