| 摘要 |
PURPOSE:To make it possible to efficiently conduct focusing operation in a short period of time without rearranging characteristics for every wafer and for every stage of process by a method wherein a focusing-detecting optical system, a monitor detecting optical system, a dividing means and a focusing-detecting means are provided. CONSTITUTION:The light, emitted from the light-emitting element 4 of a focusing- detecting optical system, is image-formed at the point P on a wafer 1 through a light- passing slit 6 and an image-forming lens 7, the reflected image is image-formed on a light-receiving element 12 through a vibration mirror 9 and a light-receiving slit 11. Also, the light, emitted from monitoring light emitting element 13 of a monitoring detection optical system, is image-formed at the point P by a lens 14, and the reflected image is received by a monitoring light-receiving element 16 through a lens 15. Then, the ratio of the output of the element 12 and the output of the element 16 are computed, the output of the element 12 is normalized, and the value of the dividing means is computed by conducting the focusing detection by phase-synchronized detection through a phase-synchronized detector 20. As a result, the focusing operation can be conducted quickly and efficiently without depending on the change of reflection rate of the wafer. |
