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

Abstract

The EnFACE technology has been demonstrated as a successful mask-less electrodeposition method to transfer millimetre and micrometre-scale copper patterns on to A7-sized rectangular plates. This is the first successful demonstration of this technique using large substrates. A patterned anode tool was used to transfer electrodepositedpatterns onto anun-patterned 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-1and a current density of 20 mA cm-2. Importantly, the resultsobtained 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 processingrequired. These results suggest that the EnFACE techniqueis a usefulmask-less microfabrication process for pattern transfer on to large substrates.