Competition between Al2O3atomic layer etching and AlF3atomic layer deposition using sequential exposures of trimethylaluminum and hydrogen fluoride.
The thermal atomic layer etching (ALE) of Al2O3can be performed using sequential and self-limiting reactions with trimethylaluminum (TMA) and hydrogen fluoride (HF) as the reactants. The atomic layer deposition (ALD) of AlF3can also be accomplished using the same reactants. This paper examined the competition between Al2O3ALE and AlF3ALD using in situ Fourier transform infrared (FTIR) vibrational spectroscopy measurements on Al2O3ALD-coated SiO2nanoparticles. The FTIR spectra could observe an absorbance loss of the Al-O stretching vibrations during Al2O3ALE or an absorbance gain of the Al-F stretching vibrations during AlF3ALD. The transition from AlF3ALD to Al2O3ALE occurred versus reaction temperature and was also influenced by the N2or He background gas pressure. Higher temperatures and lower background gas pressures led to Al2O3ALE. Lower temperatures and higher background gas pressures led to AlF3ALD. The FTIR measurements also monitored AlCH3* and HF*species on the surface after the TMA and HF reactant exposures. The loss of AlCH3* and HF*species at higher temperatures is believed to play a vital role in the transition between AlF3ALD at lower temperatures and Al2O3ALE at higher temperatures. The change between AlF3ALD and Al2O3ALE was defined by the transition temperature. Higher transition temperatures were observed using larger N2or He background gas pressures. This correlation was associated with variations in the N2or He gas thermal conductivity versus pressure. The fluorination reaction during Al2O3ALE is very exothermic and leads to temperature rises in the SiO2nanoparticles. These temperature transients influence the Al2O3etching. The higher N2and He gas thermal conductivities are able to cool the SiO2nanoparticles more efficiently and minimize the size of the temperature rises. The competition between Al2O3ALE and AlF3ALD using TMA and HF illustrates the interplay between etching and growth and the importance of substrate temperature. Background gas pressure also plays a key role in determining the transition temperature for nanoparticle substrates.
Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA.
Jaime W
JW
DuMont
Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA.
Steven M
0000000302539184
SM
George