Formation of low resistivity alpha Ta by ion beam sputtering

The properties of tantalum thin film prepared by ion beam sputtering with Xe ions (0.6–1.5 KV) have been investigated. β-Ta thin films with high resistivity (170 μΩ cm) on Si substrate were obtained without Cr underlayer. With Cr underlayer, however, a body-centered-cubic phase (bcc) α-Ta thin film with low resistivity (20 μΩ cm) has been successfully obtained at room temperature. The experimental results indicate that the Cr underlayer plays an important role in α-Ta formation and that the critical thickness of Cr is 20 Å. Properties of α-Ta are also influenced by Ta thickness and ion beam deposition process conditions. α-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.