MASKLESS PATTERNING OF GOLD ELECTRICAL CONTACTS BY LASER PLATING IN AFLOWING SOLUTION

Fine gold spots and lines for electrical contacts were deposited from a flowing plating solution under argon laser irradiation. The effects of cathode potential, laser power, and solution flow rate were studied on deposition rate and controllability of deposited pattern size. In situ observation revealed that vigorous boiling occurs under solution flow conditions and that laser plating is enhanced by a strong microst irring due to the ejection of bubbles. Gold electrical contacts of sim ilar to 1 mu m height are produced in less than 0.5 s for spots, and a t a laser beam scan speed of more than several hundreds of mu m/s for lines at a laser power of several watts. The diameter of the spots and the width of the lines are controlled by laser power and cathode pote ntial, as well as by laser beam diameter, at less than 100 mu m. Such laser plated spots and lines have a fine morphology, a high adhesion t o the substrate, and a low electrical resistivity of 5-15 mu Omega . c m.