Patent ID: 7443484

Claim:
A method for exposing a semiconductor wafer with a pattern from a reticle in an exposure tool, the exposure tool comprising a reticle stage, a projection lens system and a wafer stage, with the reticle and wafer stages and the lens system being arranged along an optical axis, the method comprising: providing the semiconductor wafer to the wafer stage and the reticle to the reticle stage of the exposure tool; applying a periodic movement having a frequency to the semiconductor wafer along the optical axis such that a position of the semiconductor wafer with respect to a focal plane of the projection lens system is periodically varied; moving a plurality of optical elements of the projection lens system coincidentally and periodically with the frequency of the periodic movement of the semiconductor wafer, wherein the plurality of optical elements are also moved independently of each other in combination with being moved periodically to facilitate a determination of a superposition of induced aberrations in the projection lens system, and the plurality of optical elements are further moved coincidently with respect to each other to facilitate a shift in the focal plane to a desired position; and directing a light beam from an illumination source of the exposure tool to the reticle and further directing the light beam from the reticle through the projection lens system onto a portion of a surface of the semiconductor wafer while the periodic movement is applied to the wafer and while periodic and independent movement is applied to the optical elements.