Patent ID: 7857961

Claim:
A method of electroplating copper on a substrate comprising: a) providing a copper electroplating solution comprising copper ions, electrolytes, chloride ions and bromide ions, the concentration of the chloride ions and the bromide ions in the copper electroplating solution fulfill the relationship in the following equations: 3≦Br≦6 (6) 30≦Cl (7) wherein the Cl is the concentration of the chloride ions in mg/l in the copper electroplating solution and the Br is the bromide ion concentration in mg/l in the copper electroplating solution; b) placing a positive electrode in the copper electroplating solution; c) placing the substrate as a negative electrode in the copper electroplating solution; d) applying an electrical current through the copper electroplating solution and the positive and negative electrodes; and e) electroplating a copper metal layer on the substrate, the copper metal layer is 20 μm or less thick.