Patent ID: 8347901

Claim:
A substrate cleaning system comprising: a cleaning tank that contains a cleaning liquid and accommodates a semiconductor wafer in an upstanding manner; an ultrasonic generator that generates ultrasonic waves in the cleaning liquid contained in the cleaning tank from therebelow while the semiconductor wafer is kept upstanding; a first supply pipe connected to the cleaning tank so as to supply a first cleaning liquid, having a gas dissolved therein, into the cleaning tank from therebelow; a second supply pipe connected to the cleaning tank separately from the first supply pipe so as to supply into the cleaning tank from therebelow a second cleaning liquid having the gas dissolved therein at a dissolved gas concentration different from the dissolved gas concentration of the first cleaning liquid; and a control device for controlling a flow rate of the first cleaning liquid supplied into the cleaning tank, a flow rate of the second cleaning liquid supplied into the cleaning tank, and the generation of ultrasonic waves by the ultrasonic generator to clean the semiconductor wafer while the liquids are being supplied into the cleaning tank and are overflowing from an open upper end of the cleaning tank, the control device being programmed to cause, while the semiconductor wafer is being cleaned, the ultrasonic generator to generate ultrasonic waves for a period of time, then stop the generation of ultrasonic waves for an intermission, and then, during the intermission, reduce the dissolved gas concentration of the cleaning liquids contained in the cleaning tank, or to cause, while the semiconductor wafer is being cleaned, reduction in the dissolved gas concentration of the cleaning liquids contained in the cleaning tank while ultrasonic waves continue to be generated by the ultrasonic generator in the cleaning liquids.