Actinic patterned mask inspection for EUV lithography

Abstract

EUV lithography enters the high-volume manufacturing stage, and the semiconductor industry considers a lithography-wavelength- matched actinic patterned mask inspection (APMI) tool to be a crucial infrastructure for EUV mask qualification. ACTIS^TM, the world’s first high-sensitivity actinic patterned mask inspection system, was released in 2019. ACTIS detects lithographic impact defects that cannot be seen with the existing DUV inspection tools. The actual results of production mask inspection show that only an actinic EUV inspection system can visualize small surface topography and phase changes that propagate through multilayer stacks. In this paper, we present the progress of ACTIS inspection technology, defect sensitivity, die-to-database inspection and through pellicle inspection. For technology nodes beyond N3, a high-NA EUV anamorphic lithography system will be used. The mask structure in the high-NA era will be different from the current configuration. For inspection tool design, it is necessary to adopt a different magnification of mask-to-wafer projection in the vertical and horizontal directions. ACTIS has the extendibility to a high-NA system since its projection NA area has room for extension in one direction. The high-NA EUV inspection tool will be discussed in this paper as well.