Metal gate structure and manufacturing method thereof
An NMOS transistor gate structure includes at least one spacer defining a gate region over a semiconductor substrate, a gate dielectric layer disposed on the gate region and lining an inner sidewall of the spacer, a bottom barrier layer conformally disposed on the gate dielectric layer, a work function metal layer disposed on the bottom barrier layer, and a filling metal partially wrapped by the work function metal layer. The bottom barrier layer has an oxygen concentration higher than a nitrogen concentration. The bottom barrier layer is in direct contact with the gate dielectric layer. The bottom barrier layer includes a material selected from Ta, TaN, TaTi, TaTiN and a combination thereof.
1. A method of manufacturing NMOS gate structure, comprising:
forming at least one dummy gate stack;
forming an inter-layer dielectric (ILD) layer around the dummy gate stack;
removing the dummy gate stack to form at least one recess;
forming a gate dielectric layer on a bottom surface and sidewalls of the recess;
forming a bottom barrier layer on the gate dielectric layer;
oxidizing a portion of the bottom barrier layer, wherein the oxidized portion of the bottom barrier layer has a nitrogen concentration and an oxygen concentration higher than the remaining portion of the bottom barrier layer;
forming a work function metal layer on the bottom barrier layer; and
filling a remaining portion of the recess with a filling metal.
2. The method of claim 1 , wherein before oxidizing the portion of the bottom barrier layer comprises:
depositing a mask layer on the bottom barrier layer; and
patterning the mask layer to expose the portion of the bottom barrier layer.
3. The method of claim 1 , wherein oxidizing the portion of the bottom barrier layer comprises:
treating the bottom barrier layer with a chemical solution containing an oxidizing agent and ammonium ions.
4. The method of claim 3 , wherein the oxidizing agent comprises H 2 O 2 .
5. The method of claim 3 , wherein the oxidizing agent comprises an acid with ClO 3 − , ClO − , or NO 3 − .
6. The method of claim 1 , wherein oxidizing the portion of the bottom barrier layer comprises:
exposing the bottom barrier layer to ozonated deionized water; and
treating the bottom barrier layer with a chemical solution containing ammonium ions.
7. The method of claim 1 , wherein the bottom barrier layer includes a material selected from Ta, TaN, TaTi, TaTiN and a combination thereof.
8. The method of claim 1 , wherein the oxygen concentration is higher than the nitrogen concentration at the portion of the bottom barrier layer.
9. A method of manufacturing metal gate structure, the method comprising:
forming a gate dielectric layer;
forming a bottom barrier layer on the gate dielectric layer;
oxidizing a portion of the bottom barrier layer, wherein the oxidized portion of the bottom barrier layer has a nitrogen concentration and an oxygen concentration higher than a nitrogen concentration and an oxygen concentration in the remaining portion of the bottom barrier layer; and;
forming a metal layer on the bottom barrier layer.
10. The method of claim 9 , wherein before oxidizing the portion of the bottom barrier layer comprises:
depositing a mask layer on the bottom barrier layer; and
patterning the mask layer to expose the portion of the bottom barrier layer.
11. The method of claim 9 , wherein oxidizing the portion of the bottom barrier layer comprises:
treating the bottom barrier layer with a chemical solution containing an oxidizing agent and ammonium ions.
12. The method of claim 11 , wherein the oxidizing agent comprises H 2 O 2 .
13. The method of claim 11 , wherein the oxidizing agent comprises an acid with ClO 3 − , ClO − , or NO 3 − .
14. The method of claim 9 , wherein oxidizing the portion of the bottom barrier layer comprises:
exposing the bottom barrier layer to ozonated deionized water; and
treating the bottom barrier layer with a chemical solution containing ammonium ions.
15. The method of claim 9 , wherein oxidizing the portion of the bottom barrier layer comprises:
exposing the bottom barrier layer to oxygen plasma; and
treating the bottom barrier layer with a chemical solution containing ammonium ions.
16. A method, comprising:
forming a gate dielectric layer over a substrate;
forming a tantalum-containing layer over the gate dielectric layer;
treating a portion of the tantalum-containing layer with oxygen to form a Ta—O dipole-containing layer, wherein the treated portion of the tantalum-containing layer has a nitrogen concentration and an oxygen concentration higher than a nitrogen concentration and an oxygen concentration in an untreated portion of the tantalum-containing layer; and
forming a metal layer over the Ta—O dipole-containing layer.
17. The method of claim 16 , wherein the treating the tantalum-containing layer with the oxygen is performed using a chemical solution containing oxidizing agent.
18. The method of claim 16 , wherein the treating the tantalum-containing layer with the oxygen is performed using a plasma containing oxygen.
19. The method of claim 16 , further comprising treating the tantalum-containing layer with nitrogen.
20. The method of claim 19 , wherein the treating the tantalum-containing layer with the nitrogen is performed using a chemical solution containing ammonium ions.