Controlled and Localized Electrochemical Microfabrication with Moving Sub-Micron Rounded Tip as Tool Electrode

Electrochemical reaction has been extensively applied to fabricate microstructures. Electrochemical micromachining (EMM) with ultrashort voltage pulses holds great potential in micromachining with sub-micro or nano precision. In this paper, a moving sub-micro spherical tip was adopted to EMM in processing microchannels with the controlled profiles and sub-micro accuracy. Both the mechanisms and advantages of EMM using the moving spherical tip were analyzed. The electric field density distribution on the workpiece surface determined the machined profile of the microchannels, which has been verified by simulation and experimental methods. An experimental setup for electrochemical micromachining was developed with a workpiece moving resolution of nanometer scale. Experiments were conducted to investigate the influences of the applied voltage, initial inter-electrode gap, and spherical tip diameter on the machined depth and precision of EMM. Results showed that microchannels with smaller gap could be processed with the lower voltage, proper smaller inter-electrode gap, and smaller spherical tip diameter. Microchannels with the width 0.9 μm and side gap 0.12 μm were fabricated by using applied voltage 4 V, spherical tip diameter 0.8 μm, inter-electrode gap 1.0 μm. Microchannels with the controlled profile and precision could be fabricated by EMM potentially. Preliminary experiments also demonstrated the possibility of high-aspect-ratio processing by layer-by-layer EMM with moving spherical tip as the tool electrode.