Substrate defect inspection method and substrate defect inspection apparatus

A substrate defect inspection method comprising steps of:

• irradiating a target substrate with an EUV beam emitted from an EUV illumination source by using a first focusing optical system;
• guiding a scattered reflected beam, but no specularly-reflected beam, among beams reflected from the target substrate irradiated with the EUV beam to a light receiving surface of a sensor by using a second focusing optical system;
• and
• determining that a defect is present at an irradiation spot of the target substrate with the EUV beam when an intensity of the scattered reflected beam received by the light receiving surface of the sensor exceeds a predetermined threshold,
• wherein the substrate defect inspection method comprises, before the irradiation of the target substrate with the EUV beam:
• a reflectance acquisition step of acquiring a reflectance of the target substrate to the EUV beam;
• and
• a threshold computation step of setting the predetermined threshold based on the reflectance acquired in the reflectance acquisition step.