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513.160 Microelectronics and Micromechanics | |
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Limited source diffusionThe diffusion equation is, $\large \frac{\partial C}{\partial t}= D\nabla^2C$ . If a limited source of dopants is deposited in a thin layer with a thickness $w$ at the surface such that the dose $Q$ in dopants per square meter is $Q=\int\limits_0^w dz$, the concentration as a function of time $\large C(z,t)=\frac{Q\exp\left(\frac{-z^2}{4Dt}\right)}{\sqrt{4\pi Dt}}$. The concentration falls at the surface and the total number of dopants remains constant.
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