Redistribution of simple impurities during oxide growth:

During oxide growth some of the impurity doped silicon is consumed which results in redistribution of impurities. The extent of this redistribution is the function of the rate at which the silicon is consumed and of the relative diffusivities and solid solubility of the impurities in silicon and $SiO_2$. Value of distribution constant (m) is about 20 for gallium and 10 for arsenic, antimony and phosphorus.

Diffusion during oxide growth:

The surface oxidation of silicon results in the enhanced diffusion of most group III and group V dopants with exception of antimony. This enhancement is due to the creation of self-interstitials during the oxidation process. It is most significant in case of boron in silicon.

Co-operative diffusion effects:

It was first observed in BJT fabrication, where it resulted in enhanced diffusion under the emitter, sometimes referred to as emitter push effect.