Question: What is diffusion?
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Subject: Electronics Engineering

Topic: IC Technology

Difficulty: Medium / High

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modified 8 weeks ago  • written 8 weeks ago by gravatar for Sayali Bagwe Sayali Bagwe1.9k
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It is the process of introduction of dopant atoms into the semiconductor. It alters the type of conductivity of the semiconductor.

Diffusion is the movement of impurity atoms in a semiconductor material at high temperatures.

Diffusion is applied to anneal the crystal defects after ion implantation or to introduce dopant atoms into silicon from a chemical vapor source. In the last case the diffusion time and temperature determine the depth of dopant penetration.

Diffusion is used to form the source, drain, and channel regions in a MOS transistor. But diffusion can also be an unwanted parasitic effect, because it takes place during all high temperature process steps.

Methods – Diffusion from a

  1. Chemical source
  2. Doped oxide source
  3. Diffusion and annealing from an ion implanted layer

Advantages:

  1. No crystal damage like its alternatives.
  2. Batch processing (handling many wafers in single process) is possible.
  3. High quality junction with minimum leakage current is possible.

Disadvantages:

  1. High temperature method
  2. It cannot independently control the dopant concentration and junction depth.
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written 8 weeks ago by gravatar for Sayali Bagwe Sayali Bagwe1.9k
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