Blue-X – Exploring wavelength reduction (2–7 nm range) beyond EUV

>"The presentation outlined Blue-X as an industry-wide initiative exploring wavelength reduction (2–7 nm range) as a complementary path to extending Moore’s Law beyond High-NA EUV.

The talk began by positioning the Blue-X approach relative to proposals for increasing numerical aperture beyond High-NA EUV. By selecting a wavelength of 3.1 nm and an NA of 0.27, we demonstrated that a depth of focus of ~43 nm and k₁ ≈ 0.6 can be achieved for resolving 7 nm half-pitch metal nodes projected for the mid-2030s. Unlike Hyper-NA, which faces increasing challenges in depth of focus, mask 3D effects, and cost of ownership, Blue-X leverages wavelength scaling—historically the primary driver of lithographic advancement.

The Blue-X TWG consortium now includes more than 75 member organizations and over 220 assignees representing chip makers, OEMs, national laboratories, universities, and consultants. Eleven sub-TWGs, led by recognized technology leaders, are actively evaluating optics, plasma and FEL photon sources, resist and patterning, masks, optical constants, and scanner design. The initial focus on resist exposure at 6.7 nm has shifted to 3.1 nm, with ongoing resist evaluations at Berkeley Lab and planned open-frame and interference lithography exposures at PSI beginning mid-2026.

Key technical highlights included:

o Multilayer (ML) optics in the water window region, with Sc/Cr at 3.127 nm selected as the current working baseline.

o Strategies to improve ML reflectivity from ~40% today toward 55–60% through interface control and roughness reduction.

o Plasma source modeling (Ga and Sc) and FEL development efforts, including tunable 2–7 nm capability with narrow bandwidth and reduced out-of-band radiation.

o 6.7 nm resist dose-to-clear values primarily in the 50–150 mJ/cm² range.

o Flare control and MSFR requirements (~20 pm range) for 3.1 nm optics.

o Four proposed paths to reduce stochastics at shorter wavelengths:

o Three-beam lithography (IBM)

o Larger masks (12-inch, 8×) (IBM)

o Dose partitioning

o Image contrast enhancement inspired by soft X-ray microscopy techniques

[...]

The central message is clear:

moving from 13.5 nm to 3.1 nm is not the introduction of a fundamentally new technology stack, but rather a challenging and systematic upgrade building upon the physics, infrastructure, and lessons learned from 193 nm to EUVL.

Blue-X represents a coordinated, pre-competitive industry effort to explore this next wavelength node responsibly and collaboratively."