Apparatus for treating substrate and method for treating substrate

An apparatus for treating a substrate, the apparatus comprising:

• a liquid treating chamber treating a substrate by supplying a liquid to the substrate;
• a high-pressure chamber providing a treating space where a process of treating the substrate is performed by using a process fluid;
• a fluid supplying source providing the process fluid to the high-pressure chamber;
• a supply line connecting the high-pressure chamber and the fluid supplying source;
• a first valve and a second valve sequentially installed along a direction from the fluid supplying source to the high-pressure chamber on the supply line;
• a branch line branching from the supply line between the first valve and the second valve and connected to an exhaust line;
• a third valve installed on the branch line;
• an exhaust unit exhausting the process fluid inside the high-pressure chamber;
• a transfer robot transferring the substrate between the liquid treating chamber and the high-pressure chamber;
• and
• a controller,
• wherein the controller is configured to perform,
• before the transfer robot transfers the substrate to the high-pressure chamber for treating the substrate,
• a first operating of opening the first valve, and closing the second valve and the third valve, and
• a second operating of closing the first valve and the second valve, and opening the third valve to exhaust the remaining process fluid inside the supply line.