Method and device for self-aligned contact on a non-recessed metal gate
A methodology for forming a self-aligned contact (SAC) that exhibits reduced likelihood of a contact-to-gate short circuit failure and the resulting device are disclosed. Embodiments may include forming a replacement metal gate, with spacers at opposite sides thereof, on a substrate, forming a recess in an upper surface of the spacers along outer edges of the replacement metal gate, and forming an aluminum nitride (AlN) cap over the metal gate and in the recess.
1. A method comprising:
forming a replacement metal gate, with spacers at opposite sides thereof and a barrier layer adjacent the spacers, on a substrate;
forming a recess that penetrates an upper surface of the spacers, between an outer edge of the spacers and the barrier layer, and along outer edges of the replacement metal gate; and
forming an aluminum nitride (AlN) cap over the metal gate and in the recess between the spacers and barrier layer.
2. The method according to claim 1 , wherein the recess is formed to a depth of 3 nanometers (nm) to 10 nm.
3. The method according to claim 1 , comprising forming the recess by a dry or wet etch process.
4. The method according to claim 1 , wherein the nitride cap is formed to a uniform thickness of 1 nm to 10 nm above an upper surface of the metal gate.
5. The method according to claim 1 , comprising forming the AlN cap by:
forming an aluminum (Al) cap over the metal gate and in the recess; and
converting the Al to AlN.
6. The method according to claim 5 , comprising forming the Al cap by a selective growth process.
7. The method according to claim 6 , comprising converting the Al cap to AlN by a nitrogen plasma treatment or a nitrogen plasma doping process.
8. The method according to claim 7 , comprising converting the Al cap to AlN at a process temperature less than 400 degrees Celsius (° C.).
9. The method according to claim 1 , further comprising:
forming an oxide layer to cover the metal gate and AlN cap to a uniform height above the substrate; and
forming a self-aligned contact (SAC) through the oxide layer.
10. A device comprising:
a replacement metal gate, with spacers at opposite sides thereof, on a substrate;
a recess that penetrates an upper surface of the spacers along outer edges of the replacement metal gate; and
an aluminum nitride (AlN) cap over the metal gate and in the recess between the spacers and a barrier layer,
wherein the metal gate comprises the barrier layer adjacent the spacers, and
the recess is formed between an outer edge of the spacers and the barrier layer.
11. The device according to claim 10 , wherein the recess has a depth of 3 nanometers (nm) to 10 nm.
12. The device according to claim 10 , wherein the AlN cap has a uniform thickness of 1 nm to 10 nm above an upper surface of the metal gate.
13. The device according to claim 10 , further comprising:
an oxide layer covering the metal gate and AlN cap to a uniform height above a substrate; and
a self-aligned contact (SAC) through the oxide layer.
14. The device according to claim 13 , wherein the SAC partially overlaps the AlN cap.
15. The device according to claim 10 , wherein:
the barrier layer comprises titanium nitride (TiN).
16. A method comprising:
forming a replacement metal gate, with spacers at opposite sides thereof and a barrier layer adjacent the spacers, on a substrate;
forming a recess that penetrates an upper surface of the spacers, between an outer edge of the spacers and the barrier layer, and along outer edges of the replacement metal gate;
forming an aluminum nitride (AlN) cap over the metal gate and in the recess by:
forming an aluminum (Al) cap over the metal gate and in the recess between the spacers and barrier layer by a selective growth process, and
converting the Al to AlN;
forming an oxide layer to cover the metal gate and AlN cap to a uniform height above the substrate; and
forming a self-aligned contact (SAC) through the oxide layer partially overlapping the AlN cap.
17. The method according to claim 16 , comprising forming the recess by a dry or wet etch process.
18. The method according to claim 17 , comprising:
forming the recess to a depth of 3 nanometers (nm) to 10 nm; and
forming the nitride cap to a uniform thickness of 1 nm to 10 nm above an upper surface of the metal gate.
19. The method according to claim 16 , comprising converting the Al cap to AlN by a nitrogen plasma treatment or a nitrogen plasma doping process at a process temperature less than 400 degrees Celsius (° C.).
20. The method according to claim 16 , comprising forming the SAC by reactive ion etching (RIE) a contact hole and filling the contact hole with a contact metal.