Fabricating a semiconductor device with buried oxide

Claim 1

A method for fabricating, buried oxide integrated circuit devices which comprises: providing a semiconductor substrate having a first epitaxial layer at a surface thereof; forming an implant mask over selected regions of the first epitaxial layer, thereby leaving unmasked regions therein; implanting oxygen into the unmasked regions of the first epitaxial layer to form a buried oxide region therein; selectively applying a second epitaxial layer on the first epitaxial layer over the buried oxide region; forming an extrinsic base region by selectively applying conductivity determining impurities into the second epitaxial layer; diffusing the impurities through the second epitaxial layer and the first epitaxial layer down to the buried oxide; forming an intrinsic base region by selectively applying conductivity determining impurities into the first epitaxial layer adjacent to the extrinsic base region; and forming an emitter region by selectively applying conductivity determining impurities into the intrinsic base region.

Claim 2

A method for fabricating, buried oxide integrated circuit devices which comprises: providing a semiconductor substrate having a first epitaxial layer at a surface thereof; forming an implant mask over selected regions of the first epitaxial layer, thereby leaving unmasked regions therein; implanting oxygen into the unmasked regions of the first epitaxial layer to form a buried oxide region therein; selectively applying a second epitaxial layer on the first epitaxial layer over the buried oxide region; forming an extrinsic base region by selectively applying conductivity determining impurities into the second epitaxial layer; diffusing the impurities through the second epitaxial layer and the first epitaxial layer down to the buried oxide; forming an intrinsic base region by selectively applying conductivity determining impurities into the first epitaxial layer adjacent to the extrinsic base region; and forming an emitter region by selectively applying conductivity determining impurities into the intrinsic base region.

Claim 3

A method for fabricating a, buried oxide integrated circuit device with a polysilicon emitter, comprising: forming a buried layer region in a silicon substrate; applying a first epitaxial layer overlying the buried layer region and a major surface of the silicon substrate; applying a layer of polysilicon overlying a portion of the first epitaxial layer; forming an implant mask over selected regions of the polysilicon and first epitaxial layer, thereby leaving unmasked regions therein; implanting oxygen into the unmasked regions of the first epitaxial layer to form the buried oxide region therein; selectively applying a second epitaxial layer over the buried oxide region; forming an extrinsic base region by selectively applying conductivity determining impurities into the second epitaxial layer; diffusing the impurities through the second epitaxial layer and the first epitaxial layer down to the buried oxide; forming an intrinsic base region by selectively applying conductivity determining impurities through the polysilicon layer and into the first epitaxial layer adjacent to the extrinsic base region; forming an emitter region by selectively applying conductivity determining impurities into the polysilicon layer above the intrinsic base region; forming a collector region by selectively applying conductivity determining impurities into the first epitaxial layer over the buried layer region.

Claim 4

A method for fabricating a, buried oxide integrated circuit device with a polysilicon emitter, comprising: forming a buried layer region in a silicon substrate; applying a first epitaxial layer overlying the buried layer region and a major surface of the silicon substrate; applying a layer of polysilicon overlying a portion of the first epitaxial layer; forming an implant mask over selected regions of the polysilicon and first epitaxial layer, thereby leaving unmasked regions therein; implanting oxygen into the unmasked regions of the first epitaxial layer to form the buried oxide region therein; selectively applying a second epitaxial layer over the buried oxide region; forming an extrinsic base region by selectively applying conductivity determining impurities into the second epitaxial layer; diffusing the impurities through the second epitaxial layer and the first epitaxial layer down to the buried oxide; forming an intrinsic base region by selectively applying conductivity determining impurities through the polysilicon layer and into the first epitaxial layer adjacent to the extrinsic base region; forming an emitter region by selectively applying conductivity determining impurities into the polysilicon layer above the intrinsic base region; forming a collector region by selectively applying conductivity determining impurities into the first epitaxial layer over the buried layer region.

Claim 5

A method for fabricating, buried oxide integrated circuit devices which comprises: providing a semiconductor substrate having an epitaxial layer at a surface thereof; forming an implant mask over selected regions of the epitaxial layer, thereby leaving unmasked regions therein; implanting oxygen into the unmasked regions of the epitaxial layer to form a buried oxide region therein; forming an extrinsic base region by selectively applying conductivity determining impurities into the epitaxial layer above the buried oxide region; depositing a layer of polysilicon over the extrinsic base region; diffusing the impurities through the epitaxial layer down to the buried oxide, and up through portions of the polysilicon layer; selectively etching an undoped portion of the polysilicon layer; and oxidizing the remaining polysilicon to form a layer of silicon dioxide.

Claim 6

A method for fabricating, buried oxide integrated circuit devices which comprises: providing a semiconductor substrate having an epitaxial layer at a surface thereof; forming an implant mask over selected regions of the epitaxial layer, thereby leaving unmasked regions therein; implanting oxygen into the unmasked regions of the epitaxial layer to form a buried oxide region therein; forming an extrinsic base region by selectively applying conductivity determining impurities into the epitaxial layer above the buried oxide region; depositing a layer of polysilicon over the extrinsic base region; diffusing the impurities through the epitaxial layer down to the buried oxide, and up through portions of the polysilicon layer; selectively etching an undoped portion of the polysilicon layer; and oxidizing the remaining polysilicon to form a layer of silicon dioxide.