Doping for semiconductor device with conductive feature
The present disclosure relates generally to doping for conductive features in a semiconductor device. In an example, a structure includes an active region of a transistor. The active region includes a source/drain region, and the source/drain region is defined at least in part by a first dopant having a first dopant concentration. The source/drain region further includes a second dopant with a concentration profile having a consistent concentration from a surface of the source/drain region into a depth of the source/drain region. The consistent concentration is greater than the first dopant concentration. The structure further includes a conductive feature contacting the source/drain region at the surface of the source/drain region.
1. A method comprising:
defining an active area on a substrate, the active area including a source/drain region, the source/drain region being defined at least in part by a first dopant having a first concentration;
implanting a second dopant into the source/drain region, the second dopant having a consistent concentration extending from a surface of the source/drain region to a depth in the source/drain region, the consistent concentration being greater than the first concentration, wherein implanting the second dopant into the source/drain region amorphizes at least a portion of the source/drain region; and
forming a conductive feature contacting the source/drain region.
2. The method of claim 1 , wherein the source/drain region comprises a germanium-containing material, and the second dopant comprises a gallium-containing species.
3. The method of claim 1 further comprising amorphizing at least a portion of the source/drain region comprising implanting an amorphizing impurity into the source/drain region before implanting the second dopant.
4. The method of claim 1 , wherein the depth is at least 15 nm.
5. The method of claim 1 , wherein the depth is at least 10 nm.
6. The method of claim 1 , wherein defining the active area on the substrate comprises defining the source/drain region in the active area, wherein defining the source/drain region comprises epitaxially growing the source/drain region.
7. The method of claim 6 , wherein epitaxially growing the source/drain region comprises in situ doping the source/drain region with the first dopant.
8. The method of claim 1 , wherein implanting the second dopant is performed using an implant energy in a range from about 1 keV to about 15 keV, with a dosage concentration in a range from about 5×10 13 cm −2 to about 5×10 14 cm −2 .
9. A method comprising:
forming a first source/drain region in a semiconductor region;
forming a platform dopant region in the first source/drain region, wherein a first concentration of a first dopant in the platform dopant region is constant from an upper surface of the semiconductor region to a first depth;
forming a tailing dopant region in the first source/drain region, wherein a second concentration of the first dopant in the tailing dopant region decreases as the tailing dopant region extends away from the platform dopant region; and
forming a contact to the platform dopant region.
10. The method of claim 9 , wherein the first dopant comprises gallium.
11. The method of claim 9 , further comprising amorphizing at least a portion of the first source/drain region prior to forming the platform dopant region.
12. The method of claim 11 , wherein the amorphizing is performed at least in part by implanting a second dopant, wherein the first dopant is different than the second dopant.
13. The method of claim 9 , wherein the first depth is about 8 nm.
14. The method of claim 13 , wherein the first depth is about 12 nm.
15. A method comprising:
forming a first source/drain region in a semiconductor region;
implanting a first dopant into the first source/drain region to form an amorphous region;
implanting a second dopant into the amorphous region, wherein the first dopant is different than the second dopant; and
recrystallizing the amorphous region, wherein after recrystallizing, the first source/drain region comprises a platform dopant region and a tailing dopant region, the platform dopant region having a consistent doping profile of the second dopant to a first depth, the tailing dopant region having a decreasing concentration as the tailing dopant region extends into the semiconductor region from the platform dopant region.
16. The method of claim 15 , wherein the semiconductor region comprises silicon germanium and the first dopant comprises germanium.
17. The method of claim 16 , wherein the second dopant comprises gallium.
18. The method of claim 15 , wherein the consistent doping profile has a consistent concentration greater than 1×10 21 cm −3 .
19. The method of claim 15 , further comprising:
forming a dielectric layer over the first source/drain region;
forming an opening in the dielectric layer, wherein the opening exposes the platform dopant region;
forming a first metal layer over the platform dopant region;
annealing to cause the first metal layer to react with the platform dopant region to form a silicide region; and
forming a second metal layer over the silicide region.
20. The method of claim 15 , wherein a depth of the tailing dopant region is at least 10 nm.