| 摘要 |
<p>PURPOSE:To surely detect an alignment mark with a simple structure by arranging the light receiving surface of a first light receiving element nearly perpendicularly to the optical axis of reflected light from the surface of a planar object and the light receiving surface of a second light receiving element nearly perpendicularly to the optical axis of returning light toward a light source from the nearly vertical surface of the alignment mark. CONSTITUTION:The title detecting device 1 is constituted of a light source 2 which emits light at a prescribed angle from an obliquely upper position of a wafer 10, first light receiving element 3 the light receiving surface 3a of which is perpendicularly faced to the optical axis 2b of reflected light from the surface of the wafer 10a, and second light receiving element 4 the light receiving surface 4a of which is nearly perpendicularly faced to the optical axis 2c of returning light toward the light source 2 from the nearly vertical surface 11a of an alignment mark 11. The device 1 finds the position of the mark 11 from the position of the device 1 which moves within a fixed period of time and the difference between the light detecting signals of the elements 3 and 4. Therefore, the position of the mark 11 can be surely detected with a simple structure.</p> |
