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Fast source optimization involving quadratic line-contour objectives for the resist image.
Jue-Chin Yu1, Peichen Yu, Hsueh-Yung Chao
1Department of Photonics and Institute of Electro-Optical Engineering, National Chiao-Tung University, Hsinchu, Taiwan.
Optics Express
|March 29, 2012
Summary
This study introduces novel line-contour objectives for faster source optimization (SO) in lithography. The new method achieves a 100x speedup with similar image quality and an improved process window.
Area of Science:
- Photolithography
- Optical Engineering
- Computational Imaging
Background:
- Source optimization (SO) in lithography typically uses linear or quadratic objective functions.
- Conventional resist imaging involves sigmoid transformation, limiting its use in SO and simultaneous source and mask optimization (SMO).
Purpose of the Study:
- To develop a faster and effective method for source optimization (SO) in photolithography.
- To approximate the resist image effect using quadratic objectives for improved convergence in SO and SMO.
Main Methods:
- Formulated a linear combination of two quadratic line-contour objectives to approximate resist imaging.
- Employed a conjugate gradient method for efficient convergence to the global minimum.
- Compared the proposed line-contour objectives with the conventional sigmoid resist-image model using steepest descent.
Main Results:
- Achieved a 100x speedup in optimization compared to the conventional method.
- Maintained comparable image fidelity between the proposed and conventional approaches.
- Observed a slightly improved process window with the line-contour objectives.
Conclusions:
- The proposed line-contour objectives offer a significant speedup for source optimization (SO) in photolithography.
- This approach provides a viable alternative to traditional resist-image objectives, enhancing computational efficiency.
- The method demonstrates potential for improved lithographic process control and performance.
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