Improving Process Control for Copper Electroplating through Filter Membrane Optimization

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To achieve uniform copper plating on the surface of the wafer consistently in a production lot, a particle-free plating solution must be presented to the wafer under uniform pressure, uniform flow and at the proper formulation. This is accomplished by recirculating large volumes of the plating solution past the surface of the wafer. It is important that the chemistry of the solution remains uniform during the copper plating process to ensure repeatable performance. To maintain a low particle level, the fluid is filtered in a recirculated mode at a high flow rate. The filter must have low pressure drop, good particle retention and high throughput to result in low wafer defects and high system uptime. In addition, the proper filter must be selected so that it doesn’t absorb or remove desirable components like additives as it removes contamination from the solution.