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Laser has the advantages of single wavelength, directivity, and high instance power, and the laser beam can be focused by optical system to get beam size as close to the Rayliegh diffraction limit. In addition, with the tuning of laser operating parameters, it is able to achieve variable material processing, such as laser drilling, laser cutting, laser printing of semiconductor packaging processes. With the improvement of IC process technology, the number of I/ O is also relatively increasing that makes the layout line width of the substrate shrink, and the defects of photo-lithography such as residue of the photo-resist and short circuit. This thesis is mainly focused on the study of using a Nd: YAG double frequency solid-state laser with wavelength of 532 nm, power of 2 mJ, pulse width of 5 ns, and repeating rate of 1 Hz to remove a photoresist materials of 6 thickness. In the experiment, a surface profiler is used to measure the depth of the photoresist, and parameters of the optical system such as size of the aperture, the angle of the polarizer and the focus position were used to characterize the removal of the photoresist. The result shows that threshold of the photoresist can be achieve with the optical system of 25% aperture, and 90 polarization, and complete removal of the photoresist can be achieve with 65% aperture. However, a smooth and clear profile of photoresist can be reach with small aperture size. The removal rate of the photoresist can be effectively tuned by continuously adjusting the polarizer angle. In the future, this system can be integrated with the wafer optical inspection system to effectively trimming the photoresist and improve the yield of the process.
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