Silicon wafers

When finishing a CZ pull, why is the ingot diameter gradually reduced (a tail cone is formed) before separating it from the melt?

  1. ATo raise the oxygen concentration
  2. BTo prevent slip dislocations caused by thermal shock from sudden separation from spreading into the crystal
  3. CTo make the ingot lighter
Show answer and explanation

Answer: B. To prevent slip dislocations caused by thermal shock from sudden separation from spreading into the crystal

Separating the crystal from the melt at full diameter causes thermal stress from the sudden temperature change, generating dislocations that propagate up into the part that becomes product. Gradually narrowing the diameter before separation prevents this generation and propagation.

  • A. It is not meant to raise the oxygen concentration.
  • B. Correct. It prevents dislocations from thermal shock.
  • C. Lightening the ingot is not the purpose.
Practice this topic Back to topic

More Silicon wafers questions

  1. Which is closest to the typical concentration of interstitial oxygen in silicon crystals grown by the CZ method?
  2. In the mirror polishing (final CMP polishing) of silicon wafers, what is commonly used as the abrasive in the slurry?
  3. What is the main use of low-resistivity n⁺ silicon wafers heavily doped with arsenic or antimony?
  4. When CZ silicon is heat-treated around 450 °C, oxygen atoms can cluster and act as donors, changing the wafer's resistivity. What is this called?
  5. To analyze metal contamination on a wafer surface with high sensitivity, which preparation method dissolves the surface oxide with hydrofluoric acid vapor and collects it in a droplet for analysis?