Method for reducing contact resistance in semiconductor structures
Semiconductor structures and methods reduce contact resistance, while retaining cost effectiveness for integration into the process flow by introducing a heavily-doped contact layer disposed between two adjacent layers. The heavily-doped contact layer may be formed through a solid-phase epitaxial regrowth method. The contact resistance may be tuned by adjusting dopant concentration and contact area configuration of the heavily-doped epitaxial contact layer.
1. A method, comprising:
forming a fin over a substrate;
forming a gate structure on the fin;
forming an epitaxial layer over a source/drain (S/D) region of the fin adjacent to the gate structure;
depositing a layer of doped amorphous material over the epitaxial layer; and
crystallizing a portion of the layer of doped amorphous material to form a region of crystallized material over the epitaxial layer.
2. The method of claim 1 , wherein the substrate is a bulk silicon wafer.
3. The method of claim 1 , wherein forming the gate structure comprises:
forming a gate dielectric on the fin; and
forming a gate electrode over the gate dielectric.
4. The method of claim 1 , further comprising forming a sidewall spacer adjacent to a sidewall of the gate structure, wherein the sidewall spacer comprises a spacer material in contact with at least a portion of the gate structure.
5. The method of claim 1 , further comprising doping the S/D region by implanting at least one dopant species into the fin.
6. The method of claim 1 , wherein forming the epitaxial layer comprises forming a recess in the fin and epitaxially growing a material in the recess.
7. The method of claim 1 , wherein depositing the layer of doped amorphous material comprises depositing a layer of n-doped amorphous silicon with a doping concentration in a range of about 5×10 20 atoms/cm 3 to about 7×10 21 atoms/cm 3 .
8. The method of claim 1 , wherein depositing the layer of doped amorphous material comprises depositing a layer of n-doped amorphous silicon germanium with a doping concentration in the range of about 5×10 20 atoms/cm 3 to about 7×10 21 atoms/cm 3 .
9. The method of claim 7 , wherein crystallizing the portion of the layer of doped amorphous silicon comprises performing a solid phase epitaxial regrowth at a temperature of about 600° C.
10. The method of claim 9 , further comprising removing the doped amorphous silicon after the solid phase epitaxial regrowth.
11. The method of claim 8 , wherein crystallizing the portion of the layer of doped amorphous silicon germanium comprises performing a solid phase epitaxial regrowth at a temperature of about 500° C.
12. The method of claim 11 , further comprising removing the doped amorphous silicon germanium after the solid phase epitaxial regrowth.
13. The method of claim 1 further comprising:
depositing a metal silicide on the region of crystallized material; and
forming a contact plug over the metal silicide.
14. The method of claim 1 , wherein the region of crystallized material comprises a doping concentration higher than a doping concentration of the epitaxial layer.
15. A method, comprising:
forming a fin over a substrate;
forming, on the fin, a gate structure with a sidewall;
forming a sidewall spacer adjacent to the sidewall;
doping a source/drain (S/D) region in the fin adjacent to the sidewall spacer;
forming an epitaxial layer over the S/D region adjacent to the sidewall spacer;
etching a portion of the epitaxial layer to expose a portion of fin sidewall;
depositing a layer of doped amorphous material over the gate structure, the sidewall spacer, the epitaxial layer, and the exposed portion of fin sidewall; and
crystallizing a portion of the layer of doped amorphous material to form a region of crystallized material over the epitaxial layer and the exposed portion of fin sidewall.
16. The method of claim 15 , wherein the region of crystallized material comprises a doping concentration higher than a doping concentration of the epitaxial layer.
17. The method of claim 15 , wherein depositing the layer of doped amorphous material comprises depositing a layer of n-doped amorphous material with a doping concentration in the range of about 5×10 20 atoms/cm 3 to about 7×10 21 atoms/cm 3 .
18. The method of claim 15 , wherein crystallizing the portion of the layer of doped amorphous material comprises performing a solid phase epitaxial regrowth.
19. The method of claim 18 , further comprising removing the doped amorphous material after the solid phase epitaxial regrowth.
20. A method, comprising:
forming a fin over a substrate;
forming, over the fin, a first gate structure with a first sidewall and a first sidewall spacer;
forming, over the fin, a second gate structure with a second sidewall and a second sidewall spacer, the second sidewall spacer opposing the first sidewall spacer;
doping a source/drain (S/D) region in the fin between the first sidewall spacer and the second sidewall spacer;
forming an epitaxial layer over the S/D region;
etching a portion of the epitaxial layer to expose a portion of fin sidewall;
depositing a layer of doped amorphous material over the first and second gate structures, the first and second sidewall spacers, the epitaxial layer and the exposed portion of fin sidewall; and
crystallizing a portion of the layer of doped amorphous material to form a region of crystallized material over the epitaxial layer and the exposed portion of fin sidewall, wherein the region of crystallized material comprises a doping concentration higher than a doping concentration of the epitaxial layer.