Silicon germanium-on-insulator formation by thermal mixing
A layer of amorphous silicon is formed on a germanium-on-insulator substrate, or a layer of germanium is formed on a silicon-on-insulator substrate. An anneal is then performed which causes thermal mixing of silicon and germanium atoms within one of the aforementioned structures and subsequent formation of a silicon germanium-on-insulator material.
1. A method of forming a semiconductor structure, said method comprising:
forming an amorphous silicon layer portion directly on a topmost surface of an active silicon germanium (SiGe) region of a silicon germanium-on-insulator material;
forming a gate structure on a topmost surface of said amorphous silicon layer portion, wherein said gate structure comprises a gate dielectric portion present directly on the topmost surface of said amorphous silicon layer portion and a gate conductor portion present on said dielectric portion;
forming a gate dielectric spacer on sidewalls of said gate structure and sidewalls of said amorphous silicon layer portion, wherein a bottommost surface of said gate dielectric spacer is in direct contact with said topmost surface of said active SiGe region and is coplanar with a bottommost surface of said amorphous silicon layer portion; and
forming an embedded SiGe channel region in said active SiGe region directly beneath said gate structure utilizing a thermal mixing process in which silicon atoms from said amorphous silicon layer portion intermix with germanium atoms in said SiGe active region to form said embedded SiGe channel region, wherein said thermal mixing process entirely removes the amorphous silicon layer from the semiconductor structure such that a topmost surface of said embedded SiGe channel region is in direct physical contact with a bottommost surface of said gate dielectric portion and said embedded SiGe channel region has a lower germanium content than said active SiGe region.
2. The method of claim 1 , wherein said amorphous silicon layer portion is present on a portion of said active silicon germanium region.
3. The method of claim 1 , wherein said amorphous silicon layer portion comprises hydrogenated amorphous silicon.
4. The method of claim 1 , wherein said active silicon germanium region is a fin structure or a nanowire structure.
5. The method of claim 1 , wherein a dielectric structure is located on each side of the active silicon germanium region.
6. The method of claim 1 , wherein said gate structure has sidewalls that are vertically aligned to sidewalls of said amorphous silicon layer portion.
7. The method of claim 1 , wherein said gate structure is a sacrificial gate structure, and said sacrificial gate structure is replaced with a functional gate structure after forming said embedded SiGe channel region.
8. The method of claim 1 , wherein said gate structure is a functional gate structure, and wherein said gate dielectric material portion of said functional gate structure has a bottommost surface that directly contacts a topmost surface of said amorphous silicon layer prior to said forming said embedded SiGe channel region.
9. The method of claim 1 , wherein sidewalls of said embedded SiGe channel region are vertically aligned with sidewalls of said gate structure.
10. The method of claim 1 , wherein said embedded SiGe channel region is compressively strained.
11. The method of claim 1 , wherein said silicon germanium-on-insulator material is formed by a process comprising:
providing a structure comprising, from bottom to top, a germanium-on-insulator substrate and an amorphous silicon layer, wherein said germanium-on-insulator substrate comprises a germanium layer in direct contact with an insulator; and
converting said structure into a silicon germanium-on-insulator material by annealing, wherein during said annealing silicon atoms from said amorphous silicon layer intermix with germanium atoms in a germanium layer of said germanium-on-insulator substrate to form a silicon germanium layer.
12. The method of claim 1 , wherein said silicon germanium-on-insulator material is formed by a process comprising:
providing a structure comprising, from bottom to top, a silicon-on-insulator substrate and a germanium silicon layer; and
converting said structure into a silicon germanium-on-insulator material by annealing, wherein during said annealing silicon atoms from a silicon layer of the silicon-on-insulator substrate with germanium atoms in said germanium layer to form a silicon germanium layer directly on an insulator of said silicon-on-insulator substrate.