Method for manufacturing a semiconductor device having a W/WN/polysilicon layered film

1. A method of manufacturing a semiconductor device comprising:

consecutively depositing a silicon (Si) layer, a tungsten nitride (WN) layer, and a tungsten (W) layer on a silicon oxide layer;

forming a mask pattern on said W layer;

selectively etching said W layer by using plasma generated in a first etching gas having a high W/WN etch selectivity ratio and using said mask pattern as an etching mask;

selectively etching said WN layer and said Si layer by using plasma generated in a second etching gas having a high WN/Si etch selectivity ratio and using said mask pattern as an etching mask; and

selectively etching said Si layer by using plasma generated in a third etching gas having a high Si/SiO 2 etch selectivity ratio and using said mask pattern as an etching mask.

2. The method according to claim 1 , wherein said second gas includes fluorocarbon.

3. The method according to claim 1 , wherein said first etching gas includes at least one of SF 6 and NF 3 , and N 2 without including fluorocarbon.

4. The method according to claim 3 , wherein said second gas includes fluorocarbon.

5. The method according to claim 4 , wherein said second etching gas includes at least one gas selected from the group consisting of CHF 3 , CH 2 F 2 , CH 3 F, C 2 F 6 , C 3 F 6 , C 4 F 6 and C 4 F 8 .

6. The method according to claim 1 , wherein said selectively etching said W layer is finished at a timing when a W luminescence at a wavelength of reaction product of W abruptly falls in a spectrum analysis of said plasma in said etching gas.

7. The method according to claim 6 , wherein said wavelength is between 400 nm and 600 nm.

8. The method according to claim 1 , further comprising depositing a SiN film to cover exposed surfaces between said selectively etching said W layer and said selectively etching said Si layer.

9. The method according to claim 1 , wherein said first etching gas is devoid of fluorocarbon.

10. The method according to claim 1 , wherein said first etching gas comprises a mixture of SF 6 , Cl 2 , and N 2 .

11. The method according to claim 1 , wherein said first etching gas comprises a gas mixture having a mixture ratio of 20% for N 2 to (N 2 +SF 6 ).

12. The method according to claim 1 , wherein said second etching gases comprises at least one gas selected from the group consisting of CHF 3 , CH 2 F 2 , CH 3 F, C 2 F 6 , C 3 F 6 , C 4 F 6 and C 4 F 8 , mixed with Cl 2 , O 2 , and N 2 .

13. The method according to claim 1 , wherein said second etching gases comprises a mixture of CF 4 , mixed with Cl 2 , O 2 , and N 2 .

14. The method according to claim 1 , wherein said third etching gas comprises a mixture of HBr and O 2 .

15. A method of manufacturing a semiconductor device comprising:

depositing a silicon layer, a tungsten nitride layer, and a tungsten layer on a base layer;

selectively etching said tungsten layer by using plasma generated in a first etching gas;

selectively etching said tungsten nitride layer and said silicon layer by using plasma generated in a second etching gas; and

selectively etching said silicon layer by using plasma generated in a third etching gas.

16. A method of manufacturing a semiconductor device comprising:

depositing a silicon layer, a tungsten nitride layer, and a tungsten layer on a base layer;

selectively etching said tungsten layer by using plasma generated in a first etching gas having a high W/WN etch selectivity ratio;

selectively etching said tungsten nitride layer and said silicon layer by using plasma generated in a second etching gas having a high WN/Si etch selectivity ratio; and

selectively etching said silicon layer by using plasma generated in a third etching gas having a high Si/SiO 2 etch selectivity ratio.