The Evolution of Surface Roughness of Copper Electrodeposition Directly on Ultra-Thin Air Exposed TaN Layers

Abstract

Surface roughness of both seed layers and electrodeposited copper for ULSI interconnects affect adhesion and fracture characteristics of the electrodeposited plate. In this program experiments were performed on copper, deposited from complexing citrate baths, directly onto TaN barrier layers, as a function of copper thickness (as measured by plating time) and subsequent annealing. It has been shown that surface roughness increase with increasing plate thickness, reaching a constant roughness at a thickness of about 350 nm. Annealing, in order to enhance plate resistivity, has no appreciable effect on surface roughness.