Apparatus and Method for Inspecting Defects

A defect inspection apparatus comprising:

• an irradiation optical system that focuses a beam flux emitted from a laser light source and formed into a slit-shaped beam by fluxes of light that are substantially parallel in a longitudinal direction, from a direction having a required inclination with respect to a surface of a substrate to be inspected, so as to irradiate the beam flux onto the surface of the substrate to be inspected;
• a detection optical system that detects light from the substrate that has been irradiated with the slit-shaped beam;
• and
• a signal processor that processes a signal output from the detection optical system;
• wherein the irradiation optical system includes:
• a cylindrical lens for focusing the beam flux that has been emitted from the laser light source onto the substrate to be inspected, as the slit-shaped beam;
• wherein the cylindrical lens is disposed so as to obtain a distance between an incidence surface or emitting surface thereof and the slit-shaped beam upon the substrate to be inspected to be equal to a focal distance of the cylindrical lens.