Ion implantation

When forming shallow p-type junctions, what is the main purpose of implanting carbon or similar species together with boron (co-implantation)?

  1. ATo change p-type into n-type
  2. BTo make the wafer emit light
  3. CTo suppress boron diffusion and keep the junction shallow
Show answer and explanation

Answer: C. To suppress boron diffusion and keep the junction shallow

Boron diffusion is enhanced with the help of interstitial silicon (transient enhanced diffusion). Co-implanted carbon traps interstitial silicon, suppressing boron diffusion so the junction stays shallow after annealing.

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More Ion implantation questions

  1. Which gas is typically used in the ion source of an implanter to produce boron ions?
  2. Which is an example of an application of high-energy ion implantation reaching several MeV?
  3. 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?
  4. Which ion implantation is used for wafer splitting (Smart Cut) and for lifetime control in power devices?
  5. When an amorphized layer is recrystallized, what are the defects called that remain slightly deeper than the original boundary between the amorphous layer and the crystal?