20 April 2010 EUV mask: detection studies with Aera2
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Abstract
The progress of optical lithography towards EUV wavelength has placed mask defectivity among major EUV program risks. Traditional mask inspection was carried in the DUV domain at 19x nm wavelength, similar to ArF lithography. As EUV mask patterns approach the 20nm half-pitch level, the resolution of DUV systems approaches its practical limits. At this limit, the lesson learned from ArF lithography is that contrast may be improved significantly by utilizing resolution enhancement techniques such as off-axis illumination shapes. Here we present an experimental study of the effects of illumination and polarization on contrast and detection. We measured a EUV patterned mask with programmed defects using Aera2 mask inspection tool at 193nm wavelength, equipped with a high NA objective. We compared the contrasts of the patterns and the defect detection signals obtained by employing 4 different illumination shapes and three polarization states: linear along x, linear along y, circular polarization. We learned that in order to achieve the best results both in terms of contrast and in terms of detection, it is most important to choose a suitable exposure conditions. In addition, a proper choice of the polarization state of the illumination can also result in some improvement.
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T. Verdene, T. Verdene, A. Sagiv, A. Sagiv, U. Malul, U. Malul, T. Alumot, T. Alumot, S. Mangan, S. Mangan, } "EUV mask: detection studies with Aera2", Proc. SPIE 7638, Metrology, Inspection, and Process Control for Microlithography XXIV, 76383T (20 April 2010); doi: 10.1117/12.858638; https://doi.org/10.1117/12.858638
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