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What is the difference between arsenic and phosphorus in IC fabrication technology? When do we prefer one of them over the other?

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    \$\begingroup\$ Seemingly this is better to transfer this question to physics forum. \$\endgroup\$ Commented Oct 12, 2022 at 14:32
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    \$\begingroup\$ just delete your question and ask at physics SE \$\endgroup\$
    – jsotola
    Commented Oct 12, 2022 at 15:05
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    \$\begingroup\$ I honestly think semiconductor design and theory is EE. don't really see how "in which EE applications do I need either type of doting" is more on topic over at physics than here. (Also, this is 5th semester course level at multiple EE programs I'm aware of, another indication of brings to the engineering field) \$\endgroup\$ Commented Oct 12, 2022 at 20:30
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    \$\begingroup\$ cityu.edu.hk/phy/appkchu/AP6120/8.PDF \$\endgroup\$ Commented Oct 12, 2022 at 21:34
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    \$\begingroup\$ @mohammadrezza It has to do with the process (recipes, equipment, temperatures and step durations used, etc.) But another factor has to do with safety and handling, as well. While all gases used are usually toxic, arsine is extremely toxic when released in the air and it does NOT degrade with time. It is relatively stable in an oxygen atmosphere. A small canister ($50 worth) can kill about 3000 people. Phosphine is, on the other hand, less toxic but extremely pyrophoric. A terrible fire hazard anytime that stuff is around. Safety is another factor in choice, I suspect. \$\endgroup\$
    – jonk
    Commented Oct 12, 2022 at 23:17

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The answer will depend on the semiconductor. This answer applies to silicon.

Both are n type dopants. So at first you might think they are interchangeable, and to some extent they are. But they have other properties that leads to picking one over the other.

Arsenic is much heavier/bigger than phosphorus. This means it will implant shallower and diffuse less. If you want a very shallow implant, arsenic is your friend. This is probably the biggest difference most people care about.

Other important differences include:

  • How much of the dopant you can activate, which affects maximum effective dopant concentration.
  • Energy of the dopant levels within the bandgap. Arsenic is a moderately deep dopant. Operating at lower temperatures may not fully ionize the arsenic.
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