| 摘要 |
PURPOSE:To make it possible to perform external inspection under the illumination for dark field of view and automatic focal point adjustment simultaneously, by performing the external inspection and the automatic focal point adjustment by light beams having different wavelengths. CONSTITUTION:A first optical system projects a focal point detecting pattern 2 on a wafer 5 which is a material to be measured through a lens 4. A second optical system forms the image of the reflected pattern from the material to be measured 5 on a contrast detector 7' through a lens 4 and optical filters 3 and 13. A third optical system irradiates the light, whose wavelength is different from the wavelength region passing the optical filters 3 and 13, to the material to be measured 5 from the slant direction. The light for illuminating the dark field of view, which is generated by the third optical system comprising a light source 10 and parabolic concave mirrors 11 and 12, is stopped by the optical filters so as not to influence the contrast detector 7'. In this constitution, the external inspection and automatic focal point adjustment are simultaneously performed by the light beams having the different wavelengths. |
