Optical exposure apparatus of scanning exposure system and its exposing method

The present invention relates to an optical exposure apparatus of a scan-exposure system for transferring a pattern image formed on a reticle onto a wafer as the reticle and the wafer are relatively moved, and its exposing method, and more particularly to improvement of the reduction of a DOF (Depth of Focus) of a projection lens, which is caused by deformation of the reticle and upper and lower movement of the reticle at the time of scanning exposure. In an optical exposure apparatus of a scan-exposure system, scan-exposure is preliminarily executed before an actual scan-exposure, and a reticle position measuring device measures a positional change of a reticle in the upper and lower direction with the movement of a reticle stage to a scanning direction. Then, a calculation circuit obtains correction data for an offset based on the measuring value to be stored in a memory. Thereafter, correction data stored in the memory is sequentially supplied to a feedback controlling circuit at an actual scan-exposure time. Also, a measuring value of the position of a wafer in a Z-axial direction with the movement of the wafer stage to the scanning direction, relatively moving with the reticle stage, is supplied to the feedback controlling circuit from a wafer position measuring device. The feedback controlling circuit controls a wafer Z-axial driving mechanism such that the position of the wafer in the Z-axial direction is offset by a positional change of the reticle in upper and lower directions. Thereby, correcting a shift of a projection image from a focal position at an exposure surface on the wafer due to deformation (curve and tilt) of the reticle and the upper and lower movement.