22 October 2010 An optical modulation based focus method for optical projection lithography
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An optical modulation method based focus and level scheme is presented for optical projection lithography. The main parts of the focus system are analyzed respectively. Several kinds of modulation methods are adopted to realize nanometer resolution, including grating modulation, polarization modulation and optic-elastic modulation. The grating modulation is realized by imaging objective grating to the surface of modulation grating and then the modulation light is sent to polarization part. The polarization modulation is based on birefringence which can divide optical signal into two parts and each part represents the position and focus error of silicon wafer. Two or more equipments can implement wafer leveling. By introducing optic-elastic modulation, high signal-to-noise is obtained. Analytical result indicates that focusing resolution at nanometer level can be realized.
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Wangfu Chen, Song Hu, "An optical modulation based focus method for optical projection lithography", Proc. SPIE 7657, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems, 76571J (22 October 2010); doi: 10.1117/12.866813; https://doi.org/10.1117/12.866813


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