Oxidation and diffusion

When an SiO2 film of thickness x is formed by thermally oxidizing silicon, approximately how much silicon is consumed?

  1. AAbout 0.44x
  2. BAbout 1.0x
  3. CAbout 2.2x
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Answer: A. About 0.44x

In thermal oxidation, silicon itself reacts with oxygen to become SiO2. From the densities and molecular weights of Si and SiO2, forming oxide of thickness x consumes about 0.44x of silicon. About 44% of the oxide therefore lies below the original silicon surface and the rest above it.

Oxide growth by thermal oxidation Before Silicon After SiO₂ (thickness x) Silicon Original surface about 0.56x about 0.44x About 44% of the oxide thickness comes from consumed silicon
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More Oxidation and diffusion questions

  1. How does the diffusion coefficient of dopants in silicon depend on temperature?
  2. Which method is mainly used for device isolation in scaled LSIs?
  3. Once the oxide has become sufficiently thick in thermal oxidation, how does its thickness relate to oxidation time?
  4. Why does oxide on silicon appear in different colors depending on its thickness?
  5. Which equipment is commonly used to thermally oxidize many wafers at once?