JPS6431417A - Reduction projection aligner - Google Patents

Abstract

PURPOSE:To inspect automatically dust accumulated on upper and lower surfaces of an exposure mask, by irradiating the lower surface of the exposure mask with exposure rays and by detecting scattered light from the dust by using a CCD camera. CONSTITUTION:A lower surface irradiating device 3 may insert a lens 3e located at the point of a whirling arm 3b between an exposure mask 2 and a reduced projection exposure lens 8 by rotating a rotation axis 3a. If there is dust 6u attached to an upper surface U of the exposure mask 2, scattered lights 5a are detected as images of a CCD camera 4. That is to say, as dust is detected on image plane scanning lines as luminant signals, control signals are automatically outputted to an alarm display or an air blower for blowing away dust when signals exceeding the prescribed level are detected. When dust 6 which is attached to a lower surface L of the exposure mask 2 is detected, lights emitted from a different light source are applied from the lens 3e to the lower surface L of the exposure mask 2 through a mirror 3c of the rotation axis 3a and the mirror 3d located at the point of the whirling arm 3b. If there is dust 6b, the scattered lights 7b are detected as the images of the CCD camera 4.