Surface chemistry of plasma-assisted atomic layer deposition of Al2O3 studied by infrared spectroscopy

The surface groups created during plasma-assisted atomic layer deposition (ALD) of Al2O3 were studied by infrared spectroscopy. For temperatures in the range of 25–150°C, –CH3 and –OH were unveiled as dominant surface groups after the Al(CH3)3 precursor and O2 plasma half-cycles, respectively. At lower temperatures more –OH and C-related impurities were found to be incorporated in the Al2O3 film, but the impurity level could be reduced by prolonging the plasma exposure. The results demonstrate that –OH surface groups rule the surface chemistry of the Al2O3 process and likely that of plasma-assisted ALD of metal oxides from organometallic precursors in general.