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Title: Waterless TiO{sub 2} atomic layer deposition using titanium tetrachloride and titanium tetraisopropoxide

The surface chemistry for TiO{sub 2} atomic layer deposition (ALD) typically utilizes water or other oxidants that can oxidize underlying substrates such as magnetic disks or semiconductors. To avoid this oxidation, waterless or oxidant-free surface chemistry can be used that involves titanium halides and titanium alkoxides. In this study, waterless TiO{sub 2} ALD was accomplished using titanium tetrachloride (TiCl{sub 4}) and titanium tetraisopropoxide (TTIP). In situ transmission Fourier transform infrared (FTIR) studies were employed to study the surface species and the reactions during waterless TiO{sub 2} ALD. At low temperatures between 125 and 225  °C, the FTIR absorbance spectra revealed that the isopropoxide species remained on the surface after TTIP exposures. The TiCl{sub 4} exposures then removed the isopropoxide species and deposited additional titanium species. At high temperatures between 250 and 300  °C, the isopropoxide species were converted to hydroxyl species by β-hydride elimination. The observation of propene gaseous reaction product by quadrupole mass spectrometry (QMS) confirmed the β-hydride elimination reaction pathway. The TiCl{sub 4} exposures then easily reacted with the hydroxyl species. QMS studies also observed the 2-chloropropane and HCl gaseous reaction products and monitored the self-limiting nature of the TTIP reaction. Additional studies examined the waterless TiO{sub 2} ALD growthmore » at low and high temperature. Quartz crystal microbalance measurements observed growth rates of ∼3 ng/cm{sup 2} at a low temperature of 150  °C. Much higher growth rates of ∼15 ng/cm{sup 2} were measured at a higher temperature of 250  °C under similar reaction conditions. X-ray reflectivity analysis measured a growth rate of 0.55 ± 0.05 Å/cycle at 250  °C. X-ray photoelectron depth-profile studies showed that the TiO{sub 2} films contained low Cl concentrations <1 at. %. This waterless TiO{sub 2} ALD process using TiCl{sub 4} and TTIP should be valuable to prevent substrate oxidation during TiO{sub 2} ALD on oxygen-sensitive substrates.« less
Authors:
; ;  [1] ;  [2] ;  [3]
  1. Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215 (United States)
  2. Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309-0424 (United States)
  3. Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215 and Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309-0427. (United States)
Publication Date:
OSTI Identifier:
22258680
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 32; Journal Issue: 1; Other Information: (c) 2014 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DEPOSITION; FOURIER TRANSFORMATION; HYDRIDES; HYDROCHLORIC ACID; HYDROXIDES; INFRARED SPECTRA; MAGNETIC DISKS; MASS SPECTROSCOPY; MICROBALANCES; OXIDATION; PROPYLENE; QUARTZ; SEMICONDUCTOR MATERIALS; SUBSTRATES; SURFACES; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0400-1000 K; TITANIUM CHLORIDES; TITANIUM OXIDES; X RADIATION