| 摘要 |
PURPOSE:To enable alignment to be carried out with high precision, by dividing objectives of an alignment optical system into front and rear groups and arranging a mirror midway between the front and rear groups for bending an optical axis. CONSTITUTION:Light from a halogen lamp is collected by a collection mirror and a collection lens and reaches a front group of objectives 31 via a half prism 25, a rear group of objectives 26 and a mirror 27. When the driven components (26, 27 and 31) come to the position of an alignment mark provided by a latent image formed on the surface of a wafer, the light is applied to the position of the alignment mark. If the objectives are not divided, a much larger mirror for bending the optical axis as indicated by 27', would be required for detecting with high NA. In order to avoid this problem, the objectives are divided into two groups and the bending mirror 27 is inserted at a position in a flux of light where light beams are as parallel as possible. Thus, detection with high NA is enabled by dividing the objectives into two groups while disposing the front groups of objectives 31 closer to the wafer 4. |
