Chemically conformal ALD of SrTiO3 thin films using conventional metallorganic precursors

SrTiO3 (STO) thin films were grown on Si wafer, Pt- and Ru-coated Si wafers, respectively, by an atomic layer deposition (ALD) technique using conventional metallorganic precursors, Sr(C11H19O2)(2)(Sr(thd)(2)) and Ti(Oi-C3H7)(4) (TTIP) as Sr- and Ti-precursors, respectively, with a remote-plasma activated H2O vapor as the oxidant at a wafer temperature of 250 degrees C. Patterned Si wafers with contact holes having a diameter of 0.13 and 1 mu m depth (aspect ratio of 8) was used in order to test the film-thickness and cation-composition conformalities over the contact hole surface. The ALD behavior of the STO film was critically dependent on the Sr(thd)(2) source heating temperature. When the Sr source temperature was < similar to 200 degrees C [Sr(thd)(2) melting temperature] stoichiometric STO films were deposited with a good process reliability. Excellent film thickness and cation composition conformalities (nonuniformity < 3%) over the severe contact hole structure were obtained by the optimized precursor supply and deposition conditions. It was also observed that most of the input TTIP precursor molecules did not chemically adsorb on the SrO surface, possibly due to oversaturation of the SrO surface by the Sr(thd)(2) molecules or thermally modified Sr(thd)(2) molecules as a result of the heating process of the Sr(thd)(2) when the Sr- source temperature was > 200 degrees C. This difficulty resulted in a nonuniform cation composition ratio along the contact hole. (c) 2005 The Electrochemical Society. All rights reserved.