Apparatus and method for regulating fluid flows, such as flows of electrochemical processing fluids

A method and apparatus for regulating fluid flows, such as flows of electrochemical processing fluids for processing microelectronic workpieces. The apparatus includes a valve body having an entrance port, an exit port, and a flow passage between the entrance and exit ports through which a first fluid flows. The valve body further includes a pressure chamber coupleable to a second fluid source and at least partially isolated from the flow passage. A regulator, movably disposed in the flow passage to change a flow area of the flow passage, has a first surface with a first projected area and a second surface with a second, larger, projected area, both of which are operatively coupled to the first fluid. A third surface of the regulator is operatively coupled to the second fluid. The regulator can adjust its position to maintain a constant or nearly constant first fluid flow rate as the fluid pressure at the entrance port changes.