Actinic review of EUV masks: performance data and status of the AIMS EUV system

The EUV mask infrastructure is of key importance for the successful introduction of EUV lithography into volume production. In particular, for the production of defect free masks an actinic review of potential defect sites is required. ZEISS and the SUNY POLY SEMATECH EUVL Mask Infrastructure consortium have developed such an EUV aerial image metrology system, the AIMS™ EUV, with the prototype tool regularly being used for customer measurement campaigns and the first system shipped to customer end of last year. In this paper, we provide an update on the system performance and present quantitative measurements of the impact of mask surface roughness on the aerial image. We show that an increasing amount of effects is only visible in actinic aerial imaging and discuss potential benefits of aerial image based mask qualification.