Low thickness dependent work-function nMOS integration for metal gate
Film stacks and methods of forming film stacks including a high-k dielectric layer on a substrate, a high-k capping layer on the high-k dielectric layer, an n-metal layer on the high-k capping layer and an n-metal capping layer on the n-metal layer. The n-metal layer having an aluminum rich interface adjacent the high-k capping layer.
1. A film stack comprising:
a high-k dielectric layer on a substrate;
a high-k capping layer on the high-k dielectric layer;
an n-metal layer on the high-k capping layer, the n-metal layer having an aluminum rich interface adjacent the high-k capping layer between the high-k capping layer and the high-k dielectric layer, the n-metal layer comprises tantalum, silicon and aluminum; and
an n-metal capping layer on the n-metal layer,
wherein the aluminum migrates from the n-metal layer through the high-k capping layer.
2. The film stack of claim 1 , wherein the high-k dielectric layer comprises HfO 2 .
3. The film stack of claim 2 , wherein the high-k dielectric layer has a thickness in the range of about 10 Å to about 20 Å.
4. The film stack of claim 1 , wherein the high-k capping layer comprises titanium nitride.
5. The film stack of claim 4 , wherein the high-k capping layer has a thickness in the range of about 5 Å to about 20 Å.
6. The film stack of claim 1 , wherein the n-metal layer has a thickness in the range of about 10 Å to about 30 Å.
7. The film stack of claim 1 , wherein the n-metal capping layer comprises TiN.
8. The film stack of claim 7 , wherein the n-metal capping layer has a thickness in the range of about 10 Å to 60 Å.
9. The film stack of claim 1 , further comprising a silicon oxide layer below the high-k dielectric layer.
10. The film stack of claim 9 , wherein the silicon oxide layer has a thickness in the range of about 5 Å to about 10 Å.
11. The film stack of claim 1 , further comprising a metal layer comprising tungsten above the n-metal capping layer.
12. A method of forming a film stack, the method comprising:
forming a high-k dielectric layer on a substrate;
forming a high-k capping layer on the high-k dielectric layer;
forming an n-metal layer on the high-k capping layer, the n-metal layer having an aluminum rich interface adjacent the high-k capping layer between the high-k capping layer and the high-k dielectric layer, the n-metal layer comprising tantalum, silicon and aluminum; and
forming an n-metal capping layer on the n-metal layer,
wherein the aluminum migrates from the n-metal layer through the high-k capping layer.
13. The method of claim 12 , wherein the high-k dielectric layer comprises HfO 2 with a thickness in the range of about 10 Å to about 20 Å.
14. The method of claim 12 , wherein the high-k capping layer comprises titanium nitride with a thickness in the range of about 5 Å to about 20 Å.
15. The method of claim 12 , wherein the n-metal layer comprises tantalum, silicon and aluminum and has a thickness in the range of about 10 Å to about 30 Å.
16. The method of claim 12 , wherein the n-metal capping layer comprises TiN with a thickness in the range of about 10 Å to 60 Å.
17. The method of claim 12 , wherein the substrate comprises a silicon oxide with a thickness in the range of about 5 Å to about 10 Å before formation of the high-k dielectric layer and the method further comprises forming a metal layer comprising tungsten above the n-metal capping layer.