TW429413B - Projection exposure device, projection exposure method, optical cleaning method, and the method of fabricating semiconductor device - Google Patents

Abstract

A photosensitive wafer is exposed to light of a target illuminance regardless of the variation of time-varying transmittance of an optical system, and the exposure process is proceeded as follows. There are 20,000 pulses idly shot before starting exposure of a first wafer (25). When the first and 20,000th laser pulses produce oscillations, the transmittances of the optical system are calculated at the two moments by acquiring the output signals from an integrator sensor (10) and an illuminance sensor (28), and then a predictive line of time-varying transmittance is calculated from the two transmittances. When the exposure is started, the transmittance of the optical system is calculated at the elapsed time of exposure from the predictive line of time-varying transmittance, and the intensity of exposing light is controlled. Therefore, the illuminance on the wafer can be adjusted depending on the actual variation of the transmittance. Also, the accumulated quantity of exposing light incident to the wafer (25) is regulated to ensure a target exposure dose of the wafer (25), so that the accumulated quantity of exposing light incident to the wafer can reach a target value regardless of the variation in the transmittance of an illumination optical system or a projection optical system during exposure.