Efficiently fabricated bipolar transistor
View Patent ↗One embodiment is a method for fabricating the base of a bipolar transistor where the method comprises placing a first wafer in an undoped epi chamber. Next a first undoped base layer is grown over the first wafer. After growing the first undoped base layer, the first wafer is transferred from the undoped epi chamber into a separate doped epi chamber. A first doped base layer is then grown over the first undoped based layer in the doped epi chamber. While the first wafer is being processed in the doped epi chamber, a second wafer can be processed in the undoped epi chamber. Another embodiment is a structure produced by the disclosed method and yet another embodiment comprises a transfer chamber, a transfer arm, a bake chamber, and a separate undoped epi chamber and a doped epi chamber for practicing the disclosed method.
1. A structure comprising:
a collector;
an undoped base layer situated over said collector, said undoped base layer grown in an undoped epi chamber;
a doped base layer situated over said undoped base layer, said doped base layer grown in a doped epi chamber;
wherein said undoped epi chamber prevents said undoped base layer from being contaminated by residual dopant material.
2. The structure of claim 1 wherein said undoped base layer comprises silicon-germanium.
3. The structure of claim 1 wherein said doped base layer comprises silicon-germanium doped with a dopant.
4. The structure of claim 3 wherein said dopant is boron.
5. The structure of claim 1 further comprising an emitter situated over said doped base layer.
6. The structure of claim 1 wherein said undoped base layer and said doped base layer are grown using a chemical vapor deposition process.
7. A structure comprising:
a collector;
a base comprising an undoped base layer and a doped base layer;
said undoped base layer situated over said collector, said undoped base layer grown in an undoped epi chamber;
said doped base layer situated over said undoped base layer, said doped base layer grown in a doped epi chamber;
wherein said undoped base layer comprises silicon-germanium;
wherein said undoped epi chamber prevents said undoped base layer from being contaminated by residual dopant material.
8. The structure of claim 7 wherein said doped base layer comprises silicon-germanium doped with a dopant.
9. The structure of claim 8 wherein said dopant is boron.
10. The structure of claim 7 wherein said base comprises carbon.
11. The structure of claim 7 further comprising an emitter situated over said doped base layer.
12. The structure of claim 11 wherein said emitter, said base, and said collector form a heterojunction bipolar transistor.
13. The structure of claim 7 wherein said undoped base layer and said doped base layer are grown using a chemical vapor deposition process.