Method of forming carbon-containing silicon nitride layer

1. A method for forming a gate, comprising:

providing a substrate having a gate dielectric layer thereon;

forming a conductive layer on the gate dielectric layer;

patterning the conductive layer and the gate dielectric layer to form a gate electrode;

forming offset spacers on the sidewalls of the gate electrode, the material of the offset spacers is carbon-containing silicon nitride;

forming a material layer over the substrate and covering the gate electrode, wherein the material layer comprises a carbon-containing silicon nitride layer formed by low pressure chemical vapor deposition (LPCVD) using disilane, ammonia and at least a carbon-source precursor as reactant gases;

etching back the material layer to form spacers over sidewalls of the gate electrode; and

forming a source/drain region in the substrate.

2. The method according to claim 1 , wherein the carbon-containing silicon nitride layer has a carbon content higher than 9%.

3. The method according to claim 2 , wherein the carbon-containing silicon nitride layer is formed by a single wafer tool.

4. The method according to claim 1 , the step of forming the offset spacers comprises:

forming a carbon-containing silicon nitride offset material layer over the substrate; and

etching back the carbon-containing silicon nitride offset material layer to form the offset spacers on the sidewalls of the gate electrode.

5. The method according to claim 4 , wherein the carbon-containing silicon nitride offset material layer is formed by low pressure chemical vapor deposition (LPCVD) using disilane, ammonia and at least a carbon-source precursor as reactant gases.

6. The method according to claim 5 , wherein the carbon-containing silicon nitride offset material layer has a carbon content higher than 9%.

7. The method according to claim 5 , wherein the carbon-containing silicon nitride offset material layer is formed by a single wafer tool.

8. The method according to claim 1 , wherein the carbon-source precursor is selected from the group consisting of TEASAT (triethylarsenate, C 6 H 15 AsO 4 ), Trans-LC (C 2 H 2 Cl 2 ), TCS SiHCl 3 ),TMAl (trimethyl aluminum Al(CH 3 ) 3 ), C 2 H 4 , C 3 H 6 , TEB (triethylborate, B(OC 2 H 5 ) 3 ), TEPO (triethylphosphate, PO(C 2 H 5 O) 3 ), TDMAT (tetrakis-dimethylamino titanium, Ti[N(CH 3 ) 2 ] 4 ) and combinations thereof.

9. The method according to claim 5 , wherein the carbon-source precursor is selected from the group consisting of TEASAT (triethylarsenate, C 6 H 15 AsO 4 ), Trans-LC (C 2 H 2 Cl 2 ), TCS trichlorosilane, SiHCl 3 ), TMAl (trimethyl aluminum, Al(CH 3 ) 3 ), C 2 H 4 , C 3 H 6 , TEB (triethylborate, B(OC 2 H 5 ) 3 ), TEPO (triethylphosphate, PO(C 2 H 5 O) 3 ), TDMAT (tetrakis-dimethylamino titanium, Ti[N(CH 3 ) 2 ] 4 ) and combinations thereof.

10. The method according to claim 1 , wherein the carbon-containing silicon nitride layer has a carbon content ranging from about 9% to about 30%.

11. The method according to claim 1 , wherein a gas flow rate of disilane (Si 2 H 6 ) is less than 50 sccm (standard cubic centimeter per minute).

12. The method according to claim 1 , wherein a gas flow rate of the carbon-source precursor is less than 2 slm (standard liter per minute).

13. The method according to claim 1 , wherein a reaction pressure is below 250 Torr.

14. The method according to claim 1 , wherein a reaction temperature is below 800° C.