Evaluation of Ta and TaN-based Cu diffusion barriers deposited by Advanced Hi-Fill (AHF) sputtering onto blanket wafers and high aspect ratio structures

This paper investigates the properties of Ta and Ta(N) barrier layers deposited by Advanced Hi-Fill(TM) (AHF) sputtering onto both blanket and patterned wafers. The differences, in terms of forming an effective diffusion barrier, between Ta and Ta(N) barriers of varying N, content and the important integration issues that are brought about by the comparison of blanket and patterned wafers are emphasised. In particular, from the blanket study we find that Ta(N) films with high N, content form the best diffusion barriers to Cu, while the study on patterned wafers indicates that an intermediate N, flow consistent with a blanket deposition of mixed phase b.c.c. and beta Ta forms the optimum barrier in terms of maximised sidewall coverage and material quality. (C) 2002 Elsevier Science B.V. All rights reserved.