Plot Implant, Predeposition and Diffusion Profiles
Produce a graph of approximate Ion Implant, Predeposition and Diffusion Concentration Profiles
This calculation is not a substitute for proper process simulation in most real-world
cases. This tool can be useful for understanding the dopant diffusion process
and may produce usable results in certain cases. Be aware of the following
real-world conditions which may produce significant error:
The above calculation assumes that the diffusivity is constant in time and space.
This is often true for lower concentrations, but diffusivity usually varies spatially with high concentrations.
Because predeposition introduces dopants at solid-solubility concentration, the warning above nearly always
applies to predepositions, which means that the actual predeposition will be deeper than
given by this calculation, which is a solution to the diffusion equation (Fick's Law).
Advanced Predep Models: These advanced (non-constant D) models for Boron, Arsenic and Phosphorus provide a more realistic diffusion
profile, and also calculate the approximate diffusion depth and sheet resistance. Subsequent diffusion step is not performed
on these profiles. Antimony model not available. Data should be considered approximate, but illustrates the magnitude of
diffusion enhancement at high concentrations. Phosphorus model is not considered reliable.
Ion implants produce crystal damage, which leads to a temporal transient in diffusion.
This transient can magnify the diffusivity by orders of magnitude for a time period following
the implant. The effect is not accounted for in this calculation. This effect can be minimized by
performing a rapid thermal anneal (RTA).
Anealing in an oxidizing ambient (IE: growing an oxide during the anneal) will perturb the
diffusion, and is not considered here.
The implant produced in this calculation is a gaussian, which is a very good approximation to
most real implant profiles. However it does not account for atoms travelling in crystal channels. Still,
the ion implant is a reasonable approximation over a wide variety of conditions, usually with the
<100>-oriented wafer tilted 7 degrees from normal. (often a default for ion implantation)