Substrate treatment device and substrate treatment method

A substrate treatment apparatus comprising:

• a substrate treatment unit that treats a substrate with a treatment liquid containing ozone dissolved therein;
• a recovery tank in which the treatment liquid discharged from the substrate treatment unit is recovered;
• a recovery pipe that connects the substrate treatment unit to the recovery tank;
• a heater that heats the treatment liquid to a first temperature in at least one of the recovery pipe and the recovery tank;
• a supply piping system that supplies the treatment liquid from the recovery tank to the substrate treatment unit;
• an ozone gas pipe that supplies ozone gas to the supply piping system to mix the ozone gas in the treatment liquid passing through the supply piping system;
• an ozone concentration meter that detects an ozone concentration of the treatment liquid in the recovery tank or an ozone concentration in a space contacting a liquid surface of the treatment liquid in the recovery tank;
• a switch valve that switches on and off flow of the treatment liquid from the recovery tank to the supply piping system;
• and
• a controller that controls the switch valve based on a detection result of the ozone concentration meter;
• wherein the controller opens the switch valve if the concentration detected by the ozone concentration meter is not higher than a predetermined threshold, and closes the switch valve if the detected concentration is higher than the predetermined threshold.