Low-resistivity PVD α-tantalum: phase formation and integration in ultra-low k dielectric/copper damascene structures

This paper describes the formation and application of a PVD tantalum diffusion barrier in its low-resistivity α-phase in Cu/ultra low-k integration. The desirable low-resistivity tantalum phase forms readily when deposited directly on the low-k CVD dielectric at deposition temperatures below 100°C by non-reactive sputtering and without any base or seed layers. This has not been reported in literature before. The paper discusses the mechanism of α-Ta phase formation and other film properties, including the influence of the Ta barrier on the [111] texture in subsequently deposited PVD Cu seed layers.