Ion implantation

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?

  1. AIons neutralized before deceleration reaching the wafer at high energy because they are not decelerated
  2. BThe wafer temperature being too low
  3. CThe mass-analysis magnet being too strong
Show answer and explanation

Answer: A. Ions neutralized before deceleration reaching the wafer at high energy because they are not decelerated

In decel mode, the beam is transported at high energy and decelerated at the end for a low-energy implant. Particles neutralized along the way, for example by gas collisions, are not decelerated by the field, so they arrive at high energy and place dopants deeper than intended. For shallow junctions, this is suppressed with good beamline vacuum and filtering.

  • A. Correct. Neutralized particles arrive without being decelerated.
  • B. Wafer temperature is not the cause of energy contamination.
  • C. The strength of mass analysis is not the cause.
Practice this topic Back to topic

More Ion implantation questions

  1. When implanting near the edge of a mask, why do dopants spread laterally under the mask?
  2. Which pair correctly names the two mechanisms by which implanted ions lose energy in a material?
  3. When implanting aluminum or similar into SiC, why is the wafer often heated to several hundred degrees Celsius during implantation (hot implantation)?
  4. Which element, heavier than boron, has been considered and used as a p-type dopant to create steep retrograde profiles in nMOS channels?
  5. What problem tends to arise when removing photoresist that has received a high-dose ion implant?