| CPC G03F 7/70341 (2013.01) [G01F 23/14 (2013.01); G03F 7/70525 (2013.01)] | 14 Claims |

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10. A method for detecting liquid leakage in a liquid storage tank of a lithography system, wherein the lithography system comprises:
an immersion lithographic apparatus;
a fluid supply device configured to supply liquid to the immersion lithographic apparatus, and comprising at least one liquid storage tank, an upper liquid pipe and a lower liquid pipe connected to the liquid storage tank; and
a sensor comprising at least one hydraulic pressure gauge, wherein the at least one hydraulic pressure gauge is arranged near a lower part of the liquid storage tank, and connected to the lower liquid pipe and the upper liquid pipe,
wherein the method comprises:
measuring a hydraulic pressure at a bottom of the liquid storage tank of the liquid supply device with the hydraulic pressure gauge, wherein the liquid supply device is configured to supply liquid to the immersion lithographic apparatus; and
calculating a height of a liquid level from the hydraulic pressure at the bottom of the liquid storage tank.
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