Diffusion in SiO2



        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.