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Implementation of autofocus in alignment system for layered imprint fabrication

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Abstract

Autofocus method based on the analysis of image content information is investigated to reduce the alignment error resulting from mark positioning uncertainty due to defocus in microstructure layered fabrication process based on multilevel imprint lithography. The applicability of several autofocus functions to the alignment mark images is evaluated concerning their uniformity, sharpness near peak, reliability and measure computation efficiency and the most suitable one based on power spectrum in frequency domain (PSFD) is adopted. To solve the problem of too much computation amount needed in PSFD algorithm, the strategy of interested region detection and effective image reconstruction is proposed and the algorithm efficiency is improved. The test results show that the computation time is reduced from 0.316 s to 0.023 s under the same conditions while the other merits of the function are preserved, which indicates that the modified algorithm can meet the mark image autofocusing requirements in response time, accuracy and robustness. The alignment error due to defocus which is about 0.5 μm indicated by experimental results can be reduced or eliminated by the autofocusing implementation.

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Authors and Affiliations

  1. State Key Lab for Manufacturing Systems Engineering, Xi’an Jiaotong University, Xi’an, 710049, China

    Quandai Wang  (王权岱), Yugang Duan  (段玉岗) & Bingheng Lu  (卢秉恒)

  2. School of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, Guilin, 541004, China

    Jiawei Xiang  (向家伟) & Lianfa Yang  (杨连发)

Authors
  1. Quandai Wang  (王权岱)
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  2. Yugang Duan  (段玉岗)
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  3. Bingheng Lu  (卢秉恒)
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  4. Jiawei Xiang  (向家伟)
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  5. Lianfa Yang  (杨连发)
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Corresponding author

Correspondence to Quandai Wang  (王权岱).

Additional information

Supported by National Natural Science Foundation of China (No.50305026) and Open Foundation of Guangxi Key Lab for Manufacturing Systems and Advanced Manufacturing Technology (No.07109008-025-K).

WANG Quandai, born in 1969, male, Dr, lecturer.

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Wang, Q., Duan, Y., Lu, B. et al. Implementation of autofocus in alignment system for layered imprint fabrication. Trans. Tianjin Univ. 15, 294–299 (2009). https://doi.org/10.1007/s12209-009-0052-z

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  • DOI: https://doi.org/10.1007/s12209-009-0052-z

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