The properties of tantalum thin film prepared by ion beam sputtering with Xe ions (0.6-1.5 KV) have been investigated. beta-Ta thin films with high resistivity (170 muOmega cm) on Si substrate were obtained without Cr underlayer. With Cr underlayer, however, a body-centered-cubic phase (bcc) alpha-Ta thin film with low resistivity (20 muOmega cm) has been successfully obtained at room temperature. The experimental results indicate that the Cr underlayer plays an important role in alpha-Ta formation and that the critical thickness of Cr is 20 Angstrom. Properties of alpha-Ta are also influenced by Ta thickness and ion beam deposition process conditions. alpha-Ta with lower resistivity was achieved by using approximate beam energy of 1000 eV and beam current of 150 mA. X-ray diffraction analysis indicates that changes in resistivity can be attributed to changes in microstructure that is influenced by the ion beam conditions. (C) 2003 American Vacuum Society.