Plasma and Thermal ALD of Al[sub 2]O[sub 3] in a Commercial 200 mm ALD Reactor

Abstract

The deposition of Al 2 O 3 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 AlCH 3 3 was used as the metal precursor and O 2 plasma and H 2 O 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 /cycle at 25C to 1.0 /cycle at 300C. This growth per cycle was consistently higher than that obtained for thermal ALD. For the latter a maximum growth per cycle of 1.0 /cycle was found at 200C. The film properties investigated were nearly independent of oxidant source for temperatures between 100 and 300C, with a slightly higher mass density for the remote plasma ALD Al 2 O 3 films. Films deposited at 200 and 300C 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 Al 2 O 3 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 8 2.0-2.5 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 Al 2 O 3 , respectively.