Method for reducing line width roughness with plasma pre-etch treatment on photoresist

1. A method for reducing line width roughness (LWR) of a feature in an etch layer below a patterned photoresist mask formed of a photoresist material and having mask features, the method comprising:

non-etching plasma pre-etch treatment of the photoresist mask, comprising:

providing a treatment gas containing H 2 and COS;

forming a plasma from the treatment gas;

stopping the treatment gas; and

etching a feature in the etch layer through the pre-treated photoresist mask using an etching gas:

wherein the non-etching plasma pre-etch treatment does not open or substantially etch the etch layer below the patterned photoresist mask through the patterned photoresist mask,

and wherein the etching the feature in the etch layer through the pre-treated photoresist mask reduces the LWR compared with etching of a feature in the etch layer through the patterned photoresist mask without performing the non-etching plasma pre-etch treatment of the photoresist mask.

2. The method as recited in claim 1 , wherein said non-etching plasma pre-etch treatment further comprises:

curing and smoothing surfaces of the mask features using the plasma formed from the treatment gas.

3. The method as recited in claim 2 , wherein said curing and smoothing includes:

reducing single and double C—O bonds from the surfaces of the photoresist mask using H 2 component; and

depositing materials on sidewalls of the mask features using COS component.

4. The method as recited in claim 3 , wherein a thickness of the deposited materials is less than 5 nm.

5. The method as recited in claim 1 , wherein H 2 and COS has at least 50% of a total flow of the treatment gas.

6. The method as recited claim 4 , wherein the treatment gas further contains N 2 and C 4 F 8 .

7. The method as recited claim 1 , wherein the treatment gas essentially consists of H 2 and COS.

8. The method as recited claim 1 , wherein a flow ratio of H 2 and COS is about 10:1 to 60:1.

9. The method as recited claim 1 , wherein a flow ratio of H 2 and COS is about 20:1 to 50:1.

10. The method as recited claim 1 , wherein said non-etching pre-etch treatment includes:

controlling a bias voltage such that the non-etching plasma pre-etch treatment does not open or substantially etch an underlying layer exposed through the mask features.

11. The method as recited claim 1 , wherein said forming the plasma includes:

applying a bias voltage between 0 to 500 V.

12. The method as recited claim 1 , wherein said forming the plasma includes:

applying a bias voltage between 0 to 150 V.

13. The method as recited claim 1 , wherein said non-etching pre-treating substantially preserves an original aspect ratio of the mask features.

14. A method for reducing line width roughness (LWR) of a feature in an etch layer below a patterned photoresist mask formed of a photoresist material and having mask features, the method comprising:

non-etching plasma pre-etch treatment of the photoresist mask, comprising:

providing a treatment gas containing H 2 and COS;

forming a plasma from the treatment gas;

stopping the treatment gas; and

etching a feature in the etch layer through the pre-treated photoresist mask using an etching gas,

wherein the non-etching plasma pre-etch treatment does not open or substantially etch the etch layer below the patterned photoresist mask through the patterned photoresist mask, and further comprises:

curing and smoothing surfaces of the mask features using the plasma formed from the treatment gas.

15. The method as recited in claim 14 , wherein said curing and smoothing includes:

reducing single and double C—O bonds from the surfaces of the photoresist mask using H 2 component; and

depositing materials on sidewalls of the mask features using COS component.

16. The method as recited in claim 15 , wherein a thickness of the deposited materials is less than 5 nm.

17. The method as recited claim 16 , wherein the treatment gas further contains N 2 and C 4 F 8 .

18. The method as recited in claim 14 , wherein H 2 and COS has at least 50% of a total flow of the treatment gas.

19. The method as recited claim 14 , wherein the treatment gas essentially consists of H 2 and COS.

20. The method as recited claim 14 , wherein said non-etching pre-treating substantially preserves an original aspect ratio of the mask features.