Oxidation and diffusion

Once the oxide has become sufficiently thick in thermal oxidation, how does its thickness relate to oxidation time?

  1. AThickness is roughly proportional to the square root of time (parabolic law)
  2. BThickness is proportional to the square of time
  3. CThickness is constant regardless of time
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Answer: A. Thickness is roughly proportional to the square root of time (parabolic law)

According to the Deal-Grove model, while the oxide is thin the interface reaction limits growth and thickness is roughly proportional to time (linear law). As the film thickens, diffusion of the oxidant through it becomes limiting, and thickness becomes roughly proportional to the square root of time (parabolic law). The thicker the oxide, the slower it grows.

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More Oxidation and diffusion questions

  1. Why does oxide on silicon appear in different colors depending on its thickness?
  2. Which equipment is commonly used to thermally oxidize many wafers at once?
  3. In thermal diffusion, what is the step called that drives dopants deeper after a fixed amount has been introduced at the surface?
  4. How does the thermal oxidation rate of silicon depend on crystal orientation?
  5. What is the main purpose of introducing nitrogen into the gate oxide to make an oxynitride (SiON)?