Method for projection exposure to light

Abstract

A method and apparatus for projection exposure applied to photolithography in the field of production of semiconductor devices. An illuminating light which has passed through a silt having an opening width is swept relative to a photomask for projecting a pattern of the photomask on a wafer using a projection optical system. As the illuminating light is swept a distance equal to the opening width of the slit in a direction along the x-axis, the imaging plane is oscillated by one period a distance equal to 2 .mu.m. Specifically, during the time the photomask is moved by the above distance in the direction along the axis x, with the illuminating unit and the projection optical system remaining fixed, the wafer is moved in the x-axis direction in synchronism with the photomask 4 at the same time as the wafer is oscillated by one period with an amplitude 2 .mu.m in the direction along the z-axis. The FLEX method may be applied to the projection exposure of the step-and-scan system such that enlargement of the exposure area and the depth of focus may be achieved simultaneously. Thus, in the process for manufacturing a semiconductor device which is miniaturized in size, the photolithographic process can be improved in reliability.