Wastewater Management Strategy for the Copper CMP Process
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The management of copper Chemical Mechanical Planarization (CMP) wastewaters generated in the copper metallization process has proven to be a significant challenge for the semiconductor industry. The challenge is driven by the waste constituents and volume: copper, an aquatic toxin; suspended slurries, which are difficult to remove from solution; organic additives, which can demonstrate toxicity and oxygen demand; and high volumes of water. IBM achieved effective management of this wastestream through chemical and water source reductions, installation of a segregated wastewater collection system, and implementation of an innovative microfiltration treatment system. Water and slurry use was reduced by 40% and 15% respectively on the CMP tools through improved process flows, slurry recirculation, and reduced idle flows. Tool drain systems were segregated to separate the slurry wastes and rinsewaters, reducing the CMP slurry wastestream volume by 50%. The slurry waste was collected through a dedicated drain system and routed to a microfiltration treatment system. The system reduces copper and solids concentration by over 99% and creates an effluent suitable for discharge to a receiving water or POTW or for further biological treatment to remove organic additives. The system is also capable of removing copper from plating solutions and rinsewaters. Effective, economic management of the treatment of the CMP wastestream was achieved by extensive collaboration between the process, equipment and environmental engineers. Implementation of this system in 2002 improved the stability of the overall wastewater treatment process and reduced the potential of exceeding discharge permit limits.