| 摘要 |
PURPOSE:To measure the distance between a mask and a wafer by emitting a laser light to a very small gap formed between a knife edge on the mask and the surface of the wafer, and analyzing a diffraction pattern generated by the very small gap. CONSTITUTION:A knife-edge 2 on a mask 3 is formed by processing a silicon mask frame 1 through chemical anisotropic etching. An end face of the knife edge 2 is on the same plane as the surface of the mask 3. When a laser light 6 which is a coherent light is emitted to a very small gap 5, the laser light 6 is diffracted and a Fraunhofer diffraction pattern is detected at a place away from the gap 5. This Fraunhofer diffraction pattern is changed in accordance with the size of the gap 5, and therefore the size of the gap 5 can be measured by monitoring the Fraunhofer diffraction pattern by a first dimensional image sensor 7 and analyzing the pattern. |
