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A real-time exposure dose control algorithm for
DUV excimer lasers |
| Liu Shiyuan, Wu Xiaojian, Qin Xinyi |
| State Key Laboratory of Digital Manufacturing Equipment and Technology, Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology |
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Abstract A real-time exposure dose control algorithm for deep ultraviolet (DUV) excimer lasers in a step-and-scan optical lithography is presented. By establishing an abstract scan exposure model and analyzing the pulse-to-pulse energy fluctuation characteristics of DUV excimer lasers, a real-time dose regulation is implemented based on closed-loop feedback control, which especially focuses on reducing the effect of pulse energy overshot and pulse-to-pulse stochastic fluctuation. The experiment conducted on an ArF excimer laser with wavelength of 193 nm, repetition rate of 4 kHz, and pulse energy of 5 mJ confirms that such a real-time dose control algorithm is able to achieve a dose accuracy of above 0.89% even with only 20 pulses. It is fully expected that this algorithm will not only meet increasingly stringent dose accuracy requirements for sub-half-micron lithography, but also be helpful to improve lithography throughput as well as efficiency.
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Issue Date: 05 June 2008
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