imec, ASML detail high-NA EUV lithography

Technology News |
By Nick Flaherty

European research institute imec is detailing the development of the first 0.55 numerical aperture high-NA extreme ultraviolet (EUV) lithography tool.

The presentations are being made at the 2022 SPIE Advanced Lithography and Patterning Conference and come from the joint high-NA laboratory operated by imec and Dutch equipment maker ASML.

While conventional NA has enabled 3nm production to go beyond 2nm manufacturing process technology will require a move to high-NA equipment. This in turn will require advances in screening resist and underlayer materials, in photomask technology and metrology.

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The companies have ben working together on the technology for the last five years: ASML, imec to take EUV lithography to high-NA. “imec is partnering with ASML on high-NA technology as ASML is building its first prototype 0.55NA EUV lithography scanner the EXE:5000,” said Luc Van den Hove, CEO of imec. 

“High-NA EUV lithography is projected to print the most critical features needed for beyond 2nm logic chips with fewer patterning steps compared to current 0.33NA EUV lithography. It is our role, in tight collaboration with the global patterning ecosystem, to ensure timely availability of advanced resist materials, photomasks, metrology techniques, (anamorphic) imaging strategies, and patterning techniques – to fully benefit from the resolution gain offered by the High-NA EUV lithography scanner,” he said.

High NA EUV papers

imec has authored or co-authored 12 contributions to this year’s SPIE Advanced Lithography Conference.

Three papers address processes and materials for reduced pattern roughness and defectivity (Papers 12051-7; 12055-4; 12056-28). One of the ways this can be achieved is by deploying thinner resists. imec identifies line-edge roughness (LER) as one of the most critical parameters for patterning lines/spaces with thin resist films and explores the role of angles of illumination and mask conditioning to mitigate this. imec also presents the use of metal-oxide resists and pattern and etch schemes aimed at preventing stochastic print failures.

Feature sizes below 10nm and with resist films of 20nm and below also present new problems for metrology at high throughput.

Some of these include reduced scanning electron microscope (SEM) contrast as well as image resolution. One of the approaches is the use of artificial intelligence for de-noising. Others include the adoption of aberration-corrected SEM and scanning probe metrology. imec is contributing to six papers in these areas. (Papers 12053-2; 12053-3; 12053-5; 12053-22; 12053-43; 12053-64)

EUV mask challenges

There are also mask-specific challenges for high-NA EUV. Kurt Ronse, advanced patterning program director at imec, said that simulation studies by IMEC showed that mask imperfections are set to have an increased impact, indicating that mask design rules need to become tighter.

“These findings allow us to identify mask specifications for high-NA EUV lithography. In addition, together with ASML and our material suppliers, we explore novel materials and architectures for the mask absorber, which carries the pattern,” said Ronse. Three further papers cover these developments (Papers 12051-37; 12051-51; 12051-56).

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