Method and apparatus for detecting defects

A defect detecting apparatus comprising:

• a rotating table on which a substrate to be tested can be mounted and which can be rotated together with said substrate;
• a laser source for emitting a laser beam;
• illumination means having a polarization adjusting portion for adjusting the polarized state of said laser beam emitted from said laser source, a beam expander for expanding the diameter of said laser beam adjusted in said polarized state, and a beam shaping portion for shaping said diameter-expanded laser beam to have a shape that is long in one direction, said illumination means being disposed to obliquely irradiate said laser beam of said shape onto the surface of said substrate so that said one direction in which said shape is long can be substantially matched to a straight line running toward the rotation center of said substrate;
• image formation optical means for forming an image of scattered light from said substrate surface illuminated by said illumination means;
• image detection means for detecting said image of said scattered light from said substrate surface that is formed by said image formation optical means;
• and
• image processing means for processing an image signal detected from said optical image by said image detection means so as to detect defects on said substrate surface, wherein said illumination means further comprises an illumination intensity distribution flattening portion by which at least the area detected by said image detection means, of the area illuminated by said illumination means with said laser beam of which the intensity distribution is long in said one direction, can be uniformly illuminated with substantially the same illumination intensity.

A defect detecting method comprising the steps of:

• emitting from a laser source a laser beam having a Gauss distribution in its illumination intensity;
• shaping said laser beam from said laser source to have a flat distribution in its illumination intensity;
• focusing and irradiating said shaped laser beam of said flattened distribution onto a substrate to be tested;
• focusing scattered light from said substrate as a result of said irradiation of said laser beam, receiving said focused scattered light by a detector, and converting it by said detector into a signal;
• and
• processing said converted signal so as to detect defects on said substrate.