Projection Exposure System, Beam Delivery System and Method of Generating a Beam of Light

摘要

A beam delivery system of a projection exposure system comprises a laser generating a beam of laser light from a plurality of longitudinal laser modes in a cavity, wherein light generated by a single longitudinal laser mode has an average line width lambda_lat, wherein the laser light of the beam has, at each of respective lateral positions of the beam, a second line width lambda_lat corresponding to lateral laser modes, and wherein the laser light of the beam has, when averaged over a whole cross section thereof, a line width lambda_b corresponding to plural lateral laser modes, and wherein lambda_mlatb, and wherein an optical delay apparatus disposed in the beam provides an optical path difference Deltal, wherein $0.8.\frac{{\mathrm{lambda}}_0^2}{\left(2.\mathrm{Delta}{\mathrm{lambda}}_l\right)}<\mathrm{Delta}l<1.8.\frac{{\mathrm{lambda}}_0^2}{\left(2.\mathrm{Delta}{\mathrm{lambda}}_l\right)},$ wherein lambda₀ is an average wavelength of the light of the first beam of laser light, and Deltalambda_lat represents the second line width.