Köhler illumination analysis for high-resolution optical metrology using 193 nm light

Dependence of Köhler factor 2 (KF 2: angular homogeneity) and Köhler factor 3 (KF 3: wavefront homogeneity) on the intensity profile of line target was investigated for an optical system designed for high-resolution optical metrology using ArF excimer laser of a wavelength of 193 nm. The intensity profiles for the isolated and multiple lines of 60 nm linewidth were simulated based on the diffraction propagation by introducing the changes of NA (KF 2) and aberrations such as defocus and coma (KF 3) to the illumination beam. From the results it was demonstrated that the intensity profiles for the line targets were influenced by the change of the illumination condition, being distorted in shape and magnitude.