Electroless deposition of CoWP: Material characterization and process optimization on 300 mm wafers

The use of copper as a metal for interconnections has driven the apparition of new technological solutions. Selective barriers against copper diffusion deposited by electroless reaction bring interests in term of electromigration. In this article, CoWP electroless barriers deposited in a 300 mm Semitool Raider equipment are studied. Good uniformity for a standard thickness of 15 nm is demonstrated. Different growth rates of the barrier as a function of copper grain orientation are observed. The composition of the barrier is constant throughout the film. The deposition is selective, but corrosion phenomena and a superficial metallic contamination on the interline dielectric are revealed. The selectivity of the process is confirmed electrically for 12 nm thick barriers. The impact of copper corrosion on line resistance is addressed through preclean optimization.