Electroless Deposition of Copper by fjhuangjun


									     Electroless Deposition of Copper: Nano-scale
        topography from Micro-scale kinetics
                                                               This approach has allowed the synergistic effect of the
    D. Plana, R.A.W. Dryfe, S.D. Patole and G. Shul            half-reactions on one another to be quantified for a
               University of Manchester                        specific electroless system (deposition of Cu on Au, using
    School of Chemistry, Oxford Road, Manchester               dimethylamine borane, DMAB) as a reducing agent.
            M13 9PL, UNITED KINGDOM                            Linear growth rates are found with the electroless bath for
                                                               the Cu-DMAB system, with an apparent induction time of
The process of electroless deposition, although widely         the order of 30 s: the growth rate, growth law and the
used technologically, is poorly understood on a                induction time all change when deposition is performed in
mechanistic level. Open questions concerning the process       the bipolar cell of Figure 1, compared to the electroless
include: what is the extent of interaction between the         bath.
reduction (metal deposition) process and the oxidation          In addition to the kinetic data, we have also studied the
reaction of the reducing agent [1]? Electrochemical            evolution of the Cu deposit morphology, in particular the
techniques can probe the individual redox processes, but       effect on morphology of use of the separate (bipolar) cell,
the synergy between the two reactions that is believed to      compared to the electroless bath. In situ and ex situ
occur in actual electroless baths is lost. We have recently    atomic force microscopy (AFM) has been used as the
developed a method based on a bipolar cell as a probe of       probe here, an example micrograph is shown in Figure 2.
electroless bath chemistry [2]. The deposition rate
measured in the bipolar cell, which is illustrated in Figure
1, can be compared with the rate obtained in standard
electroless baths. Importantly, the potential difference of
the bipolar cell can be biased, to probe the sensitivity of
the overall electroless process to potential.
                                                                   1. H. Wiese, K.G. Weil, Ber. Bunsen. Phys. Chem.,
Figure 1: Bipolar cell configuration used to probe                     91 (1987) 619.
electroless deposition.                                            2. D. Plana, G. Shul, M.J. Stephenson and R.A.W.
                                                                       Dryfe, Electrochem. Comm., 11 (2009) 61.

Figure 2: AFM of Cu deposited from electroless bath on
Au foil, using DMAB as reducing agent.

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