Semiconductor device having localized extremely thin silicon on insulator channel region
A method of forming a transistor device includes forming a dummy gate stack structure over an SOI starting substrate, comprising a bulk layer, a global BOX layer over the bulk layer, and an SOI layer over the global BOX layer. Self-aligned trenches are formed completely through portions of the SOI layer and the global BOX layer at source and drain regions. Silicon is epitaxially regrown in the source and drain regions, with a local BOX layer re-established in the epitaxially regrown silicon, adjacent to the global BOX layer. A top surface of the local BOX layer is below a top surface of the global BOX layer. Embedded source and drain stressors are formed in the source and drain regions, adjacent a channel region. Silicide contacts are formed on the source and drain regions. The dummy gate stack structure is removed, and a final gate stack structure is formed.
1. A method of forming a transistor device, the method comprising:
forming a dummy gate stack structure over a silicon-on-insulator (SOI) starting substrate, the SOI starting substrate comprising a bulk layer, a global BOX layer over the bulk layer, and an SOI layer over the global BOX layer, the SOI layer having an initial thickness;
forming self-aligned trenches completely through portions of the SOI layer and the global BOX layer at locations corresponding to source and drain regions;
epitaxially regrowing silicon in the source and drain regions;
re-establishing, by oxygen ion implantation, a local BOX layer in the epitaxially regrown silicon, adjacent to the global BOX layer, wherein a top surface of the local BOX layer is below a top surface of the global BOX layer, and wherein a bottom surface of the local BOX layer is above a bottom surface of the global BOX layer;
forming embedded source and drain stressors in the source and drain regions, adjacent a portion of the SOI layer corresponding to a channel region;
forming silicide contacts on the source and drain regions;
removing the dummy gate stack structure; and
forming a final gate stack structure.
2. The method of claim 1 , wherein forming the silicide contacts results in forming silicide on the dummy gate stack structure prior to removal thereof.
3. The method of claim 2 , wherein the dummy gate stack structure comprises a dummy oxide, a dummy polysilicon on the dummy oxide, a poly screen oxide on the dummy polysilicon, and a nitride on the poly screen oxide, wherein the nitride and poly screen oxide are removed prior to forming the silicide contacts.
4. The method of claim 1 , further comprising preventing forming silicide on the dummy gate stack structure.
5. The method of claim 4 , wherein the dummy gate stack structure comprises a dummy oxide, a dummy polysilicon on the dummy oxide, a poly oxide cap on the dummy polysilicon, and a nitride on the poly oxide cap, and wherein the poly oxide cap is formed at an initial thickness sufficient so as to remain on the dummy polysilicon prior to forming the silicide contacts.
6. The method of claim 1 , further comprising thinning the SOI layer from the original thickness to a final thickness following the removal of the dummy gate stack structure and prior to forming the final gate stack structure.
7. The method of claim 6 , wherein the original thickness of the SOI layer corresponds to an ultra thin SOI (UTSOI) layer having a thickness range on the order of about 10 nanometers (nm) to about 30 nm.
8. The method of claim 7 , wherein the final thickness of the SOI layer corresponds to an extremely thin SOI (ETSOI) layer having a thickness range on the order of about 2 nm to about 10 nm.
9. The method of claim 1 , wherein the transistor device is an n-type field effect transistor (NFET) and the embedded source and drain stressors are selected to provide a tensile stress on the channel region.
10. The method of claim 1 , wherein the transistor device is a p-type field effect transistor (PFET) and the embedded source and drain stressors are selected to provide a compressive stress on the channel region.
11. A method of forming a transistor device, the method comprising:
forming a dummy gate stack structure over a silicon-on-insulator (SOI) starting substrate, the SOI starting substrate comprising a bulk layer, a global BOX layer over the bulk layer, and an SOI layer over the global BOX layer, the SOI layer having an initial thickness;
forming disposable spacers on sidewalls of the dummy gate stack structure;
forming self-aligned trenches completely through portions of the SOI layer and the global BOX layer at locations corresponding to source and drain regions;
epitaxially regrowing silicon in the source and drain regions;
re-establishing a local BOX layer in the epitaxially regrown silicon, adjacent to the global BOX layer, wherein a top surface of the local BOX layer is below a top surface of the global BOX layer;
forming embedded source and drain stressors in the source and drain regions, adjacent a portion of the SOI layer corresponding to a channel region;
performing, with the disposable spacers in place, a first dopant implant to establish lightly doped source/drain regions;
removing the disposable spacers and performing a second dopant implant to form source/drain extension regions;
forming final sidewall spacers and performing a third dopant implant to establish deep source/drain regions, and annealing to drive the implanted dopant materials;
forming silicide contacts on the source/drain regions;
removing the dummy gate stack structure;
thinning the SOI layer from the original thickness to a final thickness; and
forming a final gate stack structure.
12. The method of claim 11 , wherein forming the silicide contacts results in forming silicide on the dummy gate stack structure prior to removal thereof.
13. The method of claim 12 , wherein the dummy gate stack structure comprises a dummy oxide, a dummy polysilicon on the dummy oxide, a poly screen oxide on the dummy polysilicon, and a nitride on the poly screen oxide, wherein the nitride and poly screen oxide are removed prior to forming the silicide contacts.
14. The method of claim 11 , further comprising preventing forming silicide on the dummy gate stack structure.
15. The method of claim 14 , wherein the dummy gate stack structure comprises a dummy oxide, a dummy polysilicon on the dummy oxide, a poly oxide cap on the dummy polysilicon, and a nitride on the poly oxide cap, and wherein the poly oxide cap is formed at an initial thickness sufficient so as to remain on the dummy polysilicon prior to forming the silicide contacts.
16. The method of claim 11 , further comprising thinning the SOI layer from the original thickness to a final thickness following the removal of the dummy gate stack structure and prior to forming the final gate stack structure.
17. The method of claim 11 , wherein the final gate stack structure comprises a high-k, metal gate stack structure.
18. The method of claim 17 , wherein the final thickness of the SOI layer corresponds to an extremely thin SOI (ETSOI) layer having a thickness range on the order of about 2 nm to about 10 nm.
19. The method of claim 11 , wherein the transistor device is an n-type field effect transistor (NFET) and the embedded source and drain stressors are selected to provide a tensile stress on the channel region.
20. The method of claim 11 , wherein the transistor device is a p-type field effect transistor (PFET) and the embedded source and drain stressors are selected to provide a compressive stress on the channel region.