Substrate treatment device

A substrate treatment device, comprising:

• a placement stand configured to rotate the substrate, the substrate including a first surface and a second surface opposite the first surface, the first surface facing the placement stand;
• a cooling part configured to supply a cooling gas into a space between the placement stand and the substrate;
• a first liquid supplier configured to supply a first liquid on the second surface of the substrate;
• a second liquid supplier configured to supply a second liquid on the second surface of the substrate, the second liquid being more conductive than the first liquid;
• and
• a controller controlling rotation of the substrate, supply of the cooling gas, supply of the first liquid, and supply of the second liquid,
• the controller being configured to perform following steps;
• a preliminary step of supplying the second liquid on the second surface of the substrate, a temperature of the second liquid being higher than a freezing point of the first liquid, and supplying the cooling gas into the space between the placement stand and the substrate,
• a liquid film forming step of forming a liquid film by supplying the first liquid toward the second surface of the substrate after the preliminary step,
• a supercooling step of putting the liquid film on the second surface of the substrate in a supercooled state, and
• a freezing step of freezing at least a part of the liquid film on the second surface of the substrate,
• in the liquid film forming step,
• after stopping the supply of the second liquid,
• rotating the substrate at a rotational speed of the preliminary step to discharge at least a part of the second liquid supplied to the second surface of the substrate,
• after discharging at least part of the second liquid, setting a first rotational speed slower than the rotational speed in the preliminary step, and then supplying the first liquid toward the second surface of the substrate, and
• in the freezing step, the liquid film has a layer comprising only the first liquid if the second liquid is completely discharged in the liquid film forming step, or the liquid film has a layer comprising the first liquid and the second liquid if a part of the second liquid is left in the liquid film forming step.