| 摘要 |
PURPOSE:To accurately detect foreign matters by providing a first and second lighting systems which respectively illuminate the surface and rear of a photomask and a first and second detecting system which respectively detect foreign matters on the surface and rear of the photomask. CONSTITUTION:At the time of detecting foreign matters on the surface 30a of a light intercepting pattern, lighting light having a wavelength l from a light source 1A is reflected by the surface 30a through a lens system 3A, half mirror 5A, and lens 6A and is made incident to a prism 10A. Since the prism 10A transmits the light having the wavelength lambda1, the light is transmitted to a control section 100 after photoelectric conversion at a photodetector 8A. Another lighting light 1B having a wavelength lambda2 from another light source 1B passes through the surface 30a and is transmitted to the section 100 after the light is reflected by the prism 10A and subjected to photoelectric conversion at another photodetector 9A. When foreign matters 71 and 72 respectively adhere to a light intercepting pattern 81 and transmitting section 82, the reflection output R1 of the element 8A becomes lower than that by the pattern 81 due to the matter 71 and the transmission output T1 of the element 9A becomes lower than that by the section 81 due to the matter 72. A resultant output I1 is obtained by combining the output obtained by cutting off the output R1 lower than a slice level SL1 and the output T1. |
