(115e) Study of Copper and Nanoparticles Interactions in CMP Wastewater and Their Pre-Treatment Using Filtration

Chemical-mechanical planarization (CMP) wastes pose a challenge in design of treatment schemes due to varied and proprietary slurry chemistries. The CMP process, a critical step in semiconductor fabrication, involves planning and smoothing a wafer surface by chemical and mechanical forces. The copper-CMP (cu-CMP) wastewater studied contains copper which must be removed before disposal or recycle. CMP wastewater contains inorganic and organic contaminants derived from the slurry, the wafer planarization and post-CMP cleaning processes. It was observed that cu-CMP samples are a very complex mixture of components of copper (II) ions in solution and onto Si and/or Al nanoparticles and the solubility is pH dependent. The focus of the present studies was on properties of CMP wastewater, copper in CMP slurry samples, the interactions between the nanoparticles and the copper, and the removal of particles and copper from effluents. Polishing slurries consist of 5 to 10 percent of very fine particles; surfactants are added to slurries to maintain good stability of the suspended solids in the slurry. The slurries are characterized according to: pH, turbidity (indicative of particle content), particle size distribution, metal ion content, suspended solids, dissolved solids, and chemical oxygen demand. A significant reduction of copper and turbidity was observed. The effluent without copper and particles can be reused in slurry dilutions. Also, the treated CMP effluent can further be treated to remove organics and particles from water, the latter treated via a filtration technique.