Low resistivity α-tantalum in Cu/CVD low-k (Orion™) integration

Over the past years, most research on Ta-based diffusion barriers in Cu metallisation has been focused on high resistivity beta-Ta (p = 160-200 muOmega cm) as well as on binary and ternary tantalum-alloys with relatively little work published on the properties of low-resistivity alpha-Ta (p = 15-30 muOmega cm) in Cu/low-k integration. The present paper describes the deposition of alpha-Ta directly onto a CVD low-k dielectric with k < 2.2 (Orion(TM)) by non-reactive sputtering at deposition temperatures below 1000 degreesC. In addition to pure alpha-Ta films, the PVD system employed in the present study allows the controlled formation of mixed phases and hence 'tuning' of barrier properties such as resistivity or barrier strength. Film characterisation includes resistivity, in-plane stress, texture and the ability to promote a {111} texture in the subsequently PVD Cu seed layer. (C) 2002 Elsevier Science B.V. All rights reserved.