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distripution of impurities in the silicon wafer using diffusion process


Falah Mohammed

Jan 1, 1970
Can anyone explain to me why the distribution of impurity ions takes
either Gaussian or erfc function distribution under thermal diffusion?

Charles Jean

Jan 1, 1970
On 5 Oct 2003 00:45:58 -0700, [email protected] (Falah Mohammed)
Sorry to "answer" your question with another question, but:
Is the distribution EVER Gaussian? When I worked with semiconductor
manufacture, we always assumed that it was erfc, and the empirical
results(junction depth, device characteristics, etc.) were very close
to the erfc distribution. This was boron or phosphorus into 1:1:1
silicon, around 1200 deg. C.
It's been a long time ago, but doesn't the erfc distribution require
diffusion from an "infinite" source at the surface? Our diffusions
were always from a solid solubility of dopant at the surface-as close
to "infinite" as one can get. If the surface concentration of dopant
WERE concentration-limited, would that change the distribution type
from erfc to Gaussian? These are just WAGs, but hope they help.
Maybe a solid-state physicist out there knows and will jump in
here-you've piqued my curiosity.