CMP Process Optimization for Bonding Applications

This paper presents the optimization of a CMP process optimization in order to obtain very good bendability of copper patterned wafers. Copper planarization allowed obtaining low roughness, very smooth surfaces with practically no dishing for copper lines as wide as 500 micrometer. Polishing under optimized conditions process allowed highly improved bonding quality, as shown by Scanning Acoustic Microscopy and Transmission Electron Microscopy. Finally, the electrical behavior of direct copper bonded pad was analyzed, and on a 10x10 micrometer contact pad a specific resistance of rhoc= 0.98 Omega.micrometer2 was measured after a 200° C annealing for 30 minutes. Keywords: Planarization, TSV, Bonding, 3D, dishing, erosion, design rules