Locus isolation technique using high pressure oxidation (hipox) and protective spacers

摘要

A technique for producing an isolation structure in a semiconductor substrate wherein lateral encroachment, i.e., bird's beak formation, under a masking stack is limited. The disclosed embodiment comprises growing a layer of pad oxide on a silicon substrate and then depositing a layer of silicon nitride on the layer of pad oxide. The nitride is then patterned and etched to define a masking stack and a region of the substrate wherein the isolation structure is to be formed. The pad oxide is then removed from the region and is also partially removed under the nitride stack, thus forming a cavity. A re-ox oxide layer is then grown over the substrate, followed by the growth of a spacer layer. The spacer layer is comprised of either polysilicon or silicon nitride. Subsequently, the isolation structure is grown using high pressure oxidation techniques, which results in the oxidation structure growing sufficiently fast that the spacer layer in the cavity is not oxidized. Lateral encroachment is thus reduced and punchthrough of the bird's beak region is prevented.