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

Paper DI+EL-ThA4
Heterostructured Cu-Based Electrode for High-Dielectric Constant Oxide Thin Film Devices

Thursday, November 7, 2002, 3:00 pm, Room C-107

Session: Processing and Properties of Dielectric Materials
Presenter: W. Fan, Northwestern University
Authors: W. Fan, Northwestern University
O. Auciello, Argonne National Laboratory
S. Saha, Argonne National Laboratory
J.A. Carlisle, Argonne National Laboratory
D.M. Gruen, Argonne National Laboratory
R.P.H. Chang, Northwestern University
R. Ramesh, University of Maryland
Correspondent: Click to Email
Copper (Cu) has recently been introduced as an interconnect material in integrated sub-micron circuit technology, due to its low resistivity and high electro- and stress-migration resistance. The main problems inhibiting its application as an electrode material in high-dielectric constant (k) thin film capacitors are the Cu oxidation and diffusion during the growth of the high-k layer at relatively high temperature in an oxygen environment. To overcome these problems, heterostructured Ti-Al/Cu/Ta multilayers were fabricated on SiO2/Si substrates using ion beam sputtering deposition. The Ta layer acts a diffusion barrier to prevent high temperature-induced diffusion of Cu into the Si substrate, while the amorphous Ti-Al alloy layer provides the protection against oxidation of the Cu film during growth of the high-k materials. The diffusion and oxidation resistance of the Cu-based heterostructured electrode layer was investigated using a variety of complementary characterization techniques, including x-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), and four-point probe sheet resistance measurements. Analytical results showed that the Cu/Ta heterostructure remained intact through the annealing in 6 mTorr oxygen up to 600 °C. A thin oxide layer, formed on the Ti-Al surface, effectively prevented the oxygen penetration toward underneath layers. To test the feasibility of the proposed heterostructured electrode integrated with high-k thin films, complex oxide (Ba@sub x@Sr@sub 1-x@)TiO@sub 3@ (BST) layers were then deposited on Ti-Al/Cu/Ta by magnetron sputtering. Polycrystalline BST film was obtained at 500 °C and 600 °C, and the measured permittivity and leakage current density were 170 ~ 330 (at zero bias) and 10@super -6@ ~ 10@super -9@ A/cm@super 2@ (at 100 kV/cm) respectively.