Full optical column characterization of DUV lithographic projection tools

Advanced optical systems for low k₁ lithography require accurate characterisation of various imaging parameters to insure that OPC strategies can be maintained. Among these parameters lens aberrations and illumination profiles are the most important optical column charcteristics. The phase measurement interferometer hardware (ILIAS: Integrated Lens Interferometer At Scanner) integrated into high-NA ArF lithographic projection tools opens novel pathways to measure and control tool critical performance parameters. In this presentation we address new extensions of this in-line tool that will allow the measurement of optical parameters of the full optical column. The primary functionality of the ILIAS system is to measure and analyse wavefront aberrations across the full image field with high accuracy and speed. In this paper performance data of the in-line wavefront sensor over multiple high-NA ArF lithographic systems is presented. In addition to the acquisition of wavefront aberrations in terms of Zernike polynomials, detailed measurements of high resolution wavefronts are now possible. Examples of such wavefronts and PSD analysis thereof are presented. Besides the projection lens properties, the detailed shape of the pupil distribution and transmission (apodisation) becomes critical for system optimization. The integrated ILIAS hardware can also be used to measure these parameters.