Rezirkulierendes chemisches Bad mit Zufluss und selbstausgleichendem Abfluss

摘要

A chemical bath (11) in which batches of integrated circuit wafers (12) or other articles are immersed in hot liquid chemical during manufacture has a processing vessel (16), an adjacent sump vessel (22) and a trough (18) which carries overflow from the processing vessel (16) to the sump vessel (22). A pump (46) continuously recirculates liquid from the sump vessel (22) to the processing vessel (16) through a filter (48). A continuous inflow of liquid is received from a liquid chemical source and an intermittent outflow occurs through an outlet (54) at an upper region of the sump vessel (22). The liquid chemical source may, for example, supply make-up fluid or be a reprocessor that repurifies the outflow from the sump vessel (22). The storage capacity of the sump vessel below the outlet (54) is greater than that needed to contain the volume of liquid that is displaced in the processing vessel (16) by the batch of wafers (12). This avoids pump starvation when liquid level is lowered in the processing vessel (16) by removal of a batch of wafers (12) 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.