Oxidation and diffusion

Why can thermal oxide be used as a mask against dopants during diffusion?

  1. ABecause many dopants, such as boron and phosphorus, diffuse more slowly in SiO2 than in silicon
  2. BBecause SiO2 conducts electricity well
  3. CBecause SiO2 does not transmit light
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Answer: A. Because many dopants, such as boron and phosphorus, diffuse more slowly in SiO2 than in silicon

Major dopants such as boron, phosphorus and arsenic diffuse much more slowly in SiO2 than in silicon, so a sufficiently thick oxide prevents them from reaching the silicon below. This property has been used for selective diffusion, introducing dopants only through windows opened in the oxide.

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More Oxidation and diffusion questions

  1. What is the heat treatment called, performed in a hydrogen-containing atmosphere to reduce interface states at the Si/SiO2 interface?
  2. What is the main purpose of adding a small amount of chlorine-containing gas such as hydrogen chloride (HCl) during thermal oxidation?
  3. When boron-doped silicon is thermally oxidized, how does the boron concentration on the silicon side near the interface tend to change?
  4. 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?
  5. Which value is closest to the relative permittivity of SiO2 formed by thermal oxidation?