Scanning scattering contrast microscopy for actinic EUV mask inspection

I. Mohacsi; P. Helfenstein; R. Rajendran; Y. Ekinci

doi:10.1117/12.2220027

24 March 2016 Scanning scattering contrast microscopy for actinic EUV mask inspection

I. Mohacsi, P. Helfenstein, R. Rajendran, Y. Ekinci

Proceedings Volume 9778, Metrology, Inspection, and Process Control for Microlithography XXX; 97781O (2016) https://doi.org/10.1117/12.2220027
Event: SPIE Advanced Lithography, 2016, San Jose, California, United States

Abstract

Actinic mask inspection for EUV lithography with targeted specification of sensitivity and throughput is a big challenge and effective solutions are needed. We present a novel method for actinic mask inspection, i.e. scanning scattering contrast microscopy. In this method the EUV mask is scanned with a beam of relatively small spot size and the scattered light is recorded with a pixel detector. Since the mask layout is known, the scattering profile of a defect-free mask at the detector can be calculated. The signal between the measured and calculated signal provides the deviation between the real mask and its ideal counterpart and a signal above a certain threshold indicates the existence of a defect within the illumination area. Dynamic software filtering helps to suppress strong diffraction from defect free structures and allows registration of faint defects with high sensitivity. With the continuous scan of the whole mask area, a defect map can be obtained with high throughput. Therefore, we believe that this method has the potential of providing an effective solution for actinic mask inspection. Here we discuss the basic principles of the method, present proof-of-principle experiments, describe the basic components of a feasible stand-alone tool and present early results of the performance estimations of such a tool.

Citation Download Citation

I. Mohacsi, P. Helfenstein, R. Rajendran, and Y. Ekinci "Scanning scattering contrast microscopy for actinic EUV mask inspection", Proc. SPIE 9778, Metrology, Inspection, and Process Control for Microlithography XXX, 97781O (24 March 2016); https://doi.org/10.1117/12.2220027

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