Contacts to semiconductor substrate and methods of forming same

1. A method for forming a contact in a dielectric layer to a semiconductor substrate, the method comprising:

forming a contact opening in the dielectric layer over the semiconductor substrate to expose an upper portion of the semiconductor substrate;

depositing a first liner layer to conformally coat the contact opening

causing a portion of the first liner layer to diffuse into the upper portion of the semiconductor substrate to form a first intermix region at the upper portion of the semiconductor substrate;

depositing a refractory metal layer over the first intermix region; and

depositing a metal in the contact opening thereby forming the contact.

2. The method of claim 1 , further comprising:

removing a remaining non-diffused portion of the first liner layer to expose the first intermix region at the upper portion of the semiconductor substrate prior to depositing the refractory metal layer.

3. The method of claim 1 , wherein the depositing the first liner layer includes depositing at least one of: nickel platinum (NiPt), nickel (Ni), titanium (Ti), titanium silicide (TiSi), cobalt (Co), erbium (Er), platinum (Pt), and ytterbium (Yb).

4. The method of claim 1 , wherein depositing the refractory metal layer includes depositing a bilayer of titanium (Ti) and titanium nitride (TiN).

5. The method of claim 1 , wherein depositing the first liner layer includes performing physical vapor deposition.

6. The method of claim 1 , further comprising:

polishing the metal; and

performing a laser anneal of the opening such that a second intermix region is formed at the upper portion of the semiconductor substrate and a bottom surface of the contact, wherein the second intermix region is composed of materials of the first intermix region and a material used for the refractory metal layer.

7. The method of claim 1 , wherein the depositing the first liner layer includes depositing nickel platinum (NiPt), the depositing the refractory metal layer includes depositing a bilayer of titanium (Ti) and titanium nitride (TiN), and the depositing the metal in the opening includes depositing tungsten (W).

8. A method for forming a set of contacts in a dielectric layer to a field effect transistor, the field effect transistor including a source, a drain, and a gate between the source and the drain, the method comprising:

forming a contact opening in the dielectric layer to expose an upper-portion of each of the source and the drain;

depositing a first liner layer to conformally coat each contact opening and causing a portion of the first liner layer to diffuse into the upper portion of each of the source and the drain to form a first intermix region at the upper portion of the each of the source and the drain;

depositing a refractory metal layer over the first intermix region; and

depositing a metal to substantially coat the refractory metal layer and substantially fill each of the openings thereby forming the set of contacts.

9. The method of claim 8 , further comprising:

removing a remaining non-diffused portion of the first liner layer to expose the intermix region prior to depositing the refractory metal layer.

10. The method of claim 8 , wherein the depositing the first liner layer includes depositing nickel platinum (NiPt), nickel (Ni), titanium (Ti), titanium silicide (TiSi), cobalt (Co), erbium (Er), platinum (Pt), and ytterbium (Yb).

11. The method of claim 8 , wherein the depositing the refractory metal layer includes depositing a bilayer of titanium (Ti) and titanium nitride (TiN).

12. The method of claim 8 , wherein the depositing the first liner layer includes performing physical vapor deposition.

13. The method of claim 8 , further comprising:

polishing the metal in each of the openings; and

performing a laser anneal of each of the openings such that a second intermix region is formed at the upper portion of the respective source and drain thereunder, wherein the second intermix region is composed of materials of the first intermix region and a material used for the refractory metal layer.

14. The method of claim 13 , wherein the depositing the first liner layer includes depositing nickel platinum (NiPt), the depositing the refractory metal layer includes depositing a bilayer of titanium (Ti) and titanium nitride (TiN), and the depositing the metal in the opening includes depositing tungsten (W).