Wave-front reconstruction with Hartmann-Shack sensor using a phase-retrieval method

We apply a phase retrieval algorithm to the intensity patterns acquired from a Hartmann-Shack wave-front sensor to measure the wave-front aberration of a deep ultraviolet lithography system. The intensity patterns are obtained with and without the micro-lens array. Thus, we avoid selecting algorithm-specific parameters such as step-size and trust-region. Simulation results show that the phase-retrieval method enhances the accuracy of wave-front reconstruction compared with the conventional wave-front slope method. The relationships between the number of iterations of the phase retrieval algorithm, the calculating time and the wave-front reconstruction error are studied. This study demonstrates that the phase-retrieval method provides more accurate estimates of aberrations in near-flat wave-fronts relative to the wave-front slope method.