In this paper, we present a method for accurate EUV mask inspection of arbitrarily shaped absorber patterns using lensless imaging methods. With our reflective-mode EUV mask scanning lensless imaging microscope (RESCAN), we have imaged a mask with programmed defects and present here the computed defect map for both die-to-die and die-to-database pattern inspection. The signal-to-noise ratio in both cases was high enough to clearly isolate the defect from the structures (~13 for die-to-die and ~7 for die-to-database inspection).
To reach the high-throughput required by industry, we implemented an extended ptychographic algorithm that allows for continuous scanning of the sample and subsequent deconvolution of the distortions in the incident illumination that are due to the fast stage movement. We will show how this algorithm was implemented on a multi-GPU platform for maximum performance that will eventually allow us to reach the final goal of 7 hours scan time for a full mask.
Patrick Helfenstein, Iacopo Mochi, Rajendran Rajeev, Sara Fernandez, Dimitrios Kazazis, and Yasin Ekinci, "High-throughput defect inspection for arbitrarily shaped EUV absorber patterns (Conference Presentation)," Proc. SPIE 10585, Metrology, Inspection, and Process Control for Microlithography XXXII, 1058509 (Presented at SPIE Advanced Lithography: February 27, 2018; Published: 19 March 2018); https://doi.org/10.1117/12.2297587.5754457171001.
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