Influence of deposition conditions on Ir/IrO2 oxygen barrier effectiveness

Abstract

The influence of the deposition temperature during the reactive sputtering process on the microstructure of thin Ir and IrO2 films deposited on oxidized Si substrates was investigated and related to the oxygen barrier effectiveness. For this purpose differential thermal analysis combined with residual gas analysis by mass spectrometry was used for the investigation of the microstructural and chemical behavior of the as-sputtered IrO2 films upon heating. Moreover, in situ stress relaxation analyses up to 900 °C, in and ex situ x-ray diffraction measurements were done for various annealing conditions. The investigated polycrystalline IrO2 films exhibited a large compressive stress and a distorted lattice due to the sputter deposition process. It is demonstrated that a high deposition temperature involves a delayed relaxation of the IrO2 grains which is causing an extrinsic, enhanced defect controlled oxygen mobility for the annealing temperatures below the recrystallization. The well-known low intrinsic oxygen diffusivity was only found in those samples which show—in addition to the recovery process—a recrystallization at low temperatures and thus a formation and growth of a new generation of grains with a lattice spacing as in bulk IrO2. Moreover, the oxygen diffusion in Ir films was investigated and the oxygen was found to penetrate the Ir films very quickly at elevated temperatures. The microstructure of the films was investigated by cross sectional transmission electron microscopy and it is shown that the cold-sputtered columnar IrO2 films protect the underlying layers from oxidation during a 700 °C high temperature oxygen anneal with an optimized Ir/IrO2 oxygen barrier stack.

Growth and characterization of vertically aligned self-assembled IrO2 nanotubes on oxide substrates

“…Conductive IrO 2 exhibits high thermal and chemical stability, making their films valuable as durable electrodes for oxygen evolution [10,11] and memory devices [12][13][14][15]. In recent reports, IrO 2 have also been studied as high performance and robust field emitters owing to its low work function, low resistivity and excellent stability against oxygen [16][17][18].…”

Amorphous and crystalline IrO2 thin films as potential stimulation electrode coatings

“…this material injects charge using a reversible charge injection reaction which is governed by a valence-change within the layer of the material. Iridium oxide thin films have also found considerable research interest for applications such as oxygen diffusion barrier materials in random access memory devices [12,13]. Iridium oxide (IrO 2 ) layers can be formed by anodic electrochemical activation of iridium metal (AIROF) [10,11,14,15], electrodeposition (EIROF) [16,17] onto a bulk material, thermal decomposition of an iridium salt (TIROF) [18], and by reactive sputtering using an iridium target (SIROF) [1,19,20].…”

A novel IrO2 electrode with iridium–titanium oxide interlayers from a mixture of TiN nanoparticle and H2IrCl6 solution

“…On contrary, the service life of Ti/IrO x -TiO 2 /IrO 2 electrode was much longer than Ti/IrO 2 electrode. On the one hand, the oxidation of TiN caused interlayer considerably expand [36], so that the surface cracks became relatively narrow and shallow. On the other hand, the formation of IrO x -TiO 2 solid solution and coherent interface among the thin titanium oxide layer, IrO x -TiO 2 interlayer and IrO 2 layer prevented oxygen migration.…”