To provide a wafer cleaning method capable of restricting breakage of fine structures disposed on a wafer, and a spin cleaning apparatus enabling such cleaning. The spin cleaning apparatus injects a cleaning liquid on a wafer surface while moving a nozzle, and at the same time, with an ultrasonic wave generated inside the nozzle, irradiates a cleaning liquid collision spot, thereby cleaning the wafer surface. The above apparatus includes at least one of the following functions: (1) a function of varying the rotation frequency of the wafer; (2) a function of varying the traveling speed of the nozzle in the direction parallel to the wafer; (3) a function of varying the output of the ultrasonic wave; and (4) a function of varying the distance between the nozzle and the cleaning liquid collision spot, all corresponding to the position of the cleaning liquid collision spot on the wafer.

 
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> Reverse osmosis system with control based on flow rates in the permeate and brine streams

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