Lithography

Why has gas released from resist (outgassing) been a concern in EUV lithography?

  1. ABecause the gas always increases resist sensitivity
  2. BBecause it can deposit on and contaminate the optics (mirrors) in vacuum, lowering their reflectivity
  3. CBecause the gas cools the wafer
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Answer: B. Because it can deposit on and contaminate the optics (mirrors) in vacuum, lowering their reflectivity

EUV exposure takes place in vacuum, and exposure causes the resist to release gases, including carbon-containing species. If these deposit on the surfaces of the expensive multilayer mirrors and cause carbon contamination, reflectivity drops and tool performance suffers. Outgassing of EUV resists is therefore evaluated and controlled.

  • A. Increased sensitivity is not the concern.
  • B. Correct. It can contaminate the mirrors and lower reflectivity.
  • C. Cooling the wafer is not the concern.
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More Lithography questions

  1. Based on the resolution formula R = k1 × λ / NA, how can resolution be improved (R made smaller)?
  2. What wavelength of light is used in EUV lithography?
  3. Which correctly describes positive photoresist?
  4. Which correctly describes ArF immersion lithography?
  5. Which correctly describes double patterning (multiple patterning)?