On solid-state diffusion from a limited source

Diffusion into a solid from a source which is limited in amount is described. It is shown that only in very simple cases Fick's law can be solved analytically for this type of diffusion and that many examples arise in practise which do not fall into this simple category. Examples are taken for which the diffusion coefficient varies as a power of the diffusant concentration, i.e. D ∼ Cn, and a numerical technique is employed to calculate diffusion profiles. In the calculations, experimental data is used, taken from the field of diffusion in semiconductors. The complex boundary conditions which may arise in practise are also considered, in particular those involved in drive-in diffusion and ion-implantation annealing, both of which are important in the semiconductor industry.