Substrate processing apparatus and processing cup cleaning method

A processing cup cleaning method comprising:

• a chemical liquid supplying step of horizontally holding a substrate, rotating the substrate around a vertical rotational axis passing through a central portion of the substrate, and discharging a chemical liquid toward the substrate;
• a first liquid receiving step of causing the chemical liquid, expelled outward from the substrate, to be caught by a guard that includes a cylindrical portion surrounding the substrate;
• a first supplying step of causing the chemical liquid, guided downward by the guard, to be caught by a cup, defining a liquid receiving groove of annular shape that is positioned below the cylindrical portion, and meanwhile draining the chemical liquid in the liquid receiving groove via a drain port provided in the liquid receiving groove;
• a cleaning liquid discharging step of causing a spin base, disposed under the substrate, to rotate around the rotational axis after the chemical liquid supplying step and meanwhile causing a first cleaning liquid nozzle to discharge a cleaning liquid, differing from the chemical liquid, above the spin base;
• a second liquid receiving step of causing the cleaning liquid, expelled outward from the spin base, to be caught by the guard;
• a second supplying step of causing the cleaning liquid, guided downward by the guard, to be caught by the liquid receiving groove of the cup;
• an accumulating step of accumulating the cleaning liquid in the liquid receiving groove by making a supply flow rate that represents a flow rate of the cleaning liquid supplied from the first cleaning liquid nozzle to the liquid receiving groove via the spin base and the guard, greater than a drain flow rate that represents a flow rate of the cleaning liquid drained from the liquid receiving groove via the drain port;
• and
• an immersing step of lowering the guard to immerse a lower end portion of the cylindrical portion in the cleaning liquid in the liquid receiving groove.