ENVR 107 |
| Copper is used extensively in semiconductor circuits as the multi-layer metal. One process that is repeated hundreds of times during fabrication is chemical mechanical planarization (CMP). In addition to copper, discharges from Cu-CMP processes often contain chelating agents such as EDTA (ethylenediaminetetraacetic acid) and citric acid and they tend to form copper-chelated anions. PEI-agarose adsorbents in a packed column are capable of removing these anions, but the competitive binding between these chelating agents and PEI for copper is not well understood and needs to be explored. This study investigates the binding of copper(II) ions and copper-chelated anions to PEI-agarose in packed column continuous experiments. The pH of the column is fixed to 5.5 using 0.1 M acetate buffer. The ratio of chelator to copper ions is varied. Copper binding capacity and copper breakthrough curves are compared and contrasted to results without additional chelators present. Excess EDTA in the solution results in almost no copper binding in the packed column, whereas excess citric acid in the solution enhances the copper binding. The contrasting adsorption behavior of EDTA-chelated copper(II) species and citric acid-chelated copper(II) species can be explained in terms of electrostatic interactions which influence the surface charge of the PEI as well as the charge property of EDTA-chelated copper(II) species and citric acid-chelated copper(II) species. The presence of these species in CMP waste streams significantly alters adsorption behavior. However, this waste treatment technique is still feasible for the semiconductor industry. |
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General Topics
2:00 PM-4:10 PM, Wednesday, August 22, 2007 Boston Park Plaza -- Beacon Hill Rm, Oral
Division of Environmental Chemistry |