Oxidation and diffusion

When boron-doped silicon is thermally oxidized, how does the boron concentration on the silicon side near the interface tend to change?

  1. AIt decreases, because boron is readily taken into the oxide
  2. BIt increases, because boron is pushed out to the interface
  3. CIt does not change
Show answer and explanation

Answer: A. It decreases, because boron is readily taken into the oxide

At the Si/SiO2 boundary, each dopant has a characteristic ratio in which it divides between the two sides (segregation). Boron is readily taken into the oxide, so its concentration near the silicon surface decreases. Phosphorus and arsenic, in contrast, are pushed into the silicon and tend to pile up near the interface.

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More Oxidation and diffusion questions

  1. What is the heat treatment called that heats wafers one at a time to high temperature for a few seconds using lamps or similar sources?
  2. Which value is closest to the relative permittivity of SiO2 formed by thermal oxidation?
  3. Which is one of the major reasons silicon has been so widely used as a material for MOS devices?
  4. What problem occurs when mobile ions such as sodium are present in the gate oxide?
  5. Which n-type dopant diffuses relatively slowly in silicon during heat treatment, making shallow junctions easier to form?