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Real-time control of ion density and ion energy in chlorine inductively coupled plasma etch processing

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6 Author(s)
Chang, Cheng-Hung ; Department of Engineering and System Science, National Tsing Hua University, Hsinchu, Taiwan 30043, Republic of China ; Leou, Keh-Chyang ; Lin, Chaung ; Lin, Tsan-Lang
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In this study, we have experimentally demonstrated the real-time closed-loop control of both ion density and ion energy in a chlorine inductively coupled plasma etcher. To measure positive ion density, the trace rare gases-optical emission spectroscopy is used to measure the chlorine positive ion density. An rf voltage probe is adopted to measure the root-mean-square rf voltage on the electrostatic chuck which is linearly dependent on sheath voltage. One actuator is a 13.56 MHz rf generator to drive the inductive coil seated on a ceramic window. The second actuator is also a 13.56 MHz rf generator to power the electrostatic chuck. The closed-loop controller is designed to compensate for process drift, process disturbance, and pilot wafer effect and to minimize steady-state error of plasma parameters. This controller has been used to control the etch process of unpatterned polysilicon. The experimental results showed that the closed-loop control had a better repeatability of plasma parameters compared with open-loop control. The closed-loop control can eliminate the process disturbance resulting from reflected power. In addition, experimental results also demonstrated that closed-loop control has a better reproducibility in etch rate as compared with open-loop control. © 2003 American Vacuum Society.

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Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films  (Volume:21 ,  Issue: 4 )