Oxidation and diffusion

In the Deal-Grove model, what is the relationship between oxide thickness and time early in thermal oxidation, while the oxide is still thin?

  1. AThickness is proportional to the square root of time
  2. BThickness is roughly proportional to time (increases linearly)
  3. CThickness stays constant regardless of time
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Answer: B. Thickness is roughly proportional to time (increases linearly)

While the oxide is thin, oxidants pass through it easily and the reaction rate at the interface is limiting, so thickness grows roughly in proportion to time (the linear law). As the oxide thickens, diffusion of the oxidant through the film becomes limiting and thickness grows with the square root of time (the parabolic law).

  • A. Square-root dependence applies after the oxide becomes thick.
  • B. Correct. Early growth is reaction-limited and linear.
  • C. Thickness increases as oxidation proceeds.
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More Oxidation and diffusion questions

  1. Which generally describes the thickness relationship between the field oxide used for isolation such as LOCOS and the gate oxide of a MOSFET?
  2. What is the common definition of the "junction depth" of a PN junction?
  3. What is the phenomenon called in which boron and phosphorus diffuse faster during silicon oxidation than without oxidation?
  4. When thin oxides of a few tens of nanometers or less are grown by dry oxidation, which known deviation from the Deal-Grove model occurs?
  5. In LOCOS, what is the phenomenon called in which a thin nitride forms on the silicon surface under the nitride mask, later causing the gate oxide there to be locally thin or defective?