Counting of electric charge for control of local metal plating using a scanning nanopipette probe microscope

We describe a deposition technique of nanometer-scale metal plating with controlling the deposition volume. The technique is based on a novel measurement technique of electric charge during the metal plating deposition using a scanning probe microscope with a nanopipette probe. The nanopipette with an aperture approximately 200 nm in diameter was filled with CuSO₄ electrolyte aqueous solution. A Cu metal plating dot was electrochemically deposited on the Au surface as the nanopipette probe was nearly in contact by applying a dc bias voltage between the electrolyte solution and the surface. The volume of the deposited Cu dot is dependent on the electric charge during the electrochemical reaction. Therefore, to control the deposited volume of metal plating, the ionic current was measured and counted as the electric charge. By counting amount of the electric charge, it was possible to control the deposited volume of the Cu dot. The advantage of the electric charge counting was evaluated by the deposition of dot arrays. The measurement technique of the electric charge to control the deposition volume is applicable for various fabrications of nanometer-scale structures in the fields such as nanomechanics and nanoelectronics.