Ion implantation

Which element, heavier than boron, has been considered and used as a p-type dopant to create steep retrograde profiles in nMOS channels?

  1. AIndium
  2. BArsenic
  3. CPhosphorus
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Answer: A. Indium

Indium is a group III acceptor that is much heavier than boron and diffuses slowly, so it stops at shallow depths and keeps a steep profile after heat treatment. It was therefore used to create retrograde channel profiles, low at the surface and high slightly deeper. Its drawback is that it is hard to activate.

  • A. Correct. It is a heavy, slowly diffusing p-type dopant.
  • B. Arsenic is an n-type dopant.
  • C. Phosphorus is an n-type dopant.
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More Ion implantation questions

  1. What problem tends to arise when removing photoresist that has received a high-dose ion implant?
  2. In ion implantation, which parameter mainly determines how deep the dopants are implanted (the range)?
  3. What is the main purpose of annealing (heat treatment) after ion implantation?
  4. Which is a common way to suppress channeling (ions traveling too deep through gaps in the crystal) in ion implantation?
  5. Which unit is used for the dose in ion implantation?