Sono-electrodeposition transfer of micro-scale copper patterns on to A7 substrates using a mask-less method

A patterned anode tool was used to transfer electrodeposited microstructures on to an un-patterned A7 sized cathode by maintaining very narrow separation (300 µm) between the two electrodes and agitating the fluid in the inter-electrode gap by ultrasonic means. A non-acidic copper solution with a low content of metal ions and additives was used. Limiting current experiments were initially performed to demonstrate that improved and uniform agitation could be maintained within the inter-electrode gap at relatively low ultrasonic powers of 5 to 30 W L-1. The best pattern definition was obtained at a US power of 5 W L-1 and a current density of 20 mA cm-2. Importantly, the results obtained were comparable to those obtained by conventional through-mask plating. A single anode tool could be used to pattern up to five substrates, substantially minimising the amount of lithographic processing required. These results suggest that the proposed technique is a useful mask-less microfabrication process for pattern transfer on to large substrates.