Phase demodulation method for fringe pattern in alignment of nanometer lithography

Feng Xu; Song Hu; Zhengquan Luo

doi:10.1117/12.866811

22 October 2010 Phase demodulation method for fringe pattern in alignment of nanometer lithography

Feng Xu, Song Hu, Zhengquan Luo

Proceedings Volume 7657, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems; 76571B (2010) https://doi.org/10.1117/12.866811
Event: 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies, 2010, Dalian, China

Abstract

The relative position of mask and wafer can be reflected by the variation of the spatial phase in the alignment method basing on spatial phase of fringe pattern, through spatial phase imaging of grating modulation. The relative displacement of mask and wafer can be obtained from spatial phase demodulation of fringe patterns to carry out the alignment process. Generally, the windowed Fourier transform (WFT) is representative method for spatial phase demodulation of the fringe pattern. It is robust and accurate, but it is computational redundant for the alignment of nanolithography. This paper presents a phase demodulation method which has good accuracy and can be carried out in real time to meet the need of the alignment of nanolithography. This method is improved on the basis of the traditional WFT. The fast Fourier transform (FFT) is introduced to WFT and the phase is computed by integrating the phase gradient which is extracted directly from the fringe pattern through generation of the adaptive windowed Fourier elements. These two improvements can individually reduce the computation time for spatial phase demodulation of fringe pattern. The theoretical background and the principle of the algorithm of fringe pattern analysis are proposed. Numeric computation indicate that this method is of high accuracy and computational efficient for fringe pattern analysis, which show high significance for application of alignment of nanolithography.

Citation Download Citation

Feng Xu, Song Hu, and Zhengquan Luo "Phase demodulation method for fringe pattern in alignment of nanometer lithography", Proc. SPIE 7657, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems, 76571B (22 October 2010); https://doi.org/10.1117/12.866811

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KEYWORDS

Fringe analysis

Fourier transforms

Demodulation

Optical alignment

Phase shift keying

Nanolithography

Lithography

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