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Diffusion barriers

: Hecker, M.; Hübner, R.


Baklanov, M.R.; Ho, P.S.; Zschech, E.:
Advanced interconnects for ULSI technology
Chichester: Wiley, 2012
ISBN: 978-0-470-66254-0 (Print)
DOI: 10.1002/9781119963677
Aufsatz in Buch
Fraunhofer IZFP, Institutsteil Dresden ( IKTS-MD) ()

The utilization of copper as an interconnect material requires application of barrier films in order to prevent outdiffusion of copper into surrounding materials and to obtain desired electrical and mechanical parameters of the interconnects. In this chapter, the properties of different types of barrier films suited for present and future CMOS technology nodes are discussed. Apart from their material, interface and microstructural properties, deposition and characterization techniques are also discussed in detail. After reviewing properties of widely used refractory-metal barriers, such as those based on Ta, W and Ti, including various stacks and composites of these and other metal-consisting barriers, the focus is on advanced barrier systems. Examples are Ru-based films enabling direct Cu plating and systems possessing improved reliability properties as obtained for interconnects with CoWP-based cap films or self-forming barriers on the basis of Cu(Mn) alloys. Approach es to obtain conformal diffusion barriers with thicknesses significantly below 5 nm, such as self-assembled molecular nanolayers and polymer-based barriers, are also discussed. A key for successful development of future barrier systems will be a detailed understanding of their properties and defect mechanisms on the nanoscale.