Patent ID: 7064821

Claim:
A method for detecting a defect at a region on a surface of a substrate and for discriminating between particle defects and subsurface defects, the method comprising: directing a first beam of polarized light to impinge at said region on the surface at a first incident angle relative to a direction normal to the surface; collecting scattered light caused by the first beam over a predetermined area and integrating the intensities of the scattered light over said area to form a first integrated response; directing a second beam of P-polarized light to impinge at said region on the surface at a second incident angle relative to a direction normal to the surface and where the second incident angle is greater than the first incident angle; collecting scattered light caused by the second beam over said area and integrating the intensities of the scattered light over said area to form a second integrated response; and comparing the first and second integrated responses to determine whether a defect is a particle or a subsurface defect.