Ronchi shearing interferometry is a promising technique for in situ wavefront aberration measurement of the projection lens in advanced photolithography systems. The integrated ILIAS hardware can also be used to measure these parameters.

Besides the projection lens properties, the detailed shape of the pupil distribution and transmission (apodisation) becomes critical for system optimization. Examples of such wavefronts and PSD analysis thereof are presented. In addition to the acquisition of wavefront aberrations in terms of Zernike polynomials, detailed measurements of high resolution wavefronts are now possible. In this paper performance data of the in-line wavefront sensor over multiple high-NA ArF lithographic systems is presented. 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 presentation we address new extensions of this in-line tool that will allow the measurement of optical parameters of the full optical column. 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. Among these parameters lens aberrations and illumination profiles are the most important optical column charcteristics. Advanced optical systems for low k1 lithography require accurate characterisation of various imaging parameters to insure that OPC strategies can be maintained.

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