Paper
8 July 2022 Heterodyne three-degree-of-freedom grating interferometer for ultra-precision positioning of lithography machine
Junhao Zhu, Guochao Wang, Gaopeng Xue, Qian Zhou, Xinghui Li
Author Affiliations +
Abstract
In this paper, we proposed a new reflection type heterodyne three-degree-of-freedom (three-DOF) grating interferometer for ultra-precision positioning of the worktable of the lithography machine. The grating interferometer is based on a 780 nm wavelength dual-frequency laser that can generate a 40 kHz beat signal through two acoustic-optical modulators (AOM). The reflected lights from the grating and the mirror are used to obtain the heterodyne interference signal in the z-direction, and the four beams of diffracted light from the two-dimensional planar grating are used to obtain the heterodyne interference signal in the x- and y-directions. By comparing the phase of the reference signal, the phase changes in the x-, y-, and z- directions are calculated to derive the three-DOF displacement. Based on optical subdivision and electronic subdivision, the analysis result shows that the resolutions in the x- and y-directions are 0.069 nm, and in the z-direction is 0.108 nm, providing a nanometer resolution for all three axes. In the experiment, the z-direction measurement optical path was constructed to test the static stability of the zero-crossing point of the heterodyne interference signal and the straightness of the z-direction displacement. The preliminary experiment result verified that this interferometer can simultaneously provide the static stability of the zero-crossing point of ±0.1 nm and high straightness. Due to the common optical path design of x-, y- and z-directions, the heterodyne three-DOF grating interferometer structure can be compact and allow a high-performance uniformity of the three axes.
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Junhao Zhu, Guochao Wang, Gaopeng Xue, Qian Zhou, and Xinghui Li "Heterodyne three-degree-of-freedom grating interferometer for ultra-precision positioning of lithography machine", Proc. SPIE 12282, 2021 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Systems, 1228204 (8 July 2022); https://doi.org/10.1117/12.2616683
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KEYWORDS
Interferometers

Heterodyning

Lithography

Laser systems engineering

Optical testing

Mirrors

Polarization

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