Diode Laser-Assisted Deposition of Gold and Copper from Thin Organometallic Films

We have developed a simple, compact and economical diode laser-assisted process for the direct writing of gold and copper on polyimide. Gold precursor films were deposited by spin-coating a commercially available organometallic compound onto the substrate. The local pyrolysis of these films was induced by the focused beam of an AlGaAs diode laser array ( Pmax = 1 W, λ = 796 nm). Direct writing was achieved in open air while moving the substrate at speeds up to 15 mm/s. Gold lines 13–17 μm wide, ∼0.1 μm thick, and having a resistivity of 30 μΩ·cm, were obtained on polyimide with good reproducibility using writing speeds > 10 mm/s. Following a simple annealing process, these gold lines successfully activated the electroless plating of copper. After 45 min of plating, 2 μm thick Cu/Au conductors, having a resistivity of 8 μΩ·cm, were deposited. A commercially available copper precursor was also studied for the direct deposition of copper.