AVS 49th International Symposium
    Dielectrics Thursday Sessions
       Session DI+EL-ThA

Paper DI+EL-ThA5
Investigation of the Interfacial Region of (Ba,Sr)TiO@sub 3@ Thin Films Deposited on Pt Substrates by MOCVD

Thursday, November 7, 2002, 3:20 pm, Room C-107

Session: Processing and Properties of Dielectric Materials
Presenter: T.C. Kaspar, University of Washington
Authors: T.C. Kaspar, University of Washington
L.V. Saraf, Pacific Northwest National Laboratory
C.L. Aardahl, Pacific Northwest National Laboratory
J.W. Rogers, Jr., Pacific Northwest National Laboratory
T.S. Dory, Intel Corporation
Correspondent: Click to Email
Thin films of (Ba,Sr)TiO@sub 3@ (BST) have been extensively investigated as high-permittivity materials for microelectronics applications such as dynamic random access memory (DRAM) and advanced packaging components. By controlling the bottom electrode composition, electrode/film interface, and film stoichiometry and structure, the dielectric properties of the film can be tailored. In this study, BST thin films are deposited by MOCVD at low temperatures (500-575°C) using liquid delivery of metalorganic @beta@-diketonate precursors on Pt/Ti/Si(100), Pt/Cr/Si(100), and MgO(100) substrates. A (Ba,Sr)TiO@sub 3@ film deposited on Pt/Ti/Si with a bulk composition of (Ba+Sr)/Ti = 57 / 43 forms a thick titanium-rich interfacial region at the platinum interface, with a composition of (Ba+Sr)/Ti = 36 / 64, which adversely affects the dielectric properties of the film (@epsilon@@sub r@ = 84). Since titanium enrichment is not observed in deposition on MgO substrates, the unique precursor chemistry that occurs on the platinum surface plays a role in the formation of the interfacial region. To better understand the effect of titanium non-stoichiometry on the dielectric properties, a BST film was deposited with a titanium-rich composition of (Ba+Sr)/Ti = 35 / 65. After annealing at 750°C, the film exhibited a low dielectric permittivity of @epsilon@@sub r@ = 92 and a leakage current density of J@sub L@ = 8.7x10@super -5@ A/cm@super 2@. The mechanisms of excess titanium incorporation in the interfacial region, its effect on the dielectric properties, and its reduction or elimination are discussed.