Ion implantation

What is the technique of implanting n-type impurities into an already p-type region to lower the net doping or invert the conductivity type called?

  1. AGettering
  2. BPassivation
  3. CCounter-doping (compensation)
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Answer: C. Counter-doping (compensation)

Implanting impurities of the opposite type causes donors and acceptors to cancel each other (compensation), lowering the net carrier concentration; with enough, the conductivity type inverts. It is used for threshold-voltage adjustment and similar, but the total impurity content rises, which tends to lower mobility.

  • A. Gettering captures harmful impurities.
  • B. Passivation protects or deactivates surfaces.
  • C. Correct. Impurities of the opposite type cancel the existing doping.
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More Ion implantation questions

  1. In low-energy implants using decel mode (transporting at high energy and decelerating just before the wafer), what causes the "energy contamination" that requires care?
  2. When implanting near the edge of a mask, why do dopants spread laterally under the mask?
  3. Which pair correctly names the two mechanisms by which implanted ions lose energy in a material?
  4. When implanting aluminum or similar into SiC, why is the wafer often heated to several hundred degrees Celsius during implantation (hot implantation)?
  5. Which element, heavier than boron, has been considered and used as a p-type dopant to create steep retrograde profiles in nMOS channels?