Atomic Layer Deposition of Iridium Oxide Thin Films on Tungsten and Si Substrates

Abstract

Both Iridium and Iridium oxide thin films have been extensively investigated for their various applications. For Ir, it is a potential optical material in Fresnel zone, X-ray microchannel plates, inductive grid filters. On the other hand, iridium Oxide films can be used as a reference electrode and PH measurment in the field of biology environment and the food, nuclear, gas and oil industry due to their low resistivity, high transmittance, biocompatibility and good oxygen diffusion barrier properties [1,2]. The Atomic layer deposition (ALD) is considered as a half reaction of a chemical vapor depositon (CVD), where diferent ALD chemical precuresors are alternatively introduced into an ALD reaction chamber. The self-limiting surface reactions in each ALD cycle consequently result in precise layer thickness control, stoichiometry, composition, uniformity of large area on the substrate. ALD also can be used to deposit conformal film onto very complex substrate or template surfaces. In addition the ALD thin films can be deposited at low growth temperature. Therse are the advantageous properties of ALD which make it more competitive and promising. In this work, the irdium oxide films were grown on Si and tungsten substrates by ALD using (Ethylcyclopentadienyl) (1, 5-cyclooctadien) iridium (C14H19Ir) and H2O/O2 as precursors for iridium and oxygen, respectively. The C14H19Ir was heated to 50 oC, while the H2O and O2 precursors remained at room temperature. The ALD for growth temperature was varied over a range of various temperatures in order to determine the ALD process window. The iridium oxide thin films were subsequently annealed at 700 oC for 1 hour in a furnace under O2 atmosphere. In this study we report successful synthesis of IrO2 films on tungsten metal substrates and native oxide covered Si wafers. Detailed physical characterization of ALD Iridium oxide thin films has been performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), UV-VIS-NIR spectrometer.