| 摘要 |
PURPOSE:To enable target pattern to be made in almost all the processes for manufacturing semiconductors by detecting interferring light from the coming on two light paths due to the variation in thickness of insulating film. CONSTITUTION:The light having come out of a light source 8 is linearly polarized by passing through a polarizing plate 9. When applied to a Normarsky prism 14 after reflected by a half-mirror 13, this linear polalization is separated into two light whose oscillation planes are orthogonal with each other. The light is projected to a target on the surface of a semiconductor substrate 17 after passing through a lens 15 and a photo-mask 16. Since the target has a step portion formed of Si oxide film, the two light cause a difference in phase due to that between light paths after reflection. Further, the two light are combined into one light by the prism 14, generates interferring light when passing a polarizing plate 12, and reaches a photoelectric conversion element 10. The element 10 can be informed of the position of the target by detecting the interference of the interferring light. Thereby, detection becomes possible at the target pattern made only of the step portion of Si film without any Si step portion. |
