Lithography

What is overlay accuracy in lithography?

  1. AThe thickness uniformity of the coated resist
  2. BHow accurately a new pattern can be positioned relative to the pattern formed in a previous step
  3. CVariation in exposure dose
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Answer: B. How accurately a new pattern can be positioned relative to the pattern formed in a previous step

LSIs are built by stacking dozens of pattern layers, so each layer must be precisely aligned to the previous one. How small that misalignment is defines overlay accuracy. The finer the features, the smaller the allowable error, and nanometer-level accuracy is now required.

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More Lithography questions

  1. Which is a characteristic of chemically amplified resists?
  2. What is the typical reduction ratio when today's exposure tools (scanners) project the mask pattern onto the wafer?
  3. Which is a characteristic of scanner-type exposure tools?
  4. Which correctly describes masks used in EUV lithography?
  5. Which is the correct general order of lithography steps?