Patent ID: 8454752

Claim:
A foreign substance removing method for removing foreign substances attached to a substrate by using a foreign substance removing apparatus including a mounting table for mounting and rotating a substrate and a laser beam irradiation unit for removing foreign substances attached to a surface of the substrate by irradiating a foreign substance cleaning laser beam onto the substrate mounted and rotated on the mounting table, the foreign substance removing method comprising: irradiating a laser beam for measuring an outer diameter of the substrate from the laser beam irradiation unit onto an end portion of the substrate mounted and rotated on the mounting table; detecting a light receiving output of the laser beam which is not blocked by the end portion of the substrate among the irradiated laser beam, by a laser beam receiving unit; detecting a rotation angle of the rotating substrate; calculating an outer diameter of the substrate and an amount of a positional deviation of the substrate based on the detected light receiving output and the detected rotation angle; moving the substrate to correct the positional deviation of the substrate based on the calculated amount of the positional deviation of the substrate; determining a range based on the calculated outer diameter of the substrate, for decomposing substances; and decomposing and removing the foreign substances attached to the surface of the substrate located within said range from an outer end portion of the substrate by injecting a processing gas that reacts with the foreign substances and irradiating the foreign substance cleaning laser beam having an elongate shaped irradiation cross section from the laser beam irradiation unit toward the surface of the substrate within the range.