Heterojunction bipolar transistor

A heterojunction bipolar transistor (HBT) device, comprising:

• an n-type collector region disposed within a crystalline silicon (Si) layer that is bounded by shallow trench isolators (STIs);
• a p-type intrinsic base comprising a boron-doped carbon-containing silicon germanium (B+-doped Si1-x1-yGex1Cy) crystal that is disposed on a top surface of said crystalline Si layer and that forms angled facets on interfaces of said crystalline Si layer with said STIs;
• a Ge-rich, crystalline Si1-x2Gex2 layer disposed on said angled facets and not on a top surface of said B+-doped Si1-x1-yGex1Cy crystal;
• and
• an n-type diffusion-doped Si crystalline emitter disposed on said top surface and not on said angled facets of said B+-doped Si1-x1-yGex1Cy crystal.

A method of making a heterojunction bipolar transistor (HBT) device, comprising:

• forming an n-type collector region within a crystalline silicon (Si) layer that is bounded by shallow trench isolators (STIs);
• epitaxially growing a p-type intrinsic base that comprises a boron-doped silicon germanium (B+-doped Si1-x1Gex1) crystal on a top surface of said crystalline Si layer, said B+-doped Si1-x1Gex1 crystal forming angled facets on interfaces of said crystalline Si layer with said STIs;
• depositing a sacrificial layer on a top surface and not on said angled facets of said B+-doped Si1-x1Gex1 crystal;
• epitaxially growing a Ge-rich crystalline Si1-x2Gex2 layer on said sacrificial layer and on said angled facets of said B+-doped Si1-x1Gex1 crystal;
• epitaxially growing a p-type extrinsic base layer comprising a highly B+-doped crystalline Si layer on said Ge-rich crystalline Si1-x2Gex2 layer;
• etching an emitter opening through a central portion of at least said highly B+-doped crystalline Si layer, said Ge-rich crystalline Si1-x2Gex2 layer, and said sacrificial layer to said top surface of said B+-doped Six-x1Gex1 crystal;
• and
• forming an n-type diffusion-doped Si crystalline emitter on said top surface of said B+-doped Si1-x1Gex1 crystal in said emitter opening.

A method of making a heterojunction bipolar transistor (HBT) device, comprising:

• forming an n-type collector region within a crystalline silicon (Si) layer that is bounded by shallow trench isolators (STIs);
• epitaxially growing a p-type intrinsic base that comprises a boron-doped silicon germanium (B+-doped Si1-x1Gex1) crystal on a top surface of said crystalline Si layer, said B+-doped Si1-x1Gex1 crystal forming angled facets that are disposed on interfaces of said crystalline Si layer with said STIs;
• depositing a sacrificial layer on a top surface and not on said angled facets of said B+-doped Si1-x1Gex1 crystal;
• epitaxially growing a Ge-rich crystalline Si1-x2Gex2 layer on said sacrificial layer and on said angled facets of said B+-doped Si1-x1Gex1 crystal;
• epitaxially growing a p-type extrinsic base layer comprising a highly B+-doped crystalline Si layer on said Ge-rich crystalline Si1-x2Gex2 layer;
• forming an insulating layer on said highly B+-doped crystalline Si layer;
• etching an emitter opening through a central portion of said insulating layer, said highly B+-doped crystalline Si layer, said Ge-rich crystalline Si1-x2Gex2 layer, and said sacrificial layer to said top surface of said B+-doped Si1-x1Gex1 crystal;
• epitaxially growing a crystalline Si cap on said top surface of said B+-doped Si1-x1Gex1 crystal;
• forming an n-type doped non-crystalline polysilicon on said crystalline Si cap;
• and
• annealing said n-type doped non-crystalline polysilicon to form an n-type doped crystalline emitter, from which an n-type impurity diffuses into said crystalline Si cap to form an n-type diffusion-doped Si crystalline emitter of said HBT.