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Proceedings Paper

Research on focusing technique based on dual-phase lock-in amplifier in 193nm lithography system
Author(s): Fei Xie; Xiaoping Tang; Song Hu; Wei Yan
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Paper Abstract

With the integration of large scale integrated circuit devices improved, the requirement on resolution of Lithography has been enhanced day by day. The shortening of wavelength of light source and the augment of numerical aperture of projection objective make the effective depth of focus greatly reduced. The aggrandizement of wafer size and exist of focusing error make it clearly that traditional focusing methods cannot meet the harsh requirements of Nano- Lithography any more. Therefore, we need to develop new focusing technologies further. Aiming at the weak output signal of photodetector in nano-scale real-time focusing technique, this paper puts forward an innovative way in which we can make use of dual-phase lock-in amplifier to detect, amplify, filter and demodulate the signal. After a series of post-processing, we can get the defocusing amount of the wafer to make sure whether it is within the scope of effective depth of focus, for the purpose of assuring the exposure quality. We mainly use Simulink tools in Matlab to simulate the scheme model. From the simulation results we can see that dual-phase lock-in amplifier technique can extract the defocusing signal which we cares about excellently, and it does not rely on phase shifter. Compared with traditional methods, this method can obtain the defocusing signal more accurately. It helps to improve focusing precision significantly and lay a theoretical foundation for practicality in the near future.

Paper Details

Date Published: 22 October 2010
PDF: 8 pages
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, 76571D (22 October 2010); doi: 10.1117/12.866711
Show Author Affiliations
Fei Xie, Institute of Optics and Electronics (China)
Graduate Univ. the of Chinese Academy of Sciences (China)
Xiaoping Tang, Institute of Optics and Electronics (China)
Song Hu, Institute of Optics and Electronics (China)
Wei Yan, Institute of Optics and Electronics (China)


Published in SPIE Proceedings Vol. 7657:
5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems
Tianchun Ye; Sen Han; Masaomi Kameyama; Song Hu, Editor(s)

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