Lithography

What is the main cause of "flare", a problem in EUV lithography?

  1. ASlight roughness of mirror surfaces scatters light so that it reaches areas that should be dark
  2. BThe resist burning
  3. CThe wafer rotating
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Answer: A. Slight roughness of mirror surfaces scatters light so that it reaches areas that should be dark

Because the EUV wavelength is very short, even atomic-scale roughness on mirror surfaces scatters light. The scattered light spreads over areas that should be dark, lowering image contrast and causing dimensional variation. This is called flare and is handled with corrections that depend on pattern density, among other measures.

  • A. Correct. Light scattered by mirror surface roughness is the cause.
  • B. It is not the resist burning.
  • C. Wafer rotation is irrelevant.
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More Lithography questions

  1. In EUV masks, what is the phenomenon called in which the absorber pattern's thickness is not negligible compared with the wavelength, so obliquely incident light casts shadows and otherwise affects the image?
  2. What are the weak spots in a layout called, which lithography or process simulation predicts are prone to patterns bridging or breaking?
  3. Why has gas released from resist (outgassing) been a concern in EUV lithography?
  4. Based on the resolution formula R = k1 × λ / NA, how can resolution be improved (R made smaller)?
  5. What wavelength of light is used in EUV lithography?