| 摘要 |
PURPOSE:To detect the foreign matter on a substrate with good sensitivity by condensing laser beam to obliquely irradiate the surface of a substrate and condensing the scattering beam from the irradiated point by a first lens to intercept the same by the shading optical system provided on the Fourier transform surface of the lens. CONSTITUTION:It is supposed that a substrate is obliquely irradiated with laser beam 18 from above and a small spot is formed on foreign matter 36. The reflected beam from the foreign matter 36 is condensed by a lens 40 and separated from the reflected beam from a pattern by the shading plate placed above a Fourier transform surface 16 to be subjected to inverse Fourier transform by a lens 41. In this case, when a slit capable of passing through the conjugate point of the area where the foreign matter 36 is placed is provided, only the reflected beam from the foreign matter 36 is incident on a photodetector 34. The laser beam 18 is scanned in the direction vertical to the surface of space and the slit is also formed in an elongated shape in the direction vertical to the surface of the space in order to correspond to the scanning of the laser beam. By this constitution, the foreign matter on the substrate can be inspected without being affected by the circuit pattern formed on the substrate. |
