Investigating the Compatibility of Ruthenium Liners with Copper Interconnects

Abstract

Ruthenium is proposed as an alternative liner material in sub 30-nm line-width device technology. Ruthenium is a noble metal and does not oxidize readily. Hence, it is possible to directly plate copper on ruthenium. Because of very low solubility of copper in ruthenium, ruthenium also offers good barrier properties. However, the same noble electrochemical characteristics that prevent the oxidation of ruthenium and so useful for being able to directly plate copper provides challenges in terms of corrosion of copper lines in subsequent wet processing. Copper is electrochemically active to ruthenium. As a result of which, in a galvanic couple with ruthenium copper corrosion will be accelerated. In this paper we will examine the kinetics of galvanic corrosion using novel techniques of in-situ AFM analysis and demonstrate that through chemistry optimization, galvanic corrosion can be minimized.