Thermal migration-porous silicon technique for forming deep dielectric isolation

摘要

A method for forming deep dielectric isolation regions of uniform porous silicon dioxide in silicon wafers having 100 face planes. Subcollector regions of one conductivity type are placed in a silicon substrate of opposite conductivity type. The substrate is covered by an epi layer of the opposite conductivity type. Isolation patterns of heavily doped impurity of the substrate conductivity type are thermally migrated along 110 and 110 crystallographic planes deeply and uniformly through the epi layer and into the substrate between the subcollector regions. The doped isolation patterns are converted to porous silicon by anodic treatment, and the porous silicon is converted into porous silicon dioxide by exposure to an appropriate oxidizing atmosphere.