AVS 52nd International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuM

Paper TF-TuM3
Atomic Layer Deposition of SrTiO@sub 3@ Films Having a High Thickness- and Cation-Composition Conformality Over a Severe Contact Hole Structure

Tuesday, November 1, 2005, 9:00 am, Room 306

Session: Atomic Layer Deposition - Oxides
Presenter: O.S. Kwon, Seoul National University, Korea
Authors: O.S. Kwon, Seoul National University, Korea
S.W. Lee, Seoul National University, Korea
C.S. Hwang, Seoul National University, Korea
Correspondent: Click to Email
SrTiO@sub 3@ (STO) thin films were grown on Si wafer and Ru-coated Si wafers, respectively, by an atomic-layer-deposition (ALD) technique using conventional metal organic precursors, Sr(C@sub 11@H@sub 19@O@sub 2@)@sub 2@ (Sr(thd)@sub 2@) and Ti(Oi-C@sub 3@H@sub 7@)@sub 4@ (TTIP) as Sr- and Ti-precursors, respectively, with a remote-plasma activated and thermal H@sub 2@O vapor as oxidant. Although the each precursor exhibited ALD reaction with the remote-plasma activated H@sub 2@O vapor, STO exhibited quite different deposition behavior with the bubbling temperature of Sr(thd) @sub 2@. The cation stoichiometry of STO films was dramatically improved when the bubbling temperature of Sr(thd) @sub 2@ < 200°C (melting temperature of Sr(thd) @sub 2@) irrespective of the type of oxidants. Furthermore, cation composition conformality over the severe contact hole structure (0.13µm opening diameter with an aspect ratio of 8) was highly improved when the Sr(thd)@sub 2@ bubbling temperature was 180°C. The thickness step coverage over the entire contact hole was >95%, and the variation of cation composition was very small (< 3%). The different degree of oligomerization of Sr(thd)@sub 2@ with the bubbling temperature was supposed to be the reason for these phenomena. Electrical properties of STO films grown by ALD were highly dependent on the amount of oxidant. Leakage current density of STO films with lower oxidant supply was too high to measure the dielectric properties. The high leakage property was directly related to the binding energy shift into high binding energy direction of Sr 3d peak position in the XPS analysis. The leakage current density of STO films with sufficient oxidant was reduced and the binding energy shift of Sr 3d peak was reduced. Equivalent oxide thickness < 1nm and leakage current density < 10@super -6@A/cm@super 2@ at 1V were obtained by the optimized two step deposition and post-annealing processes.