Lithography

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

In immersion lithography, the space between the projection lens and the wafer is filled with water (refractive index about 1.44), which has a higher refractive index than air (about 1). This allows NA above 1, resolving finer patterns with the same 193 nm wavelength.

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More Lithography questions

  1. Which correctly describes double patterning (multiple patterning)?
  2. How does the depth of focus (DOF) generally change when the numerical aperture (NA) of an exposure tool is increased?
  3. Which correctly describes OPC (optical proximity correction)?
  4. What is the purpose of a phase-shift mask?
  5. What is overlay accuracy in lithography?