The effect of the oxygen exposure on ruthenium atomic layer deposition (ALD) was investigated. Ru ALD was carried out using bis (cyclopentadienyl)ruthenium and oxygen gas. To investigate the effect of the oxygen exposure, the total oxygen exposure was changed by two different ways; change of exposure time at a constant flow and change of flow at a constant exposure time. While the increase in oxygen exposure time did not change the film properties, the increase in the oxygen flow rate resulted in a significant increase in the growth rate and resistivity. The properties of ALD Ru films prepared at different oxygen exposure conditions were analyzed by various techniques including synchrotron radiation X-ray diffraction, X-ray photoelectron spectroscopy, X-ray reflectivity, and transmission electron microscopy. The growth mechanism is discussed based on the analysis results. (c) 2008 Elsevier B.V. All rights reserved.