With the goal of optimizing point-to-point etch uniformity in a continuous flow wet processing system, a comprehensive fluid dynamics study was undertaken. Aspects of this work included developing a computational, finite-element, fluid dynamic model; performing a series of empirical studies based on dye-injection with photo detection and video analysis; and observing platinumwire bubble generation with transparent wafers.
Various flow modification designs were tested including the base case of no inserted device, a stationary “spinner” insert, and a stationary “showerhead” insert. Unsteady, non-uniform, flow distribution and zones of substantial flow recirculation were observed in the case of using no flow modification device. These observations were confirmed with the computational fluid dynamic model.
Used in conjunction with the two different types of flow inserts, a new supplementary Teflon screen was designed and tested. The combined optimum configuration using this screen with an insert was then identified. Significantly enhanced point-to-point etch uniformity, with minimal recirculation and prompt fluid displacement, resulted from this design.