MESA+ University of Twente
Industrial focus group XUV Optics




Project Type

Granted HTSM 2013 project



Project Leader

Dr. C. Lee



Cost estimate

M€ 0.57

Base funding

High Tech Systems and Materials programme, ASML, Carl Zeiss SMT AG



Current and future photolithography processes operate in the extreme ultraviolet (EUV), which requires reflecting optics. The operating conditions of an EUV lithography tool present a reactive environment that can react with the component materials of the EUV optics, ultimately destroying them. Also particulate contaminants are created in the EUV environment, which adhere to the mask in a wafer scanner and are imaged sharply on the wafer. To prevent these effects, protective capping layers are placed on the EUV optics and a protective pellicle is placed in front of the mask, out of the depth of focus of the imaging system. Both the pellicle and the capping layers need to be chemically inert under EUV irradiation, and EUV transparent. In addition, the pellicle needs to be mechanically strong and the capping layer needs to be impermeable to maintain the reflectivity of EUV optics. At present, there are only few EUV compatible pellicle solutions that are commercially acceptable. In addition, current capping layers need further improvement before commercialization.

In this proposal, the effect of EUV irradiation under EUV lithography operating conditions on novel materials such as graphene and ultra-thin membranes deposited by atomic layer deposition (ALD) are explored. Both graphene and ALD membranes are extremely thin (~nm), and therefore will exhibit exceptional EUV optical properties. In addition, graphene is mechanically very strong and chemically inert. Therefore these materials are promising candidates for pellicle materials and protective coatings on EUV optics.