Foreign matter removal method and storage medium

A computer-readable storage medium storing a program for causing a computer to execute a foreign matter removal method in which foreign matter attached to a substrate is removed using a foreign matter removal apparatus including a mounting stage adapted to rotate with a substrate mounted thereon, a laser light irradiation unit adapted to irradiate foreign matter removal laser light onto an edge of the substrate rotating on the mounting stage to remove foreign matter attached to the substrate, and a laser light-receiving unit adapted to detect power of the laser light irradiated from the laser light irradiation unit, the foreign matter removal method comprising:

• an irradiation step in which the laser light irradiation unit irradiates misalignment measurement laser light onto the edge of the rotating substrate mounted on the mounting stage;
• a power detection step in which, of the irradiated misalignment measurement laser light, remaining laser light other than the laser light blocked by the edge of the substrate is received by the laser light-receiving unit, and power of the laser light is detected;
• a rotation angle detecting step of detecting a rotation angle of the rotating substrate;
• a calculation step of calculating an amount of misalignment of the substrate based on data on the power of the misalignment measurement laser light detected in said output detecting step and data on the rotation angle detected by said rotation angle detecting step;
• a correction step of correcting for the misalignment of the substrate based on the calculated amount of misalignment;
• and
• a decomposition step in which, after the misalignment has been corrected for, said laser light irradiation unit irradiates foreign matter removal laser light onto the edge of the substrate, and a process gas that is to react with the foreign matter is jetted to the edge of the substrate so that the foreign matter attached to the substrate is decomposed and removed.