Deep boron diffusion

The deep boron diffusion process allows a boron concentration of up to 1e20 atoms/cm^3 to be attained at a depth of up to 15 µm (silicon substrate). The heavily doped layer may then be used as an etch stop layer to define membranes, cantilevers or other features in a subsequent anisotropic wet etch. The diffusion can also be masked using a patterned oxide layer if localization of the doping is required.