Silicon wafers

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?

  1. AGettering sites
  2. BThermal donors
  3. CDeep acceptors
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Answer: B. Thermal donors

Heat-treating CZ silicon containing interstitial oxygen at about 350 to 500 °C forms small oxygen clusters that release electrons and act as donors. These are called thermal donors, and especially in lightly doped p-type wafers they can change the resistivity greatly or even convert it to n-type. They can be eliminated by heat treatment at about 650 °C or above.

  • A. Gettering sites are places that capture impurities.
  • B. Correct. Oxygen clusters act as donors.
  • C. They act as donors, not acceptors.
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More Silicon wafers questions

  1. 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?
  2. What are the very gentle undulations on a wafer surface, with lateral wavelengths of a few millimeters and heights of tens of nanometers, called?
  3. Compared with FZ silicon, how does the interstitial oxygen in CZ silicon affect the wafer's mechanical strength?
  4. Which is a known effect of adding a trace of nitrogen during CZ crystal growth (nitrogen doping)?
  5. Which method selectively and shallowly etches defect regions so that dislocations and stacking faults in silicon can be observed with an optical microscope?