Copper on-chip interconnections: A breakthrough in electrodeposition to make better chips

Abstract

Copper on-chip interconnections represent not only a change in materials but also new ways of integration and depositing the conductor metal. Copper interconnections are superior to Al(Cu) interconnections because of the decreased resistance, improved reliability and reduced process complexity. Electrodeposition has played a key role in making implementation of the technology possible because it can deposit copper in Damascene structures without defects such as seams or voids. This unique property of electrodeposition is due to a phenomenon called "super-filling," in which the rate of the copper deposition reaction increases down into a feature as a result of the differential inhibition of the reaction kinetics by the additives present in the plating solution. Because of its unique advantages and superior performance, electrodeposition is being adopted by the entire semiconductor industry as the method of choice for depositing the copper conductor for on-chip interconnections.