Effects of Seeding Layers on Electroless Copper Deposition

Abstract

AbstractCopper has been actively pursued as the most promising candidate for replacing the current Al metallization for ULSI interconnection because of its higher electrical conductivity and resistance to electromigration. In this work, we present our experimental results on electroless copper deposition on various seeding layers from a formaldehyde-based solution with EDTA as a complexing agent. For electroless plating, a seeding layer is essential for the initiation of copper deposition. X-ray diffraction analysis revealed a variation in the crystallographic orientation of the electroless deposited copper with different underlying seeding layers. The seeding layer is the key factor affecting copper nucleation and grain growth. The initial nucleation behaviors of electroless copper deposition on palladium and copper seeding layers were investigated. The microstructure of electroless deposited copper blanket films was studied using both SEM and AFM, and the crystallinity was analyzed using XRD. The crystal orientation and surface texture of the electroless deposited copper films could be modified by thermal annealing in vacuum (10E-6 Torr) for 30 min at temperatures ranging from 200°C to 300°C. The ratio of crystal orientation, I(111)/I(200) increased with higher annealing temperature, indicating enhanced growth of the (111) crystal structure.