Lithography

Check the basics of lithography — the resolution formula (k1·λ/NA), the EUV wavelength and positive resist — with multiple-choice questions.

—Your accuracy
0 / 50Questions answered
Practice this topicAll questions in this topic, in random order Weak questionsRetry only the questions you last got wrong

Lithography: key points

Lithography transfers the circuit pattern on a mask (reticle) onto photoresist on the wafer using light. It is the key step that sets the limit of scaling, and exposure tools are among the most advanced semiconductor manufacturing equipment.

Resolution improves with a shorter wavelength λ and a larger numerical aperture NA. ArF excimer laser (193 nm) immersion lithography and EUV lithography with a 13.5 nm wavelength are used for leading-edge products.

All Lithography questions (50)

  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)?
  6. How does the depth of focus (DOF) generally change when the numerical aperture (NA) of an exposure tool is increased?
  7. Which correctly describes OPC (optical proximity correction)?
  8. What is the purpose of a phase-shift mask?
  9. What is overlay accuracy in lithography?
  10. Which is a characteristic of chemically amplified resists?
  11. What is the typical reduction ratio when today's exposure tools (scanners) project the mask pattern onto the wafer?
  12. Which is a characteristic of scanner-type exposure tools?
  13. Which correctly describes masks used in EUV lithography?
  14. Which is the correct general order of lithography steps?
  15. What is the technique called that transfers a pattern by pressing a mold with fine patterns into resist?
  16. Which equipment is mainly used to write the patterns of photomasks (reticles)?
  17. What is the role of the thin membrane (pellicle) stretched over a photomask at a fixed distance?
  18. What is the main purpose of the bottom anti-reflective coating (BARC) applied under resist?
  19. Which correctly describes 'High-NA EUV', developed as the next-generation EUV exposure tool?
  20. Which metric describes nanometer-scale roughness on the sidewalls of fine resist patterns?
  21. Which correctly describes the factor k1 in the resolution formula R = k1 × λ / NA?
  22. What is the main cause of the stochastic fluctuations that are a problem in EUV lithography?
  23. Why are defects buried inside the multilayer of an EUV mask a problem?
  24. What is the range of exposure dose and focus over which pattern dimensions stay within tolerance called?
  25. In LELE (litho-etch-litho-etch) double patterning, what is especially strictly required?
  26. What is the wavelength of the mercury lamp's i-line?
  27. Which technique illuminates the mask from oblique directions to improve the resolution of fine patterns?
  28. Which method develops a positive chemically amplified resist with an organic solvent, dissolving the unexposed areas?
  29. What is an advantage of metal-oxide-containing resists being developed for EUV lithography?
  30. Which patterning technique uses the tendency of block copolymers to form regular fine patterns spontaneously?
  31. What is the role of lithography in semiconductor manufacturing?
  32. What was the original meaning of the word "lithography"?
  33. Which correctly describes photoresist?
  34. Which company is effectively the sole supplier of EUV lithography tools?
  35. What is the wavelength of the light used in KrF excimer laser lithography?
  36. What is the main purpose of treating the wafer surface with HMDS or similar before coating resist?
  37. What does "half-pitch", used as a measure of scaling, mean?
  38. What are the reference marks placed on a wafer so that each exposure can be accurately overlaid on patterns made in earlier steps called?
  39. What does "CDU", controlled in lithography, mean?
  40. What is the material called, used to make photomasks, consisting of a quartz glass substrate pre-coated with a light-blocking film and similar?
  41. Which correctly describes writing patterns directly into resist on the wafer with an electron beam, without a mask?
  42. How is 13.5 nm light generated in the light source of an EUV lithography tool?
  43. What is the process called that removes, with solvent, the resist that builds up around the wafer edge after spin coating?
  44. In current scanner exposure tools, what is the typical maximum area on the wafer that can be exposed in one exposure (one shot)?
  45. Which technique uses computation to jointly optimize the illumination shape of the exposure tool and the mask pattern to improve resolution?
  46. In immersion lithography with very high numerical aperture (NA), why does light polarization need to be considered?
  47. What is the main cause of "flare", a problem in EUV lithography?
  48. 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?
  49. What are the weak spots in a layout called, which lithography or process simulation predicts are prone to patterns bridging or breaking?
  50. Why has gas released from resist (outgassing) been a concern in EUV lithography?

Other topics in Front-end processes