Ion implantation

What is used to suppress wafer charging (charge-up) during ion implantation?

  1. AHeating the wafer to high temperature
  2. BMaximizing the beam current
  3. CDevices that supply electrons to neutralize charge (such as a plasma flood gun)
Show answer and explanation

Answer: C. Devices that supply electrons to neutralize charge (such as a plasma flood gun)

Continuously implanting positive ions charges insulated areas on the wafer, which can destroy gate oxides. Plasma flood guns and electron showers supply low-energy electrons near the wafer to neutralize the positive charge.

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More Ion implantation questions

  1. Singly charged ions are implanted into a wafer area of 100 cm² at a dose of 1×10¹⁵ ions/cm². With a beam current of 1 mA, approximately how long does the implant take? (Elementary charge 1.6×10⁻¹⁹ C)
  2. In CMOS well formation, what is a well called in which high-energy implantation makes the dopant concentration higher deep below the surface?
  3. What is the main purpose of halo (pocket) implants, which implant dopants of the same type as the channel at an angle near the source/drain edges?
  4. Why is BF2⁺ sometimes implanted instead of boron alone to form shallow p-type layers?
  5. What is the phenomenon called in which diffusion of boron and other dopants is temporarily accelerated early in annealing because of interstitial silicon created by implantation?