| 摘要 |
PURPOSE:To enable exact coincidence between the image surface of a projection optical system and the surface of a wafer by installing a specified reference reflection surface on a wafer stage, detecting a focus point by utilizing said reflection surface and with a TTL automatic focusing system, and positioning the wafer surface at an image surface position, by setting the focus position as a reference. CONSTITUTION:In a state where a reticle 7 having a circuit pattern is mounted on a stage 70, exposure light from illumination optical systems 1-6 is aimed at the reticle 7, and the light which has passed through the reticle 7 is aimed at the reference reflection surface 17 on a wafer stage 10, via a projection optical system 8. Reflected exposure light from the reference reflection surface 17 is again returned to the illumination optical system 1-6, and received by a photodetector 16. Based on the output signal from the photodetector 16, the position of the reference reflection surface 17 is changed, by moving the wafer stage 10 up and down in the optical axis direction of the projection optical system 8, and the position of the reference reflection surface 17 exhibiting the maximum value of the output signal from the photodetector is detected, thereby recognizing this position as the optimum forcus position of the projection optical system 8. |
