2 February 2009 Focusing and leveling system for optical lithography using linear CCD
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Abstract
This paper proposes a focusing and leveling technique for optical lithography tools using linear CCD and image processing method. A double telecentric optical system is designed, which projects an aperture onto the surface of the wafer at a large incident angle, and then the reflected beam results in a spot image onto a linear CCD. A mathematical model relating the spot lateral displacement to the change of wafer height is established. Two image processing algorithms for displacement detection of the spot image measured by the linear CCD are also proposed. A lot of experiments including the system calibration conducted on a test rig confirm that the proposed technique is feasible and effective. The repetitive height measurement accuracy of the system is verified to be more than 200 nm within a wide band measurement range of 1 mm.
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Tao Huang, Shiyuan Liu, Pengxing Yi, Tielin Shi, "Focusing and leveling system for optical lithography using linear CCD", Proc. SPIE 7160, 2008 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Applications, 71602X (2 February 2009); doi: 10.1117/12.808083; https://doi.org/10.1117/12.808083
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