Self-aligned structure for bulk FinFET
View Patent ↗A FinFET structure which includes a bulk semiconductor substrate; semiconductor fins extending from the bulk semiconductor substrate, each of the semiconductor fins having a top portion and a bottom portion such that the bottom portion of the semiconductor fins is doped and the top portion of the semiconductor fins is undoped; a portion of the bulk semiconductor substrate directly underneath the plurality of semiconductor fins being doped to form an n+ or p+ well; and an oxide formed between the bottom portions of the fins. Also disclosed is a method for forming a FinFET device.
1. A method of forming a FinFET device comprising, in the following order:
forming a plurality of semiconductor fins from a bulk semiconductor substrate;
forming an oxide layer between each of the plurality of semiconductor fins, the oxide layer extending from the bulk semiconductor substrate only part way up a sidewall of each of the semiconductor fins to cover a bottom portion of each of the semiconductor fins, a top portion of the sidewall of each of the semiconductor fins being exposed and not covered by the oxide layer;
forming a dummy spacer on the exposed top portion of each of the semiconductor fins;
completely stripping the oxide layer to expose the bulk semiconductor substrate and the bottom portion of each of the semiconductor fins;
depositing a doping material to be in contact with the exposed bulk semiconductor substrate and the bottom portion of each of the semiconductor fins previously covered by the oxide layer;
heat treating the bulk semiconductor substrate to drive in dopants from the doping material into the exposed bulk semiconductor substrate and the bottom portion of each of the semiconductor fins;
stripping only the doping material;
forming a second oxide layer only in contact with the exposed bulk semiconductor substrate and the bottom portion of each of the semiconductor fins previously contacted by the doping material; and
stripping the dummy spacer from each of the semiconductor fins.
2. The method of claim 1 wherein depositing a doping material is by epitaxial deposition.
3. The method of claim 2 wherein the doping material is phosphorous-silicon.
4. The method of claim 2 wherein the doping material is boron-silicon germanium or boron-silicon.
5. The method of claim 1 wherein depositing a doping material is by plasma deposition.
6. The method of claim 5 wherein the doping material is phosphorous.
7. The method of claim 5 wherein the doping material is boron.
8. The method of claim 1 wherein between completely stripping the oxide layer and depositing a doping material, further comprising thinning the exposed bottom portion of each of the semiconductor fins.
9. The method of claim 1 wherein the semiconductor fins and bulk semiconductor substrate are silicon.
10. The method of claim 1 further comprising forming a gate that wraps around at least one of the semiconductor fins.