Actinic EUV-mask metrology: tools, concepts, components

Abstract

There is a strong demand for standalone actinic tools for mask blank and mask metrology. We expect to deliver contributions to key issues for the infrastructure tools such as actinic reflectometer, actinic defect inspection and components like high brightness sources together with our partners.With our EUV-reflectometer EUV-MBR we are ready to fulfill HVM requirements in accurate and sensitive spectral metrology. Migrating from mask blanks to masks is supported with integrated fiducial mark detection and small spot sizes of down to < 0.03 mm². Hence, the EUV-MBR is able to detect minimal variations on mask blank and can support process monitoring for our partners in European EXEPT project.For actinic blank inspection a proof of concept experiment based on an EUV microscope at BASC's EUV-Lamp allows for comparing actinic signatures with AFM scans. Results allow for extrapolation to sub 30 nm sensitivity and fast full blank scan.For LPP sources we demonstrated a new concept utilizing a laser, with parameters optimized for high brightness EUV generation and a new regenerative target concept for high position stability, gain, repetition rate operation and efficiency in the first proof of concept experiment. Up to 350 W/(mm² sr) from < 20 µm source size have been demonstrated.