Post etch treatment to prevent pattern collapse

1. A method for etching features in a stack comprising a patterned hardmask over a carbon based mask layer over an etch layer, comprising:

transferring a pattern from the patterned hardmask to the carbon based mask layer, comprising:

providing a flow of a transfer gas comprising an oxygen containing component and at least one of SO 2 or COS;

forming the transfer gas into a plasma;

providing a bias of greater than 10 volts to accelerate ions from the plasma to the carbon based mask layer, which transfers the pattern to the carbon based mask layer; and

stopping the flow of the transfer gas; and

providing a post treatment, comprising:

providing a flow of a post treatment gas comprising at least one of He, Ar, N 2 , H 2 , or NH 3 , wherein the flow is provided to maintain a processing pressure of between 50 mTorr and 500 mTorr inclusive;

forming the post treatment gas into a plasma;

providing a bias of greater than 20 volts to accelerate ions from the plasma to the carbon based mask layer; and

stopping the flow of the post treatment gas.

2. The method, as recited in claim 1 , further comprising etching the etch layer through the carbon based mask layer.

3. The method, as recited in claim 2 , wherein patterned hardmask is of a silicon based material.

4. The method, as recited in claim 3 , wherein the silicon based material is at least one of silicon nitride, silicon oxynitride, amorphous silicon, or polysilicon.

5. The method, as recited in claim 4 , wherein the carbon based mask layer comprises amorphous carbon.

6. The method, as recited in claim 5 , wherein the transferring the pattern forms a sulfur containing sidewall passivation.

7. The method, as recited in claim 6 , wherein the post treatment step removes or changes the sulfur containing sidewall passivation.

8. The method, as recited in claim 7 , wherein the etch layer is at least one of silicon oxide, silicon nitride, or tungsten nitride.

9. The method, as recited in claim 8 , wherein the transferring the pattern from the patterned hardmask to the carbon based mask layer forms mask features in the carbon based mask, wherein the mask features are lines or 2-dimensional array of pillars.

10. The method, as recited in claim 9 , wherein the mask features have a height to width aspect ratio of greater than 2.5:1.

11. The method, as recited in claim 10 , wherein the mask features have a period or pitch less than 100 nm.

12. The method, as recited in claim 1 , wherein patterned hardmask is of a silicon based material.

13. The method, as recited in claim 1 , wherein the carbon based mask layer comprises amorphous carbon.

14. The method, as recited in claim 1 , wherein the transferring the pattern forms a sulfur containing sidewall passivation.

15. The method, as recited in claim 14 , wherein the post treatment step removes or changes the sulfur containing sidewall passivation.

16. The method, as recited in claim 1 , wherein the transferring the pattern from the patterned hardmask to the carbon based mask layer forms mask features in the carbon based mask, wherein the mask features are lines or 2-dimensional array of pillars.

17. The method, as recited in claim 1 , wherein the mask features have a height to width aspect ratio of greater than 2.5:1.

18. The method, as recited in claim 1 , wherein the mask features have a period or pitch less than 100 nm.