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Proceedings Paper

EUV repair process optimization and integration
Author(s): Pavel Nesládek; Alexander Lajn; Thorsten Schedel; Markus Bender
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Paper Abstract

EUV technology is according to current trend approaching the final development phase in which defect free EUV masks are of key importance for development and optimization of the lithography process. This task consists of three contributing aspects- defect free multilayer blank, mask manufacturing process with very low defect formation probability and availability of repair process for EUV mask. In comparison to optical mask, development of the repair process for EUV mask is different in several aspects. The fact, that the TaN absorber is placed on top of Mo/Si mirror is making the process very sensitive to variation of the mask material, as the etch rate of the mirror is significantly higher, than that of absorber, when no capping layer is present between the absorber and ML mirror. The presence of the Ru capping layer increases the process window due to significant selectivity improvement by one or two orders of magnitude, however, the capping layer is very sensitive to damage by preceding manufacturing processes. Its thickness and also it chemical purity - lack of modification by incorporation of impurities is crucial for successful mask repair. The repair process for optical masks is typically optimized using AIMS for both development and qualification of the process. The availability of EUV AIMS system is very limited, for what reason we have to rely on other measures during the process development and use the AIMS for process qualification only, or use correlation between e.g. CD SEM or AFM measurement and AIMS data for selection and qualification of the repair process. Also the usage of mask – exposure on the scanner is modifying the mask surface. Therefore the impact of the mask exposure needs to be investigated, when EUV gets in HVM stage. In the past, the influence of the mask cleaning process on the integrity of EUV mask was investigated, with respect to several lithography-critical parameters as actinic reflectivity, critical dimension (CD) shift, edge roughness and surface roughness. The reparability of the mask was so far not in focus, assuming, that mask can be repaired anytime during its lifetime. This missing item needed for the successful usage of EUV mask needs to be checked and status confirmed prior start of the HVM.

Paper Details

Date Published: 13 July 2017
PDF: 10 pages
Proc. SPIE 10454, Photomask Japan 2017: XXIV Symposium on Photomask and Next-Generation Lithography Mask Technology, 104540P (13 July 2017); doi: 10.1117/12.2278726
Show Author Affiliations
Pavel Nesládek, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Alexander Lajn, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Thorsten Schedel, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)
Markus Bender, Advanced Mask Technology Ctr. GmbH & Co. KG (Germany)


Published in SPIE Proceedings Vol. 10454:
Photomask Japan 2017: XXIV Symposium on Photomask and Next-Generation Lithography Mask Technology
Kiwamu Takehisa, Editor(s)

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