HORIZONTAL POSITION DETECTING DEVICE

摘要

PURPOSE:To enable noncontact detection by arranging an irradiation optical system and a converging optical system so that their optical axes are symmetrical about the optical axis of a main objective and detecting the inclination the optical axis of the main objective in a conjugation area to the vertical. CONSTITUTION:A reticle 2 and a wafer 3 are arranged in conjugate relation about the projection objective 1 and the pattern on the reticle 2 is reduced and projected on the wafer 3. The irradiation optical system 10 supplies collimated light from a light source 11 into parallel luminous flux through an irradiation objective 14 and supplies light of different wavelength from exposure light onto the wafer 3, and its reflected luminous flux is converged 21 on a four-split photodetecting element 22. The slanting direction of the exposed area of the wafer 3 is detected from the position of the convergence point on the element 22 and a control means 31 generates a control signal corresponding to the direction and quantity of displacement of the convergence point on the element 22 and a driving means 32 corrects the inclination of the wafer 3. The irradiated area on the wafer 3 is made as large as the exposed area by the projection objective 1 to set the exposed area automatically at an accurate vertical position as to the optical axis 1a.