Cu films were deposited on Si (10 0) substrates at room temperature by a non-mass separated ion beam deposition method. The effect of the negative substrate bias voltage on the property of the Cu films was investigated by using field emission scanning electron microscopy and secondary ion mass spectroscopy. The Cu film deposited at the negative bias voltage of -50 V showed an extremely fine and homogeneous morphology without a columnar structure. The purity of the Cu film deposited at the bias voltage of -50 V was much improved in comparison with the 6N Cu target, while the Cu film deposited without applying substrate bias voltage contained more impurities than the 6N Cu target. (C) 2003 Elsevier Science B.V. All rights reserved.