Plasma and thermal ALD of Al2O3 in a commercial 200 mm ALD reactor

The deposition of Al2O3 by remote plasma atomic layer deposition (ALD) in the Oxford Instruments FlexAL reactor was studied and compared with results from thermal ALD in the same reactor. Trimethylaluminum [Al(CH3)(3)] was used as the metal precursor and O-2 plasma and H2O were used as oxidizing agents for the plasma and thermal processes, respectively. For remote plasma ALD with a total cycle time of 4 s, the growth per cycle decreased monotonically with substrate temperature, from 1.7 A/cycle at 25 degrees C to 1.0 angstrom/cycle at 300 degrees C. This growth per cycle was consistently higher than that obtained for thermal ALD. For the latter a maximum growth per cycle of similar to 1.0 angstrom/cycle was found at 200 degrees C. The film properties investigated were nearly independent of oxidant source for temperatures between 100 and 300 degrees C, with a slightly higher mass density for the remote plasma ALD Al2O3 films. Films deposited at 200 and 300 degrees C were stoichiometric with a mass density of 3.0 g/cm(3) and low C (< 1 atom %) and H (< 3 atom %) contents. At lower substrate temperatures, oxygen-rich films were obtained with a lower mass density and higher H-content. Remote plasma ALD produced uniform Al2O3 films with nonuniformities of less than +/- 2% over 200 mm diam substrates. Excellent conformality was obtained for films deposited in macropores with an aspect ratio of similar to 8 (2.0-2.5 mu m diam). Preliminary results on electrical properties of remote plasma deposited films showed high dielectric constants of 7.8 and 8.9 for as-deposited and forming gas annealed Al2O3, respectively. (C) 2007 The Electrochemical Society.