Substrate cleaning apparatus and substrate cleaning method

A substrate cleaning apparatus for cleaning a substrate by supplying a cleaning liquid, containing a plurality of liquid chemicals diluted with pure water, to the substrate, said apparatus comprising:

• a substrate holder configured to rotate a substrate;
• a pure water supply line provided with a pure water flow regulator and a pure water supply valve;
• a first chemical supply line provided with a first chemical flow regulator and a first chemical supply valve;
• a second chemical supply line provided with a second chemical flow regulator and a second chemical supply valve;
• a merging line including a meeting point therein at which pure water flowing through the pure water supply line, a first liquid chemical flowing through the first chemical supply line, and a second liquid chemical flowing through the second chemical supply line meet to form a cleaning liquid;
• a cleaning liquid supply line coupled to the merging line;
• a cleaning liquid supply nozzle coupled to the cleaning liquid supply line and configured to supply the cleaning liquid onto the substrate;
• and
• a controller configured to:
• (i) open the pure water supply valve while controlling the pure water flow regulator,
• (ii) open the first chemical supply valve based on a first opening delay time that has elapsed since the pure water supply valve has been opened while controlling the first chemical flow regulator, and
• (iii) open the second chemical supply valve based on a second opening delay time that has elapsed since the pure water supply valve has been opened, while controlling the second chemical flow regulator, the second opening delay time being longer than the first opening delay time,
• wherein the first opening delay time and the second opening delay time being set such that the pure water, the first liquid chemical, and the second liquid chemical all reach the meeting point simultaneously for a first time to form the cleaning liquid and such that a ratio of flow rates of the pure water, the first liquid chemical, and the second liquid chemical in the cleaning liquid, supplied from the cleaning nozzle, is constant from a beginning of the supply of the pure water, the first liquid chemical, and the second liquid chemical from the cleaning liquid supply nozzle.