Asymmetric high-k dielectric for reducing gate induced drain leakage
An asymmetric high-k dielectric for reduced gate induced drain leakage in high-k MOSFETs and methods of manufacture are disclosed. The method includes performing an implant process on a high-k dielectric sidewall of a gate structure. The method further includes performing an oxygen annealing process to grow an oxide region on a drain side of the gate structure, while inhibiting oxide growth on a source side of the gate structure adjacent to a source region.
1. A method comprising:
providing a semiconductor fin having a dummy gate covering a channel region of the semiconductor fin and defining source and drain sides of the channel region of the semiconductor fin;
forming an interlevel dielectric overlying the dummy gate;
removing the dummy gate leaving a trench over the channel region of the semiconductor fin;
forming an interfacial layer on the channel region of the semiconductor fin;
forming a high-k dielectric layer on the interfacial layer and on exposed sides of the trench; and
selectively oxidizing the drain side of the channel region of the semiconductor fin, to produce an asymmetric interfacial layer that is thicker on drain side of the channel region of the semiconductor fin.
2. The method of claim 1 , wherein the asymmetric interfacial layer comprises oxide.
3. The method of claim 1 , wherein the asymmetric interfacial layer further comprises nitrogen.
4. The method of claim 1 , wherein the interfacial layer is formed prior to forming the dummy gate and remains after the dummy gate is removed.
5. The method of claim 1 , wherein the interfacial layer is formed after the dummy gate is removed.
6. The method of claim 1 , wherein selectively oxidizing the drain side of the channel region of the semiconductor fin comprises performing an anneal process.
7. The method of claim 6 , wherein the anneal process takes place after the trench has been filled with conductive material.
8. The method of claim 6 , wherein the anneal process is an oxygen anneal.
9. The method of claim 8 , wherein the oxygen anneal is performed at about 500° C.
10. The method of claim 1 , wherein the asymmetric interfacial layer on the drain side of the channel region of the semiconductor fin is approximately 1.8 nm.
11. The method of claim 1 , wherein the asymmetric interfacial layer on the drain side of the channel region of the semiconductor fin is approximately 0.3 nm thicker than the asymmetric interfacial layer on the source side of the channel region of the semiconductor fin.
12. The method of claim 1 , wherein selectively oxidizing the drain side of the channel region of the semiconductor fin comprises performing an angled implant into the high-k dielectric layer on a source-side trench sidewall followed by an oxidation process.
13. The method of claim 12 , wherein an implanted species blocks diffusion of oxygen through implanted portions of the high-k dielectric layer.
14. The method of claim 13 , wherein the implanted species is nitrogen.
15. The method of claim 12 , wherein an implanted species damages implanted portions of the high-k dielectric layer.
16. The method of claim 15 , further comprising etching implanted portions of the high-k dielectric layer and then filling the trench with a conductive material prior to the oxidation process.
17. The method of claim 1 , further comprising etching part of the high-k dielectric layer on a source-side trench sidewall prior to selectively oxidizing the drain side of the channel region of the semiconductor fin.
18. The method of claim 17 wherein the etching comprises using a dilute hydrofluoric acid (HF) process.
19. The method of claim 17 , further comprising filling the trench with conductive material after etching part of the high-k dielectric layer and prior to selectively oxidizing the drain side of the channel region of the semiconductor fin.
20. The method of claim 1 , further comprising filling the trench with conductive material to form a gate structure, wherein selectively oxidizing the drain side of the channel region of the semiconductor fin comprises using a mask to block diffusion of oxygen through the high-k dielectric layer on a source-side trench sidewall.