Two-fluid nozzle for cleaning substrate and substrate cleaning apparatus

A two-fluid nozzle for cleaning substrates which mixes gas and liquid internally and injects liquid droplets with gas so as to clean a substrate, comprising:

• a gas supply passage for supplying gas, a liquid supply passage for supplying liquid, and a lead-out passage for leading out internally-formed liquid droplets which are formed by internally mixing gas and liquid,
• wherein said gas supply passage and said liquid supply passage open toward an entrance of said lead-out passage which is formed at a rear end of said lead-out passage, and mix the gas and the liquid in the vicinity of said lead-out passage entrance,
• wherein an injection port for injecting liquid droplets to the outside is formed at the front end of said lead-out passage,
• wherein a transition between the lead-out passage and the injection port is step-wise such that a cross-sectional area Sb of said injection port is smaller than a cross-sectional area Sa of said lead-out passage,
• wherein a cross-sectional area Sc of an exit of said gas supply passage is smaller than the cross-sectional area Sa of said lead-out passage,
• wherein said lead-out passage is formed in a straight shape,
• wherein the cross-sectional area Sb of said injection port is constant from an entrance thereof at the step-wise transition to an exit thereof and
• wherein the cross-sectional area Sc of the exit of said gas supply passage is equal to the cross-sectional area Sb of said injection port or smaller than the cross-sectional area Sb of said injection port.