| 摘要 |
PURPOSE:To simplify the structure of an alignment optical system and to cope with a change in mark position by separating a diffracted beam of 0th order and a diffracted beam of high order, which are generated by an alignment mark by irradiation with a light beam, through an objective system, and guiding them to a photoelectric detector. CONSTITUTION:The alignment mark RM is composed of a diffraction grating and the objective system consisting of an objective 21A, a bifocal element 21B, etc., moves corresponding to the change in the mark position; and light information from the alignment mark is sent to a phase detection system 40 through the objective optical system. When the diffracted beam of 0th order (regularly reflected light) and diffracted beam of high order (e.g. primary light) of the light information generated by the alignment mark are guided to a phase detector 40 through the objective optical system, the objective optical system is moved and controlled within the range wherein the diffracted beam of 0th order and the diffracted beam of high order are separated from each other at the light beam waist position BW of a light transmission side or at a nearly conjugate nearby position. Therefore, the need for a special optical path length correction optical system is eliminated. |
