Silicon wafers

What is the main reason silicon wafers are round?

  1. ABecause square chips are easy to arrange on them
  2. BBecause exposure is impossible unless the wafer is round
  3. CBecause the single crystal is pulled while rotating, so the ingot is cylindrical
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Answer: C. Because the single crystal is pulled while rotating, so the ingot is cylindrical

In the CZ method, the crystal is grown by pulling a seed from the melt while rotating it, so the ingot becomes cylindrical. Slicing it gives round wafers. Arranging square chips on a circle wastes the edge, but the shape follows from how the crystal is made.

  • A. For square chips, a square substrate would waste less.
  • B. Exposure tools do not require round substrates.
  • C. Correct. The growth method makes the ingot cylindrical.
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More Silicon wafers questions

  1. Which pair of Japanese companies holds a large share of the global silicon wafer market?
  2. In the CZ method, what is the purpose of growing a thin neck just after the seed crystal at the start of pulling (necking)?
  3. What causes "slip", a problem when large-diameter wafers are heat-treated at high temperature?
  4. Which is closest to the mass of one silicon wafer 300 mm in diameter and 775 µm thick? (Silicon density is about 2.33 g/cm³.)
  5. Which method has been used to make multicrystalline silicon ingots for solar cells cheaply and in large volumes?