AVS 49th International Symposium
    Dielectrics Wednesday Sessions
       Session DI+EL-WeP

Paper DI+EL-WeP7
Improvement of (Ba,Sr)TiO@sub 3@ Dielectric Properties by in-situ Formation of IrO@sub 2@ on Ir Electrodes

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Poster Session
Presenter: C.H. Lai, National Tsing Hua University, Taiwan
Authors: C.H. Lai, National Tsing Hua University, Taiwan
Y.C. Wu, National Tsing Hua University, Taiwan
W.C. Chen, National Tsing Hua University, Taiwan
S. Ma, Applied Materials
Correspondent: Click to Email
The (Ba,Sr)TiO@sub 3@ (BST) thin films grown on Ir bottom electrodes have showed high dielectric constants and low leakage current density, which are generally attributed to the formation of IrO@sub 2@ at the BST/Ir interface. The IrO@sub 2@ can decrease the accumulation of the oxygen vacancies, and typically was formed during the post-annealing process. In this work, we use high working pressure (47 mtorr) during rf sputtering deposition to enhance the in-situ formation of IrO@sub 2@ without post-annealing. We verified that oxygen plasma bombardment on the Ir surface during the deposition of BST films was the dominant mechanism for IrO@sub 2@ formation under the condition of high working pressure. The as-deposited BST films of 100 nm grown at 500 C show a dielectric constant as large as 550 (at 10 kHz); however, the leakage current is relatively large (10@super -4@ A/cm@super 2@ at 200 kV/cm). The large leakage current resulted from rough interface due to formation of thick IrO@sub 2@. To reduce leakage current, the double-layer technology was used, in which a thin BST film (5 nm) was deposited with pure Ar, and followed by deposition of a thick film (95 nm) with mixture gas (Ar/O@sub 2@). The thin BST layer can significantly reduce the roughness of IrO@sub 2@, resulting in lower leakage current (10@super -6@ A/cm@super 2@); however, since this thin BST layer is oxygen-deficient, the dielectric constant is slightly reduced. When the total BST thickness decreased, the reduction of dielectric constant becomes significant in the double-layer structure. For 30 nm BST films, we applied a dc substrate bias (-100V) during BST deposition to manipulate the film structure. The substrate bias significantly increases the film density and grain size, and at the same time reduces the roughness. Consequently, a large dielectric constant (220 at 10KHz) and a quite low leakage current (10@super -9@ A/cm@super 2@) were obtained in 30 nm BST films.