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24 September 2010 An analysis of correlation between scanning direction and defect detection at ultra high resolution
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As the design rule of wafer has been shrinking, the patterns on the mask also need to be getting smaller and even smaller for some sub-resolution assist features, which makes mask inspection process need a high resolution (HR) inspection systems. For this HR mask inspection, most mask inspector makers adopt a TDI(Time Delay & Integration) sensor to enhance acquired image quality with the acceptable scan speed, thus, to minimize the inspection cost. However, even TDI sensor may not get a sufficient gray level of pattern image for the most advanced mask patterns. Furthermore, it might generate some false defects depending on the pattern shape and scan direction (in combination with pattern direction). We manufactured two programmed defect masks (PDM); one is a ArF EPSM and another is a EUV mask. By inspecting these masks with perpendicular scan directions, respectively, we evaluated the correlation between scan direction and defect size/shape experimentally. We found that the inspection with the parallel direction to pattern direction can increase the inspectability for the patterns and the defect sensitivity since this helps to enhance signal to noise ratio from the TDI sensor. Our analysis can increase sensitivity of TDI sensor effectively without any additional hardware modification.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Kwon Lim, SungPil Choi, Wonil Cho, Dong Hoon Chung, Chan-Uk Jeon, and HanKu Cho "An analysis of correlation between scanning direction and defect detection at ultra high resolution", Proc. SPIE 7823, Photomask Technology 2010, 782334 (24 September 2010);

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