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During predeposition, what parameter controls the concentration of dopant at the surface of the wafer?

During predeposition, what parameter controls the concentration of dopant at the surface of the wafer?

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Answer #1

Predeposition is also called as the constant source diffusion because in this the impurity is held constant at the surface of the wafer. The impurity concentration as a function of depth and time is given as -

The surface concentration N0 remains constant, and the diffusion moves deeper into silicon wafer as Dt product increases. Dt can change as a result of increasing diffusion time, increasing diffusion temperature, or a combination of both.

An external impurity source must supply a continual flow of impurity atoms to the surface of the wafer. And the depth is controlled by the diffusivity D.

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