Epitaxial Growth of SrTiO 3 Thin Films on TiN/Si Substrates using RF Sputtering
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0966-T07-21
Epitaxial Growth of SrTiO3 Thin Films on TiN/Si Substrates using RF Sputtering Chun Wang and Mark H. Kryder Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213
ABSTRACT Epitaxial SrTiO3 (001) thin films with a TiN template layer have been deposited on Si(001) single crystal substrates by RF sputtering. The deposited SrTiO3 films show a surface with roughness of 0.66nm. The orientation relationship was determined to be SrTiO3(001)[110]||TiN(001)[110]||Si(001)[110]. The microstructure and interface of the multilayer were studied using high resolution transmission electron microscopy (TEM). The electron diffraction pattern confirmed the epitaxial relationship between each layer.
INTRODUCTION SrTiO3 is a very promising oxide material that has a high dielectric constant and that could be used in integrated devices like capacitors in dynamic random access memories (DRAMs), tunable devices and gate oxides for field effect transistors (FETs). Moreover, SrTiO3 could provide a good template for the integration of ferroelectric perovskite oxide films on Si substrates because it has a lattice constant similar to that of most ferroelectric perovskite oxides. Much research has been done to produce polycrystalline SrTiO3 films on Si substrates [1,2]. In the polycrystalline films, the grain boundaries could induce high leakage current paths and diffusion paths, which could cause the device to fail. To improve the device performance, high quality SrTiO3 single crystal films with smooth surfaces are needed. Molecular-beam epitaxy (MBE) and pulsed laser deposition (PLD) have been reported to produce high quality SrTiO3 films on Si substrates [3,4]. However, both PLD and MBE are difficult to use for manufacturing. RF sputtering is one of the most extensively used methods for the deposition of oxide films because it is relatively low cost and suitable for making large area films with good uniformity. Thus, it is important to study the epitaxial growth of SrTiO3 thin films on Si wafers using the RF sputtering method. In this paper, we describe the sputter-deposition of epitaxial SrTiO3 films on Si substrates with TiN as a template layer. The films have been characterized by X-ray diffraction, atomic force microscopy (AFM) and TEM.
EXPERIMENT The Si substrates were cleaned in acetone and isoproponal baths for 10 minutes in an ultrasonic container and then dipped in 10% HF solution for one minute to remove the surface native oxide on
Si before loading into a Leybold-Heraeus Z-400 sputtering system. The base pressure was about 6*10-7 Torr. Stoichiometric compound targets of TiN and SrTiO3 were used in the experiment. Deposition conditions such as temperature, power and working pressure were optimized to obtain samples with good crystallinity and smooth surfaces. The TiN template layer was then deposited at a substrate temperature of 450°C, followed by the SrTiO3 thin films sputter deposited at 540°C. The TiN films deposited above 500°C had poor crystal quality and rough surf
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