· Diffusion in SiO2 films is important as it is used as a mask to prevent diffusion of impurity atoms in silicon
· Group III and Group V elements are glass formers in SiO2 and so lower the melting temperatures of the oxide film.
· As a general rule, over the temperature used in VLSI, diffusivities of B, As, P and Sb are very low when their concentrations are below that which causes the glass to melt.
· Hydrogen, He, OH, Na, O2 and Ga are fast diffusants in SiO2.
· SIMS analysis is a powerful tool for diffusion profile measurements. It can measure boron and arsenic concentrations as low as 5X1015 atoms /cm3, and has a high depth resolution of a few tens of angstroms. Therefore it is an ideal tool for measuring shallow diffusion profiles.