| 摘要 |
PURPOSE:To measure a step without contacting by providing a variable wavelength light source, a photodetector and an arithmetic processing part, a means which cuts off diffracted light of degree zero or light other than the diffracted light of degree zero, etc., so as to cause interference. CONSTITUTION:A sample 44 is irradiated with light having proper wavelength. Further, a spatial filter 12 is moved to a position 11 and the sample 44 is observed through an ocular 32. Then, a scale plate 30 associated with a spatial filter 22 is moved to put a measurement position within a mark 31. The filter 12 is moved to its original position and its position is adjusted precisely. The light illuminating the sample 44 reaches the surface of the spatial filter 21 the rough a lens 19. At this time, the diffracted light of degree zero is cut off by the filter 21 and only diffracted light reaches the filter 22. Then, the signal of the photodetector 23 is inputted while the wavelength of the irradiation light is varied and this light is converted photo electrically and processed by a microcomputer 39. This processing corrects spectral characteristics of the light source 2, lens system, and optical system firstly. Then, wavelengths with which the maximal and minimal values of variation in interference intensity are obtained are found and the step is measured from an expression containing the found maximal and minimal values.
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