Importance

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Abstract

A chemical bath in which batches of integrated circuit wafers or other articles are immersed in hot liquid chemical during manufacture has a processing vessel, an adjacent sump vessel and a trough which carries overflow from the processing vessel to the sump vessel. A pump continuously recirculates liquid from the sump vessel to the processing vessel through a filter. A continuous inflow of liquid is received from a liquid chemical source and an intermittent outflow occurs through an outlet at an upper region of the sump vessel. The liquid chemical source may, for example, supply make-up fluid or be a reprocessor that repurifies the outflow from the sump vessel. The storage capacity of the sump vessel below the outlet is greater than that needed to contain the volume of liquid that is displaced in the processing vessel by the batch of wafers. This avoids pump starvation when liquid level is lowered in the processing vessel by removal of a batch of wafers and also assures that outflow matches inflow from the liquid chemical source over a period of time without requiring flow sensing devices, dynamic valving or other complications.

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First Claim