On the action of magnetic gradient forces in micro-structured copper deposition

G. Mutschke¹ - K. Tschulik² - T. Weier³ - M. Uhlemann² - A. Bund⁴ - A. Alemany⁵ - J. Fröhlich¹

¹ Institute of Fluid Mechanics, Technische Universität Dresden, 01062 Dresden, Germany
² IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany
³ MHD Department, Helmholtz Zentrum Dresden-Rossendorf, 01314 Dresden, Germany
⁴ Institute Electrochemical Electroplating, Technische Universität Ilmenau, 98693 Ilmenau, Germany
⁵ SIMAP/Domaine Universitaire, BP 75 O 38402 Saint Martin d'Hères, France

Abstract
The relative influence of the Lorentz force and magnetic gradient force on micro-structured copper deposition is studied with simple magnetic elements consisting of cylindrical permanent magnets placed closely behind the surface of the cathode. Analytical findings and numerical simulations reveal that for magnets of small diameter the magnetic gradient force dominates. In experiments, it is found that the thickness of the deposited copper layer increases in the vicinity of the magnets. The combined analysis of simulations and experiments shows that this enhancement of mass transfer results from a local convection towards the electrode, which is forced by the magnetic gradient force. Finally, a more general case with electrically inert paramagnetic ions is discussed, where an inverse structuring effect can be expected. Figs 3, Refs 16.