Similarity approach for the measurement of local current density on micropatterned electrodes

Miniaturized motors or circuits are usually manufactured by the electrodepo sition of copper on micropatterned substrates, with feature dimensions of t he order of 50 mu m. Local growth rate over such electrodes can be predicte d by numerical codes of increasing capacity and accuracy, but very few expe rimental data are available for validation of these codes, due to the techn ical difficulty in measuring local current density over the microfeatures. The paper deals with the development and the use of a similarity approach f or the design of an enlarged scale model to enable local variables to be me asured at the active area of the features. The dimensions of the scale mode l have to allow microelectrodes or other microsensors to be inserted in the active horizontal and vertical walls of the features, and the operating co nditions have to be representative to those in the actual, microscale syste m, with respect to mass, momentum, and charge transfers. The case of lamina r flow over patterned electrodes with inactive area at the bottom of the ca vity between two neighboring tracks, has been considered. The feasibility o f the scaling-up technique for the design of a model with feature height at 1 or 10 mm is discussed. (C) 2000 The Electrochemical Society. S0013-4651( 99)11-093-0. All rights reserved.