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Proceedings Paper

Design of the ultraprecision stage for lithography using VCM
Author(s): Jung-Han Kim; Mun-Su Kim; Min-Taek Oh
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Paper Abstract

This paper presents a new design of precision stage for the reticle in lithography process and a low hunting control method for the stage. The stage has three axes for X,Y, θZ, those actuated by three voice coil motors individually. The proposed precision stage system has three gap sensors and voice coil motors, and supported by four air bearings, so it do not have any mechanical contact and nonlinear effect such as hysterisis which usually degrade performance in nano level movement. The reticle stage has cross coupled dynamics between X,Y,θZ, axes, so the forward and inverse kinematics were solved to get an accurate reference position. When the stage is in regulating control mode, there always exist small fluctuations (stage hunting) in the stage movement. Because the low stage hunting characteristic is very important in recent lithography and nano-level applications, the proposed stage has a special regulating controller composed of digital filter, adjustor and switching algorithm. Another importance factor that generates hunting noise is the system noise inside the lithography machine such as EMI from another motor and solenoids. For reducing such system noises, the proposed controller has a two-port transmission system that transfers torque command signal from the DSP board to the amplifier. The low hunting control algorithm and two-port transmission system reduced hunting noise as 35nm(rms) when a conventional PID generates 77nm(rms) in the same mechanical system. The experimental results showed that the reticle system has 100nm linear accuracy and 1μ rad rotation accuracy at the control frequency of 8 kHz.

Paper Details

Date Published: 9 January 2008
PDF: 6 pages
Proc. SPIE 6794, ICMIT 2007: Mechatronics, MEMS, and Smart Materials, 67941P (9 January 2008); doi: 10.1117/12.784429
Show Author Affiliations
Jung-Han Kim, Seoul National Univ. of Technology (South Korea)
Mun-Su Kim, Seoul National Univ. of Technology (South Korea)
Min-Taek Oh, Seoul National Univ. of Technology (South Korea)

Published in SPIE Proceedings Vol. 6794:
ICMIT 2007: Mechatronics, MEMS, and Smart Materials
Minoru Sasaki; Gisang Choi Sang; Zushu Li; Ryojun Ikeura; Hyungki Kim; Fangzheng Xue, Editor(s)

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