
513.160 Microelectronics and Micromechanics  

Constant source diffusionThe diffusion equation is, $\large \frac{\partial C}{\partial t}= D\nabla^2C$ . In constant source diffusion, the concentration is held constant at the surface. The concentration of dopants is, $\large C(z,t)=C_0\text{erfc}\left(\frac{z}{\sqrt{4Dt}}\right)$. The concentration remains constant at the surface and the total number of dopants increases as a function of time. 