Formation of liner and barrier for tungsten as gate electrode and as contact plug to reduce resistance and enhance device performance

1. A method of forming a film stack on a substrate, comprising:

performing a silicon containing gas soak process to form a silicon containing layer over the substrate;

depositing a tungsten nitride layer on the silicon containing layer;

reacting the silicon containing layer with the tungsten nitride layer to form a tungsten silicide layer at an interface between the tungsten nitride layer and the silicon containing layer;

subjecting the tungsten nitride layer to a nitridation treatment using active nitrogen species from a remote plasma; and

depositing a conductive bulk layer directly on the tungsten nitride layer.

2. The method of claim 1 , wherein the silicon containing soak gas process comprises exposing the substrate to a silicon containing gas comprising SiH 4 , Si 2 H 6 or derivatives thereof.

3. The method of claim 2 , wherein the silicon containing gas soak process is performed at a temperature between about 200 degrees Celsius and about 800 degrees Celsius, and at a pressure between about 0.05 Torr to about 500 Torr.

4. The method of claim 3 , wherein a flow rate of the silicon containing gas is controlled between about 1 sccm to about 10 slm by volume.

5. The method of claim 1 , further comprising:

annealing the substrate after deposition of the tungsten nitride layer on the substrate and prior to deposition of the conductive bulk layer.

6. The method of claim 1 , further comprising:

annealing the substrate after deposition of the conductive bulk layer.

7. The method of claim 1 , wherein the tungsten nitride layer is deposited by exposing the substrate to a gas mixture comprising a halogen-free precursor and a nitrogen containing reducing agent.

8. The method of claim 7 , wherein the halogen-free precursor comprises a tungsten metal organic compound selected from the group consisting of tungsten carbonyl (W(CO) 6 ), (tBuN═) 2 W(NMe 2 ) 2 , (tBuN═) 2 W(NEtMe) 2 , (tBuN═) 2 W(HNMe) 2 , W(OEt) 6 , W(OnPr) 6 , W(Cp) 2 H 2 , W(EtCP) 2 H 2 , W(iPrCp) 2 H 2 , W(NEt 2 ) 2 (NEt) 2 , and derivatives thereof.

9. The method of claim 7 , wherein the nitrogen containing reducing agent comprises nitrogen (N 2 ), nitrous oxide (N 2 O), or ammonia (NH 3 ).

10. The method of claim 1 , wherein the tungsten nitride layer further comprises:

a first tungsten nitride layer; and

a second thin tungsten rich tungsten nitride layer.

11. The method of claim 10 , wherein the second thin tungsten rich tungsten nitride layer contains about 50% to 90% tungsten and about 10% to about 50% nitrogen.

12. The method of claim 1 , wherein the tungsten nitride layer further comprises:

a first tungsten nitride layer; and

a second thin tungsten pure tungsten nitride layer.

13. The method of claim 12 , wherein the second thin tungsten pure tungsten nitride layer contains about 90% to 100% tungsten and about 0% to about 10% nitrogen.

14. The method of claim 1 wherein the conductive bulk layer comprises tungsten.

15. A method of fabricating a buried word line (bWL) feature used in a dynamic random access memory (DRAM), comprising:

forming a trench structure in a substrate, the trench structure having sidewalls and a bottom;

soaking the substrate in a silicon containing gas to form a silicon containing layer on the substrate;

exposing the substrate to a first processing gas comprising nitrogen and a second processing gas comprising a tungsten to deposit a first tungsten nitride layer on the silicon containing layer, wherein a tungsten silicide layer is formed at an interface between the silicon containing layer and the first tungsten nitride layer;

subjecting the first tungsten nitride layer to a nitridation treatment using active nitrogen species from a remote plasma;

depositing a second tungsten nitride layer on a surface of the first tungsten nitride layer using a third processing gas comprising nitrogen and a fourth processing gas comprising tungsten; and

depositing a tungsten bulk layer directly on a surface of the second tungsten nitride layer.

16. The method of claim 15 , further comprising:

annealing the substrate after deposition of the second tungsten nitride layer and prior to deposition of the tungsten bulk layer.

17. The method of claim 15 , wherein the second and fourth processing gases comprises a tungsten metal organic compound selected from the group consisting of tungsten carbonyl (W(CO) 6 ), (tBuN═) 2 W(NMe 2 ) 2 , (tBuN═) 2 W(NEtMe) 2 , (tBuN═) 2 W(HNMe) 2 , W(OEt) 6 , W(OnPr) 6 , W(Cp) 2 H 2 , W(EtCP) 2 H 2 , W(iPrCp) 2 H 2 , W(NEt 2 ) 2 (NEt) 2 , and derivatives thereof.