A novel concept for actinic EUV mask review tool using a scanning lensless imaging method at the Swiss Light Source (Withdrawal Notice)

Abstract

EUV mask defect inspection and review infrastructure is still one of the main challenges of extreme ultraviolet lithography (EUVL), and mask metrology requirements continue to evolve for successful EUVL readiness. It is well recognized that one of the key infrastructure for EUV masks is the development of an actinic mask review tool that can emulate the properties of EUV scanner for high-volume manufacturing. We demonstrate an actinic EUV mask review tool using a scanning variant of coherent diffraction imaging (CDI) method, called ptychography. Ptychography is a lensless imaging technique and as a hybrid of scanning transmission microscopy and CDI, it combines many of the benefits offered by both techniques. Ptychography provides both amplitude and phase information of the specimen with high resolution, relaxed depth of focus, and high throughput. To apply this technique in reflection and EUV wavelength for actinic mask imaging we developed a 'Reflective EUV Mask Scanning Lensless Imaging' (RESCAN) prototype. We show the first imaging performance of this tool through reconstructed images of test patterns on a multilayer mask. We show the current status of actinic RESCAN using 0.1 (0.4/4) NA and 6° of angle of incidence off-axis illumination and its potential of mask inspection with a proof-of-principle reconstruction of a test pattern. © 2014 SPIE.