| 摘要 |
PURPOSE:To measure relative positions with relative position detection accuracy of 0.01 mum order which is not affected by variation of the gap between a mask and a wafer by providing a 1st body with the slit and a 2nd body with the grid opposite each other while the two bodies are set at a fine distance. CONSTITUTION:A linear diffraction grating 2 is formed on the wafer 1 at a grating pitch D+E to length C in the array direction and to the width B of the grid, and the mask 3 which has the slit 4 with width G and length F is provided above the wafer 1 opposite across the gap A. Incident light 5 which is transmitted without interferring with the slit 4 on the mask 3 is made incident directly on the linear diffraction grating 2 on the wafer 1, and reflected and diffracted, and reflected and diffracted light 6a of (-1)th order is used to detect the relative positions of the mask 3 and wafer 1. A photodetection sensor is placed in the optical path of the diffracted light 6a of (-1)th order passing through the slit 4 to detect variation in the quantity of light, so that the relative positions of the mask 3 and wafer 1 can accurately be measured. |
