Laser-Assisted Liquid-Phase Etching of Copper Conductors and its Application to Advanced Integrated Circuit Interconnect

ABSTRACTWe have demonstrated a method f or the selective-area, laser-assisted liquid-phase etching of 6-μm thick copper conductors, by focusing the 488-μm line of an argon ion laser onto the surface of samples immersed in a dilute solution containing sulfuric acid and hydrogen peroxide. Average etch rates of up to 5.0 μm/s have been achieved, in the process of completely severing 14-μm wide copper lines, with little attendant damage to the underlying layer of polyimide. Two etchant formulations were identified which exhibited large etch rates at elevated temperatures and low enough background etch rates (approximately 1 μm/hr at 0 °C) to be useful in practical applications.