Ion implantation

In ion implantation, how is the dose made uniform across the wafer?

  1. AThe beam is held fixed at one point
  2. BThe beam or the wafer is scanned so the whole wafer is implanted uniformly
  3. CThe wafer is kept heated
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Answer: B. The beam or the wafer is scanned so the whole wafer is implanted uniformly

The ion beam is smaller than the wafer, so the beam is swept with electric or magnetic fields, or the wafer is moved mechanically, scanning the whole surface during implantation. Controlling scan speed and the number of passes reduces dose variation across the wafer.

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More Ion implantation questions

  1. In an ion implanter, which component measures the beam current to determine the number of implanted ions (dose)?
  2. When forming shallow p-type junctions, what is the main purpose of implanting carbon or similar species together with boron (co-implantation)?
  3. Which gas is typically used in the ion source of an implanter to produce boron ions?
  4. Which is an example of an application of high-energy ion implantation reaching several MeV?
  5. If dopants with a dose of 1×10¹⁵ cm⁻² are distributed uniformly over a depth of 100 nm, what is the approximate average concentration?