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Proceedings Paper

Lithographic tool dynamic coordinate calibration for CDU improvement
Author(s): Zhiyong Yang; Fanglin Mao; Anatoly Bourov; Jianrui Cheng; Le He
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Paper Abstract

In lithographic scanner, many different physical factors could impact to image quality and CD uniformity. In optical systems, the pupil filling quality (source shape), wavefront error and stray light can decrease the intensity contrast and shrink the process window. In mechanical domain, the vibration and scanning synchronization error have the similar effect to imaging process. Imaging in scanner is a dynamic exposure process and in this process, aerial image should keep the same relative position to the wafer. It requests the lithographic tool must have a very stable mechanical frame and very good motion control performance. In addition, the wafer stage, reticle stage's coordinate and projection lens' grid should be matched exactly, include the scanning direction and velocity ratio. The tool's alignment system can calibrate the statistic coordinate for overlay, but it cannot calibrate the dynamic coordinate in scanning direction very well because projection lens' grid has a small asymmetric signiture. This systematic error should be calibrated for CDU improvement. An imaging model considering the motion blurring is represented in this paper and based on this model, the dynamic coordinate's error could be analyzed. Furthermore, exposure method can be used to calibrate the dynamic coordinate and improve the CD uniformity. Exposure latitude will be used to check and calibrate the lithographic tool's dynamic coordinate. We designed a special calibration process to obtain the best dynamic coordinate setting for scanner. In this process, some tool's coordinate parameters (scanning skew and scale) have been changed for every field to obtain the multi-dimensions' exposure information. Exposure window can be represented from this result, and in this exposure window, the best dynamic coordinate setting could be found. After the dynamic coordinate calibrated, the CDU is improved.

Paper Details

Date Published: 13 March 2012
PDF: 9 pages
Proc. SPIE 8326, Optical Microlithography XXV, 83262G (13 March 2012); doi: 10.1117/12.915975
Show Author Affiliations
Zhiyong Yang, Shanghai Micro Electronics Equipment Co., Ltd. (China)
Fanglin Mao, Shanghai Micro Electronics Equipment Co., Ltd. (China)
Anatoly Bourov, Shanghai Micro Electronics Equipment Co., Ltd. (China)
Jianrui Cheng, Shanghai Micro Electronics Equipment Co., Ltd. (China)
Le He, Shanghai Micro Electronics Equipment Co., Ltd. (China)

Published in SPIE Proceedings Vol. 8326:
Optical Microlithography XXV
Will Conley, Editor(s)

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