Techniques for integration of Ge-rich p-MOS source/drain
Techniques are disclosed for improved integration of germanium (Ge)-rich p-MOS source/drain contacts to, for example, reduce contact resistance. The techniques include depositing the p-type Ge-rich layer directly on a silicon (Si) surface in the contact trench location, because Si surfaces are favorable for deposition of high quality conductive Ge-rich materials. In one example method, the Ge-rich layer is deposited on a surface of the Si substrate in the source/drain contact trench locations, after removing a sacrificial silicon germanium (SiGe) layer previously deposited in the source/drain locations. In another example method, the Ge-rich layer is deposited on a Si cladding layer in the contact trench locations, where the Si cladding layer is deposited on a functional p-type SiGe layer. In some cases, the Ge-rich layer comprises at least 50% Ge (and may contain tin (Sn) and/or Si) and is boron (B) doped at levels above 1E20 cm −3 .
1. An integrated circuit including at least one transistor, the integrated circuit comprising:
a gate structure;
a body at least below the gate structure;
a first region adjacent the body, the first region including a first layer, the first layer including germanium at a concentration of at least 50 atomic percent throughout the first layer, wherein the first layer is in direct contact with a surface that consists essentially of silicon; and
a second region adjacent the body, the second region including a second layer, the second layer including germanium at a concentration of at least 50 atomic percent throughout the second layer, wherein the second layer is in direct contact with the surface.
2. The integrated circuit of claim 1 , wherein the surface is a surface of a substrate.
3. The integrated circuit of claim 1 , wherein the surface is a surface of a cladding layer, the cladding layer on an additional layer, the additional layer including silicon, germanium, and p-type impurities.
4. The integrated circuit of claim 3 , wherein the additional layer includes germanium at a concentration of 30 to 70 atomic percent.
5. The integrated circuit of claim 1 , wherein the first and second layers include silicon.
6. The integrated circuit of claim 1 , wherein the first and second layers further include tin.
7. The integrated circuit of claim 6 , wherein the first and second layers include silicon.
8. The integrated circuit of claim 1 , wherein the first and second layers include boron.
9. The integrated circuit of claim 1 , wherein the surface is undoped such that it consists only of silicon.
10. The integrated circuit of claim 1 , further comprising an additional layer on the first and second layers, the additional layer including metal and germanium.
11. The integrated circuit of claim 1 , wherein the body includes germanium.
12. The integrated circuit of claim 1 , wherein the body is a fin, the fin between portions of the gate structure.
13. The integrated circuit of claim 1 , wherein the gate structure is around the body.
14. A computing system comprising the integrated circuit of claim 1 .
15. An integrated circuit including at least one transistor, the integrated circuit comprising:
a gate structure;
a body at least below the gate structure;
a first region adjacent the body, the first region including
a first portion including silicon and germanium,
a second portion on the first portion, the second portion consisting essentially of silicon, and
a third portion on the second portion, the third portion including germanium at a concentration of at least 50 atomic percent throughout the third portion; and
a second region adjacent the body, the second region including
a first portion including silicon and germanium,
a second portion on the first portion, the second portion consisting essentially of silicon, and
a third portion on the second portion, the third portion including germanium at a concentration of at least 50 atomic percent throughout the third portion.
16. The integrated circuit of claim 15 , wherein the third portion of the first and second regions includes silicon.
17. The integrated circuit of claim 15 , wherein the third portion of the first and second regions includes tin.
18. An integrated circuit including at least one transistor, the integrated circuit comprising:
a substrate essentially consisting of silicon;
a gate structure above a portion of the substrate;
a first region adjacent the portion of the substrate, the first region including germanium at a concentration of at least 50 atomic percent throughout the first region; and
a second region adjacent the portion of the substrate, the second region including germanium at a concentration of at least 50 atomic percent throughout the second region.
19. The integrated circuit of claim 18 , wherein the first and second regions include silicon.
20. The integrated circuit of claim 18 , wherein the first and second regions include tin.