Extreme Ultraviolet Lithography (EUVL) is considered the leading lithography technology choice for semiconductor
devices at 16nm HP node and beyond. However, before EUV Lithography can enter into High Volume Manufacturing
(HVM) of advanced semiconductor devices, the ability to guarantee mask integrity at point-of-exposure must be
established. Highly efficient, damage free mask cleaning plays a critical role during the mask manufacturing cycle and
throughout the life of the mask, where the absence of a pellicle to protect the EUV mask increases the risk of
contamination during storage, handling and use. In this paper, we will present effective EUVL mask cleaning
technology solutions for mask manufacturing and in-fab mask maintenance, which employs an intelligent, holistic
approach to maximize Mean Time Between Cleans (MBTC) and extend the useful life span of the reticle. The data
presented will demonstrate the protection of the capping and absorber layers, preservation of pattern integrity as well as
optical and mechanical properties to avoid unpredictable CD-linewidth and overlay shifts.
Experiments were performed on EUV blanks and pattern masks using various process conditions. Conditions showing
high particle removal efficiency (PRE) and minimum surface layer impact were then selected for durability studies.
Surface layer impact was evaluated over multiple cleaning cycles by means of UV reflectivity metrology XPS analysis
and wafer prints. Experimental results were compared to computational models. Mask life time predictions where made
using the same computational models.
The paper will provide a generic overview of the cleaning sequence which yielded best results, but will also provide
recommendations for an efficient in-fab mask maintenance scheme, addressing handling, storage, cleaning and