A new approach to control a deflection of an electroplated microstructure: dual current electroplating methods

Abstract

We propose and demonstrate a simple and novel method to control the deflection in a suspended microstructure by using a dual current electroplating (DuCE) method. The key concept of this method is to divide the structure into two layers-a bottom layer and a top layer-and then apply respective current densities in electroplating to those two layers while all other conditions are kept the same. In addition to a flat structure, the direction of structure bending is freely controlled by virtue of the DuCE method. Cantilever Ni beams with a length of 400 mu m, which were electroplated by the conventional single current electroplating method, bent downward with a deflection of 3.4 mu m. On the contrary, by the DuCE method, cantilever beams with a length of 400 mu m showed an almost flat structure as desired. (The current densities of the bottom layer, the top layer, and the ratio of the two current densities, are 0.15, 1.24 A dm(-2), and 8.3, respectively.) Consequently, a nickel electroplated spiral structure with a length of 8600 mu m was suspended flat with an end deflection of less than 0.7 mu m (the ratio between the deflection and length is 0.007%). This work therefore represents the unprecedented ultra-long suspended microstructure with submicrometer deflection.