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20 August 2004 High-speed actinic EUV mask blank inspection with dark-field imaging
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Proceedings Volume 5446, Photomask and Next-Generation Lithography Mask Technology XI; (2004) https://doi.org/10.1117/12.557814
Event: Photomask and Next Generation Lithography Mask Technology XI, 2004, Yokohama, Japan
Abstract
We proposed an actinic (at-wavelength) EUV mask blank inspection method providing a printable phase-defect detection capability within the whole area of the mask blanks in an allowable inspection time. The inspection tool based on our method consists of optics for illuminating a mask blank with an EUV light, a mask blank stage, Schwarzschild optics for dark-field imaging, and a CCD camera. Phase-defect detection experiments were performed using a 10 Hz LPP source and with 0.2 NA imaging optics with the center obscuration NA of 0.1. Two-dimensional dark field image signal of 0.5 mmX0.5 mm area was captured by the CCD camera with 1M pixels and the phase-defects with the size down to 70 nm were successfully detected. In addition, a programmed phase defect and natural defect with 2 nm height were clearly detected. Inspection time including image capture and data processing for 0.5 mmX0.5 mm area was approximately 2 second. This is equivalent to an inspection time of 800 seconds/cm2. Inspection speed will increase by more than 10 times when combined with high power light source and high speed data acquisition. Although further optimization is needed, possibility of actinic inspection of EUV mask blanks within a practical inspection time has been demonstrated.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Tsuneo Terasawa, Yoshihiro Tezuka, Masaaki Ito, and Toshihisa Tomie "High-speed actinic EUV mask blank inspection with dark-field imaging", Proc. SPIE 5446, Photomask and Next-Generation Lithography Mask Technology XI, (20 August 2004); https://doi.org/10.1117/12.557814
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