Lithography

What is the process called that removes, with solvent, the resist that builds up around the wafer edge after spin coating?

  1. AAshing
  2. BEdge bead removal
  3. CPost-exposure bake
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Answer: B. Edge bead removal

Spin coating leaves a thick rim of resist around the wafer edge due to surface tension (the edge bead). Left in place, it can flake off during handling as particles or contaminate tools, so solvent is directed at the edge to remove it.

  • A. Ashing removes all resist with plasma or similar.
  • B. Correct. It removes the built-up resist at the edge.
  • C. A post-exposure bake is a heat treatment after exposure.
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