Advanced packaging (3D and chiplets)

Which method is used to make silicon interposers larger than the maximum area a lithography tool can expose at once (about 26 mm × 33 mm)?

  1. AExposing with wiring joined across the boundaries of multiple shots (stitching)
  2. BEnlarging the exposure tool's lens
  3. CConnecting interposers with wire bonding
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Answer: A. Exposing with wiring joined across the boundaries of multiple shots (stitching)

The area of a single exposure shot (the reticle size) is limited to about 26 mm × 33 mm. AI packages need interposers several times that size to hold a GPU and many HBM stacks. Stitching exposure, which precisely joins wiring across the boundaries of adjacent shots, is therefore used to make interposers larger than the reticle size.

  • A. Correct. Shots are joined to expose a large area.
  • B. Enlarging lenses is not the solution; the exposure field is fixed by tool standards.
  • C. Wire bonding cannot achieve the fine wiring density of an interposer.
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