Inhomogeneous nucleation and growth of palladium and alloyed cobalt during self-aligned capping of advanced copper interconnects
We investigate the nucleation and growth of two cobalt alloys (CoWB and Pd-CoWP) used to encapsulate copper interconnects. We demonstrate that very uniform deposits are obtained across 300 mm wafers, with accurate thickness control. However, large local thickness variations are observed, possibly compromising the continuity of thin deposits. The origin of this phenomenon is first investigated by electron back scatter diffraction. A clear correlation between areas of dense Pd nucleation and the (111) grains of the polycrystalline copper surface is demonstrated. Then, an epitaxial relationship between the cobalt alloys and the underlying copper substrate is evidenced by TEM characterization. Local nucleation density could thus be affected by the substrate orientation, accounting for thickness inhomogeneities after growth. © 2010 Elsevier B.V. All rights reserved.
Keywords: 300 mm wafers ; Atomic force microscopy ; Backscattering ; Cobalt ; Cobalt alloys ; Cobalt compounds ; Copper ; Copper interconnects ; Copper substrates ; Deposits ; Diffraction ; Electroless deposition ; Electron back scatter diffraction ; Electrons ; Epitaxial growth ; Epitaxial relationships ; Epitaxy ; Inhomogeneities ; Nucleation ; Nucleation and growth ; Nucleation densities ; Palladium ; Polycrystalline copper ; Self-aligned ; Substrate orientation ; TEM characterization ; Thickness variation ; Transmission electron ; Transmission electron microscopy
Record created on 2014-11-14, modified on 2016-08-09