20 April 2011 Real-time detection system of defects on a photo mask by using the light scattering and interference method
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It was reported that the ArF excimer laser mainly used in the process of lithography for semiconductor devices cause pollutants on a photo-mask by various photochemical reactions, which is called by the haze. Therefore, the real time detection system on the lithography process is needed in order to inspect the generation of defects containing the haze on the mass production system before and/or after the generation of defects. We proposed and experimentally confirmed the concept of the new real time detection system to detect automatically and visually many defects with several hundred nanometer size generating on a photo-mask by using interference fringes generated by interfering between the light wave scattered by small defects of a photo-mask and the reflected light wave from the rest area of the front surface. In order to balance the contrast ration of two interference light waves, we utilized the incident beam with the nearly Brewster angle on the photo-mask and a linear polarizer aligned in front of the CCD camera. For all of the Cr defects from the size of 0.6 μm to that of 10 μm we succeeded to detect the interference fringes between the scattered beam and the reference beam.
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Jae Heung Jo, Jae Heung Jo, Sangon Lee, Sangon Lee, Hae Sung Wee, Hae Sung Wee, Jong Soo Kim, Jong Soo Kim, } "Real-time detection system of defects on a photo mask by using the light scattering and interference method", Proc. SPIE 7971, Metrology, Inspection, and Process Control for Microlithography XXV, 79711R (20 April 2011); doi: 10.1117/12.881685; https://doi.org/10.1117/12.881685

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