Masking Properties of Silicon Dioxide
of the most important properties of silicon dioxide is its ability to mask
impurities during high-temperature diffusion.
diffusivities of antimony, arsenic, boron and phosphorous in silicon
dioxide are all orders of magnitude smaller than their corresponding
values in silicon. Thus silicon dioxide can be used effectively to mask
deep diffusion can take place in unprotected regions of silicon, whereas
no significant impurity penetration will occur in regions covered by
Fig. 4 Diffusion masking oxide.