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A flow control system in an apparatus for treating a work piece controls a flow rate of treatment liquid dispensed from a liquid dispenser. The system includes a flow meter that measures a flow rate of liquid being supplied to the liquid dispenser, a controller that receives signals indicative of a

A flow control system in an apparatus for treating a work piece controls a flow rate of treatment liquid dispensed from a liquid dispenser. The system includes a flow meter that measures a flow rate of liquid being supplied to the liquid dispenser, a controller that receives signals indicative of a flow rate measured by the flow meter, and a pressure regulator that regulates pressure of the liquid supply downstream of the flow meter based on control signals from the controller. At least two alternative liquid supply paths are provided downstream of the pressure regulator and upstream of an outlet of the liquid dispenser. Each supply path is equipped with a respective shutoff valve and provides a respectively different pressure drop to the treatment liquid.

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1. Apparatus for treating a work piece, comprising: a holder configured to hold the work piece in a predetermined orientation;a liquid dispenser positioned relative to said holder so as to dispense a treatment liquid onto a surface of the work piece when positioned on said holder; anda flow control

1. Apparatus for treating a work piece, comprising: a holder configured to hold the work piece in a predetermined orientation;a liquid dispenser positioned relative to said holder so as to dispense a treatment liquid onto a surface of the work piece when positioned on said holder; anda flow control system that controls a flow rate of treatment liquid dispensed from said liquid dispenser, said flow control system comprising a flow meter that measures a flow rate of liquid being supplied to said liquid dispenser, a controller that receives signals indicative of a flow rate measured by said flow meter, a pressure regulator that regulates pressure of the liquid supply downstream of the flow meter based on control signals from said controller, and a plurality of liquid supply paths downstream of the pressure regulator and upstream of an outlet of said liquid dispenser, each of said plurality of liquid supply paths being equipped with a respective shutoff valve, wherein the controller is configured to select an appropriate one of shutoff valves with all of the remaining shutoff valves being kept closed to provide a respectively different pressure drop to liquid when passing through a respective one of said plurality of liquid supply paths. 2. The apparatus according to claim 1, wherein said flow meter is an ultrasonic flow meter. 3. The apparatus according to claim 1, wherein said pressure regulator comprises a valve chamber delimited by inner surfaces of a pair of diaphragms and upper and pneumatically controlled pressure chambers delimited by respective outer surfaces of said pair of diaphragms. 4. The apparatus according to claim 1, wherein said flow control system further comprises an electro pneumatic converter receiving control signals from said controller based upon readings of said flow meter and pneumatically controlling said pressure regulator based upon the control signals received from said controller. 5. The apparatus according to claim 1, wherein each of said shutoff valves is a solenoid-actuated diaphragm valve controlled by signals issued from said controller. 6. The apparatus according to claim 1, wherein said flow control system comprises at least three of said liquid supply paths. 7. The apparatus according to claim 1, wherein said at least two alternative liquid supply paths comprise conduits of a same diameter each communicating with corresponding orifices of respectively different diameters. 8. The apparatus according to claim 1, wherein said plurality of liquid supply paths comprise conduits of respectively different diameters. 9. The apparatus according to claim 1, wherein said holder is a spin chuck in a process module for single wafer wet processing of semiconductor wafers. 10. The apparatus according to claim 1, wherein said flow meter is contained within a first module mounted within a wet chemical treatment region of said apparatus, said controller is contained within a second module mounted within an electronics cabinet of said apparatus, and said pressure regulator and said shutoff valves are contained within a third module mounted within said wet chemical treatment region of said apparatus. 11. A flow control system for controlling a flow rate of treatment liquid dispensed from a liquid dispenser in an apparatus for treating a work piece, said flow control system comprising: a flow meter that measures a flow rate of liquid being supplied through a conduit;a controller that receives signals indicative of a flow rate measured by said flow meter;a pressure regulator that regulates pressure of a liquid supply downstream of the flow meter based on control signals from said controller; anda plurality of liquid supply paths downstream of the pressure regulator, each of said plurality of liquid supply paths being equipped with a respective shutoff valve, wherein the controller is configured to select an appropriate one of shutoff valves with all of the remaining shutoff valves being kept closed to provide a respectively different pressure drop to liquid when passing through a respective one of said plurality of liquid supply paths. 12. The flow control system according to claim 11, wherein said flow meter is an ultrasonic flow meter, and wherein said pressure regulator comprises a valve chamber delimited by inner surfaces of a pair of diaphragms and upper and pneumatically controlled pressure chambers delimited by respective outer surfaces of said pair of diaphragms. 13. The flow control system according to claim 11, wherein said flow control system further comprises an electro pneumatic converter receiving control signals from said controller based upon readings of said flow meter and pneumatically controlling said pressure regulator based upon the control signals received from said controller. 14. The flow control system according to claim 11, wherein each of said shutoff valves is a solenoid-actuated diaphragm valve controlled by signals issued from said controller. 15. The flow control system according to claim 11, wherein said flow meter is contained within a first module, said controller is contained within a second module, and said pressure regulator and said shutoff valves are contained within a third module.