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Fringe Pattern Analysis for Optical Alignment in Nanolithography Using Two-dimentional Fourier Transform
Author(s): Xu, F (Xu, Feng); Song, H (Song, Hu); Zhou, SL (Zhou, Shaolin)
Source: OPTICAL ENGINEERING Volume: 50 Issue: 8 Article Number: 088001 DOI: 10.1117/1.3609007 Published: AUG 2011
Abstract: A simple but effective phase analysis method for the fringe pattern that occurs in two superposed grating marks applied in the previously designed dual-grating-based alignment scheme for lithography is proposed. First, the fringe pattern is processed and analyzed using a frequency domain method based on two-dimensional (2D) Fourier transform, and the 2D notch filter is appropriately designed to select the useful spectrum to obtain the target phase information. Further, phase difference of two sets of fringes is computed to acquire the alignment offset. Numerical simulation and experiment are both performed to verify this method. Finally, certain analysis about the error of phase difference extraction in the fringe pattern and precision of alignment are also presented. The results indicate that the background and noise of the fringe pattern can be efficiently filtered and target phase information can be extracted with high accuracy through this method. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3609007]
Addresses: [Xu, F] Chinese Acad Sci, Inst Opt & Elect, Chengdu 610209, Peoples R China
Chinese Acad Sci, Grad Univ, Beijing 100039, Peoples R China
Reprint Address: Xu, F (reprint author), Chinese Acad Sci, Inst Opt & Elect, Chengdu 610209, Peoples R China
E-mail Address: casxufeng@gmail.com
IDS Number: 812PX
Source: OPTICAL ENGINEERING Volume: 50 Issue: 8 Article Number: 088001 DOI: 10.1117/1.3609007 Published: AUG 2011
Abstract: A simple but effective phase analysis method for the fringe pattern that occurs in two superposed grating marks applied in the previously designed dual-grating-based alignment scheme for lithography is proposed. First, the fringe pattern is processed and analyzed using a frequency domain method based on two-dimensional (2D) Fourier transform, and the 2D notch filter is appropriately designed to select the useful spectrum to obtain the target phase information. Further, phase difference of two sets of fringes is computed to acquire the alignment offset. Numerical simulation and experiment are both performed to verify this method. Finally, certain analysis about the error of phase difference extraction in the fringe pattern and precision of alignment are also presented. The results indicate that the background and noise of the fringe pattern can be efficiently filtered and target phase information can be extracted with high accuracy through this method. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3609007]
Addresses: [Xu, F] Chinese Acad Sci, Inst Opt & Elect, Chengdu 610209, Peoples R China
Chinese Acad Sci, Grad Univ, Beijing 100039, Peoples R China
Reprint Address: Xu, F (reprint author), Chinese Acad Sci, Inst Opt & Elect, Chengdu 610209, Peoples R China
E-mail Address: casxufeng@gmail.com
IDS Number: 812PX
