Ion implantation

What is the typical distribution of crystal damage created by ion implantation?

  1. AIt is concentrated only at the surface
  2. BIt is concentrated at the back of the wafer
  3. CIt forms mostly around the depth where ions stop (the range) and slightly shallower
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Answer: C. It forms mostly around the depth where ions stop (the range) and slightly shallower

While fast, ions lose energy mainly through interactions with electrons; as they slow down, they start knocking atoms out through nuclear collisions. Crystal damage therefore forms mostly around the range where ions stop and slightly before it.

  • A. Damage extends down to around the range, not just the surface.
  • B. Implantation is done from the front, so it does not reach the back.
  • C. Correct. It forms mostly around and slightly before the range.
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More Ion implantation questions

  1. What method has commonly been used to introduce impurities into a MOSFET's polysilicon gate electrode to lower its resistance?
  2. 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?
  3. 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?
  4. When implanting near the edge of a mask, why do dopants spread laterally under the mask?
  5. Which pair correctly names the two mechanisms by which implanted ions lose energy in a material?