Effective EUVL mask cleaning technology solutions for mask manufacturing and in-fab mask maintenance

Abstract

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 inspection.

Impact of electron scattering in extreme ultraviolet reflective multilayer on electron image

“…And type II has a Ta based absorber layer on a 100-nm-thick Ru bulk layer as shown in Fig. 12,17,20,21 The electron trajectories inside and outside these samples were simulated using CHARIOT MONTE CARLO software (Abeam Technologies, Inc.). The detail structure of the Ta based absorber layer was described earlier.…”

Towards defect free EUVL reticles: carbon and particle removal by single dry cleaning proces and pattern repair by HIM

“…Because the reticles do not have a pellicle anymore, as was the modus operandi for visible light lithography, cleanliness is becoming critical for the application of EUVL. Wet cleaning of reticles is also under research and results looks promising [4] . However, a dry cleaning technology for rapid removal of organic contamination might be favorable for in-fab cleaning as this has a relatively short cycle time.…”

Pattern inspection of etched multilayer extreme ultraviolet mask

“…7,8 However, the mask structure should be taken into account when dealing with the mask fabrication processes, such as patterned mask inspection, 9-13 critical dimension measurement (CD metrology), 14,15 mask repair, 16,17 and cleaning. 18 Takai et al reported that the reduction of the ML stack down to 20 pairs effectively avoided the collapse of the lines by the cleaning process. 19 However, patterned mask inspection, CD metrology, and repair of this mask structure continue to pose challenges that need to be addressed.…”