Method of projection exposure and stepper

Abstract

A stepper is provided with an optical illumination system and an optical projection system having variable stops, respectively. Such a stepper is capable of preventing the harmful effects which are produced by the operation to be executed in a state where the direct rays passing the variable stop on the optical illumination system side irradiate the variable stop on the optical projection system side when the aperture numbers are set by the variable stops, respectively. For the stepper which is provided with an illuminating system to illuminate a reticle, an optical projection system to image the projected image of the reticle on a transferring substrate, a first variable stop device to make variable the aperture number of an irradiation light converging optical system for the reticle, which is arranged in the illumination system, and a second variable stop device to make variable the aperture number of the optical system arranged in the optical projection system, there is provided a control device to cause the exposure operation to be disabled except when the aperture numbers each set by the first and second variable stop devices allow all of the zero order diffraction rays passing the first variable stop device to pass the aperture of the second variable stop device.