Microstructural characterization of sputter-deposited Pt thin film electrode
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Dong-Yeon Park and Dong-Su Lee Inostek Incorporated, 356-1 Gasan-dong, Keumchun-gu, Seoul 153-023, Korea (Received 21 May 2003; accepted 7 October 2003)
Pt thin films of various thicknesses (30 nm ∼ 200 nm) were deposited on Si wafers with SiO2, Ti, TiO2, or IrO2 buffer layers at various temperatures (room temperature ∼200 °C) by a direct current magnetron sputtering process. The Pt films showed a strong (111)-preferred texture irrespective of the thickness, under-layer, and growth temperature. The authors previously reported [J-E. Lim, D-Y. Park, J.K. Jeong, G. Darlinski, H.J. Kim, and C.S. Hwang, Appl. Phys. Lett. 81, 3224 (2002)] that the films were composed of three kinds of grains with slightly different (111) lattice parameters (bulklike, 1.0% and 2.1% larger). This study details the microstructural variations of the Pt films according to the variations of experimental parameters. The different deposition conditions produced slightly different crystalline structures, but the three different (111) lattice parameters were always found. Epitaxial (200) Pt films on a (200) MgO substrate and a highly (111) textured Au thin film on a SiO2/Si did not show the same splitting in the lattice parameter. The grains with 1.0% and 2.1% larger (111) lattice parameter almost disappeared after postannealing at 1000 °C. However, surface chemical binding of the Pt film before and after annealing was unchanged. Therefore, it is believed that the lattice parameter splitting in the (111) textured Pt film originated from the interfacial grains with the distorted crystal structure due probably to growth stress.
I. INTRODUCTION
Noble metal thin films such as Pt, Ir, and Ru, especially Pt thin films, have been extensively used as the electrodes of the ferroelectric and high-dielectric functional devices due mainly to their chemical inertness. The crystallization behavior and, thus, the electrical properties of these functional thin films are critically dependent on the structure of the underlying Pt electrode. Therefore, understanding and control of the Pt electrode are critically important to obtain the desired performances of the devices. There have been numerous reports on the growth and characterization of Pt films on various substrates using various methods. The reported growth methods include on- and off-axis magnetron sputtering,1–3 electron beam evaporation,4,5 metal–organic chemical vapor deposition6,7 and electroplating.8 Among them, magnetron sputtering might be the most suitable method for most a)
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J. Mater. Res., Vol. 19, No. 2, Feb 2004 Downloaded: 11 Mar 2015
applications (excluding applications requiring conformality of the electrode such as dynamic random access memory capacitors) for its good quality control, large area deposition, and mature deposition tool technologies. The sputtered-Pt thin films usually show a highly (111) textured growth behavior (the 〈111〉 direction of the film is parallel to the
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