Process for fabricating isolation structure for IC featuring grown and buried field oxide

摘要

An isolation structure having both deep and shallow components is formed in a semiconductor workpiece by etching the workpiece to define raised precursor active device regions separated by sunken precursor isolation regions. An oxidation mask is formed to expose the precursor isolation regions, and the unmasked precursor isolation regions are exposed to oxidizing conditions to grow field oxides as the deep isolation component. Thermal growth of these field oxides creates topography which includes shallow recesses adjacent to the raised precursor active device regions. Deposition of conformal dielectric material such as high density plasma (HDP) deposited silicon oxide over the entire surface and within the recesses creates the shallow isolation component. Following planarization of the conformal dielectric material, fabrication of the device is completed by introducing conductivity-altering dopant into raised precursor active device regions. Vertical isolation of the device from the underlying material is provided by a subsurface dielectric or doped layer in contact with the deep isolation component.