Formation Process and Electrical Property of RuO2 Thin Films Prepared by Reactive Sputtering

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Ir and IrO2 thin films were prepared by reactive sputtering in Ar+O2 gas. The formation process of Ir and IrO2 films was classified into three regions depending on the O2 flow ratio; (a) metal region, (b) high deposition rate oxide region, and (c) low deposition rate oxide region. Supplied O2 molecules in region (a) were gettered by Ir atoms sputtered on the chamber wall and O2 partial pressure was very low. In region (b), since the amount of supplied O2 molecules exceeds the total amount of sputtered Ir atoms, IrO2 films are formed at the substrate surface. In region (c) the surface of the Ir target is thought to be oxidized and the deposition rate of IrO2 film decreases. Resistivity of the IrO2 films decreases with an increase of substrate temperature and the minimum resistivity of 83 µΩcm is obtained at 400°C. However, mixture-phase films of Ir and IrO2 were formed at 500°C.