EUV vs DUV Lithography: What Is the Difference?

Lithography prints circuit patterns on the wafer with light. DUV (deep ultraviolet) lithography uses 193 nm light from an ArF laser, with lenses and a layer of water between the lens and wafer (immersion). EUV (extreme ultraviolet) lithography uses 13.5 nm light, so it can print far finer patterns in a single exposure, but the light is absorbed by almost everything, so the whole system must be built from mirrors in a vacuum. EUV is far more expensive and complex.

AspectDUV (ArF immersion)EUV
Wavelength193 nm13.5 nm
Light sourceArF excimer laserLaser-produced plasma: a laser hits tiny droplets of molten tin
OpticsLenses (refractive), with water between the last lens and the wafer in immersion systemsOnly mirrors (reflective multilayers), because almost every material absorbs EUV light
PhotomaskTransmissive mask made of quartzReflective mask with a multilayer coating
EnvironmentAir or nitrogen, plus the immersion waterVacuum
ResolutionSingle exposure resolves pitches down to about 80 nm; finer patterns need multiple patterningSingle exposure can print pitches around 30 nm or below; High-NA EUV goes further
Process complexityMultiple patterning (such as SADP, SAQP) multiplies the number of stepsFewer steps for the finest layers, but new challenges in resists and masks
Main defectsOverlay errors and defects from multiple patterningStochastic defects caused by the small number of photons, and mask defects
Tool costTens of millions of dollars per toolWell over a hundred million dollars per tool
SuppliersASML, Nikon and othersASML is effectively the only supplier
Typical useMost layers of most chips, including advanced onesThe most critical, finest layers at roughly the 7 nm class and below

Figures are typical orders of magnitude and vary by process generation and product.

When to use which

DUV
Still prints the large majority of layers, even in leading-edge chips. It is mature, fast and much cheaper per layer.
EUV
Used for the finest critical layers, where DUV would need several patterning steps. It simplifies the process but the tools and operating costs are very high.
Next
High-NA EUV uses a larger numerical aperture to resolve even smaller features for the next nodes.

FAQ

Why does EUV use a 13.5 nm wavelength?

A shorter wavelength prints finer patterns. At 13.5 nm, EUV light is about 14 times shorter than the 193 nm light of ArF DUV, so a single exposure can print features that would need multiple patterning with DUV.

Why are EUV systems so expensive?

The light source is a laser-heated tin plasma, the optics are all multilayer mirrors, and the whole system runs in a vacuum. A single tool costs well over a hundred million dollars.

Who makes EUV lithography machines?

ASML is effectively the only supplier of EUV lithography tools.

Has EUV replaced DUV?

No. Most layers, even in advanced chips, are still printed with DUV. EUV is used for the finest, most critical layers.

Check your understanding

What wavelength of light is used in EUV lithography?

  1. A193 nm
  2. B248 nm
  3. C13.5 nm
Show answer and explanation

Answer: C. 13.5 nm

EUV (extreme ultraviolet) lithography uses 13.5 nm light—about 1/14 of ArF's wavelength—to print fine patterns in a single exposure. Since nearly all materials, including air and glass, absorb it, EUV uses reflective optics of Mo/Si multilayer mirrors instead of lenses and operates in vacuum. Each mirror reflects only about 70%, so after nearly ten mirrors most light is lost and a very powerful source is needed.

Which correctly describes ArF immersion lithography?

  1. AThe whole wafer is submerged in water for development
  2. BThe resist is diluted with water before coating
  3. CThe space between the projection lens and the wafer is filled with water to increase the numerical aperture (NA)
Show answer and explanation

Answer: C. The space between the projection lens and the wafer is filled with water to increase the numerical aperture (NA)

Immersion lithography fills the roughly 1 mm gap between the final lens and wafer with ultrapure water (refractive index about 1.44 at 193 nm) instead of air (about 1). Since NA = n·sinθ, NA can exceed 1 (up to 1.35), resolving finer patterns at the same 193 nm wavelength. Introduced to production around 2006, it required nozzles that hold water in place under fast wafer motion and resist topcoats that resist water penetration.

Which correctly describes 'High-NA EUV', developed as the next-generation EUV exposure tool?

  1. AThe numerical aperture of the projection optics was increased from 0.33 to 0.55 to improve resolution
  2. BThe exposure wavelength was lengthened to 193 nm
  3. CIt exposes without a mask
Show answer and explanation

Answer: A. The numerical aperture of the projection optics was increased from 0.33 to 0.55 to improve resolution

Standard EUV scanners have an NA of 0.33; High-NA EUV raises it to 0.55, improving resolution about 1.7× and enabling single-exposure patterning of pitches in the low 20 nm range at the same 13.5 nm wavelength. Depth of focus shrinks, and because reduction differs by direction, the exposure field is halved. Developed by ASML, each tool is reported to cost on the order of hundreds of millions of dollars.

  1. What is the main cause of the stochastic fluctuations that are a problem in EUV lithography?
  2. Which company is effectively the sole supplier of EUV lithography tools?
  3. Which correctly describes masks used in EUV lithography?

Practice Lithography questions

Key terms explained

EUV lithography
Lithography using extreme ultraviolet light with a wavelength of 13.5 nm. It uses reflective optics and a vacuum environment.
Immersion lithography
Exposure with the space between the lens and the wafer filled with water. It allows a numerical aperture above 1, so ArF excimer lasers can form finer patterns.
High-NA EUV
Next-generation EUV lithography that raises the projection optics' numerical aperture from 0.33 to 0.55 to improve resolution.

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