Dielectric isolated fin with improved fin profile
A method of forming a fin structure that includes forming a plurality of fin structures from a bulk semiconductor substrate and forming a dielectric spacer on a sidewall of each fin structure in the plurality of fin structure. A semiconductor spacer is formed on a sidewall of the dielectric spacer. A dielectric fill is formed in the space between the adjacent fin structures. The semiconductor spacer and a portion of the fin structures that is present below a lower surface of the dielectric spacer are oxidized. Oxidizing a base portion of the fin structures produces a first strain and oxidizing the semiconductor spacer produces a second strain that is opposite the first strain.
1. A method for forming a fin structure comprising:
forming a plurality of fin structures from a bulk semiconductor substrate;
forming dielectric spacers on a sidewall of the plurality of fin structures;
forming semiconductor spacers on a sidewall of the dielectric spacers;
etching an exposed portion of the bulk semiconductor substrate that is present between the semiconductor spacers on adjacent fin structures to form a pedestal portion of the bulk substrate;
forming a dielectric fill in a space between the adjacent fin structures; and
annealing the semiconductor spacer and a portion of the plurality of fin structures that is present below a lower surface of the dielectric spacers, wherein said annealing the portion of the plurality of fin structures produces a first strain and said annealing the semiconductor spacers produces a second strain that is opposite the first strain.
2. The method of claim 1 , wherein said annealing of the semiconductor spacers and the portion of the plurality of fin structures produces oxidized semiconductor spacers and an oxidized portion of the plurality of fin structures that is present below the lower surface of the dielectric spacers.
3. The method of claim 1 , wherein a magnitude of the second strain is substantially equal to a magnitude of the first strain so that the plurality of fin structures are in a substantially neutral strain state.
4. The method of claim 1 , wherein the forming of the semiconductor spacer comprises:
forming a conformal layer of a semiconductor material on the dielectric spacers, the plurality of fin structures and an upper surface of bulk substrate that is present between the adjacent fin structures in the plurality of fin structures; and
anisotropically etching the conformal layer of the semiconductor material to form the semiconductor spacer on the sidewall of the dielectric spacers.
5. The method of claim 1 , wherein the semiconductor spacers are comprised of an amorphous silicon containing material or a multi-crystalline silicon containing material.
6. The method of claim 1 , wherein the pedestal portion of the bulk substrate has a width greater than a width of a fin structure of said plurality of fin structures and the method further comprises etching the pedestal portion of the plurality of fin structures to reduce the width of the pedestal portion to be substantially equal to the width of the fin structure.
7. The method of claim 2 , wherein said annealing the portion of the plurality of fin structures that is present below the lower surface of the dielectric spacers comprises a thermal oxidation at a temperature ranging from 900° C. to 1300° C.
8. The method of claim 1 further comprising recessing the dielectric fill to expose the dielectric spacers and removing the dielectric spacers.
9. The method of claim 8 further comprising:
forming a gate structure on a portion of at least one of the plurality of fin structures;
forming a source region on said at least one of the plurality of fin structures on a first side of the gate structure; and
forming a drain region on said at least one of the plurality of fin structures on a second side of the gate structure.
10. A method for forming a fin structure comprising:
forming a plurality of fin structures from a bulk semiconductor substrate;
forming a first dielectric fill in a space between adjacent fin structures of the plurality of fin structures, wherein sidewalls of an upper portion of the plurality of fin structures are exposed;
forming dielectric spacers on the sidewalls of the plurality of fin structure that are exposed;
forming semiconductor spacers on a sidewall of the dielectric spacers;
forming a second dielectric fill in the space between the adjacent fin structures on the first dielectric fill; and
annealing the semiconductor spacers and a lower portion of the fin structures that is present below a lower surface of the dielectric spacers, wherein said annealing the portion of the fin structures produces a first strain and oxidizing the semiconductor spacers produces a second strain that is opposite the first strain.
11. The method of claim 10 , wherein said annealing of the semiconductor spacers and the portion of the plurality of fin structures that is present below the lower surface of the dielectric spacers produces an oxidized semiconductor spacers and an oxidized portion of the plurality of fin structures that is present below the lower surface of the dielectric spacers.
12. The method of claim 10 , wherein a magnitude of the second strain is substantially equal to a magnitude of the first strain so that the plurality of fin structures are in a substantially neutral strain state.
13. The method of claim 10 , wherein said forming the dielectric spacers comprises:
depositing a conformal dielectric layer on the plurality of fin structures and an upper surface of the first dielectric fill; and
anisotropically etching the conformal dielectric layer to form the dielectric spacers.
14. The method of claim 10 , wherein the semiconductor spacers are comprised of an amorphous silicon containing material or a multi-crystalline silicon containing material.
15. The method of claim 10 , wherein the forming of the semiconductor spacers comprises:
forming a conformal layer of a semiconductor material on the dielectric spacers, the plurality of fin structures and an upper surface of first dielectric fill that is present between the adjacent fin structures of the plurality of fin structures; and
anisotropically etching the conformal layer of the semiconductor material to form the semiconductor spacers on the sidewall of the dielectric spacers.
16. The method of claim 10 , wherein forming the second dielectric fill in the space between the adjacent fin structures comprises:
depositing the second dielectric fill on the first dielectric fill; and
planarizing the second dielectric fill until an upper surface of the plurality of fin structures is coplanar with an upper surface of the dielectric fill.
17. The method of claim 16 , wherein said oxidizing the portion of the plurality of fin structures that is present below the lower surface of the dielectric spacers comprises a thermal oxidation at a temperature ranging from 900° C. to 1300° C.
18. The method of claim 10 further comprising:
forming a gate structure on a portion of at least one of the plurality of fin structures;
forming a source region on said at least one of the plurality of fin structures on a first side of the gate structure; and
forming a drain region on said at least one of the plurality of fin structures on a second side of the gate structure.