Cleaning of MoSi multilayer mask blanks for EUVL

Vivek Kapila; Abbas Rastegar; Yoshiaki Ikuta; Sean Eichenlaub; Pat Marmillion

doi:10.1117/12.686556

20 October 2006 Cleaning of MoSi multilayer mask blanks for EUVL

Vivek Kapila, Abbas Rastegar, Yoshiaki Ikuta, Sean Eichenlaub, Pat Marmillion

Proceedings Volume 6349, Photomask Technology 2006; 63492W (2006) https://doi.org/10.1117/12.686556
Event: SPIE Photomask Technology, 2006, Monterey, California, United States

Abstract

Extreme ultraviolet lithography (EUVL) is being considered as the enabler technology for the manufacturing of future technology nodes (30 nm and beyond). EUV mask blanks are Bragg mirrors made of Mo and Si bilayers and tuned for reflectivity at a wavelength λ ~13 nm. Implementation of EUVL requires that the mask blanks be free of defects at 30 nm or above. However, during the deposition of MoSi multilayers and later during the handling of blanks, defects are added to the blank. Therefore, the cleaning of EUV mask blanks is a critical step in the manufacturing of future devices. The particulate defects on the multilayer-coated mask blanks can either be embedded in or under the MoSi layers or adhered to the top capping layer during the deposition process. The defects can also be added during the handling of photomasks. Our previous studies have shown successful removal of the handling-related defects at SEMATECH's Mask Blank Development Center (MBDC) in Albany, NY. However, cleaning embedded and adhered defects presents new challenges. The cleaning method should not only be able to remove the particles, but also be compatible with the mask blank materials. This precludes the use of any aggressive chemistry that may change the surface condition leading to diminished mask blank reflectivity. The present work discusses the recent progress made at SEMATECH's MBDC in cleaning backside Cr-coated mask blanks with a MoSi multilayer and a Si cap layer on the top surface. Here we present our data that demonstrates successful removal of sub-100 nm particles added by the deposition process. Surface morphology and defect composition on the surface of the MoSi multilayer are discussed. EUV reflectivity measurements and atomic force microscopy (AFM) images of the mask blank before and after cleaning are presented. The present data shows that no measurable damage to the EUV mask blank is caused by the cleaning processes developed at the MBDC.

Citation Download Citation

Vivek Kapila, Abbas Rastegar, Yoshiaki Ikuta, Sean Eichenlaub, and Pat Marmillion "Cleaning of MoSi multilayer mask blanks for EUVL", Proc. SPIE 6349, Photomask Technology 2006, 63492W (20 October 2006); https://doi.org/10.1117/12.686556

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