Method for plasma stripping using periodic modulation of gas chemistry and hydrocarbon addition

1. A method for etching a feature in a low-k dielectric layer through a photoresist etch mask over a substrate, comprising:

placing a low-k dielectric layer over a substrate;

placing a patterned photoresist mask over the low-k dielectric layer;

etching at least one feature into the low-k dielectric layer; and

performing a gas-modulated cyclic stripping process for more than three cycles for stripping a single photoresist mask, wherein each cycle comprises:

performing a protective layer forming phase using a first gas, wherein the protective layer forming phase is performed in about 0.005 to 10 seconds for each cycle, comprising;

providing the first gas; and

forming a plasma from the first gas, wherein a protective layer is formed on sidewalls of the at least one feature and a thickness of the protective layer is increased, wherein the protective layer is a layer of deposited material that is relatively inert to etching reactions with respect to the photoresist mask; and

performing a stripping phase for stripping the photoresist mask using a second gas, where the first gas is different than the second gas, wherein the etching phase is performed in about 0.005 to 10 seconds for each cycle, comprising:

providing the second gas; and

forming a plasma from the second gas, wherein the thickness of the protective layer is decreased and some of the photoresist mask is stripped.

2. The method, as recited in claim 1 , wherein the protective layer forming phase forms a layer less than 200 Å thick.

3. The method, as recited in claim 1 , wherein the protective layer forming phase forms a layer between about 0.1 and 100 Å thick.

4. The method, as recited in claim 3 , wherein performing a gas-modulated cyclic stripping process is performed in a capacitively coupled plasma process chamber.

5. The method, as recited in claim 1 , wherein the protective layer forming phase and the etching phase are performed in a common plasma processing chamber.

6. The method, as recited in claim 5 , wherein the common plasma processing chamber is a capacitively coupled plasma processing chamber, wherein the forming the plasma from the first gas comprises providing capacitively coupled energy.

7. The method, as recited in claim 6 , wherein the gas-modulated cyclic stripping process is performed for at least 3 cycles.

8. The method, as recited in claim 5 , wherein the first gas comprises a protective layer forming gas and the second gas comprises a stripping gas.

9. The method, as recited in claim 8 , wherein the protective layer forming gas is at least one of C 2 H 4 , CH 4 , CH 4 , C 2 H 4 , C 2 H 6 , C 2 H 2 , C 3 H 8 , CO, SiH 4 , Si(CH 3 ) 4 , Si(C 2 H 5 ) 4 CH 3 F, C 2 H 5 F, C 3 H 7 F, and C 2 H 3 F.

10. The method, as recited in claim 8 , wherein the stripping gas is at least one of O 2 , H 2 , N 2 , water vapor, CO 2 and NH 3 .

11. The method, as recited in claim 10 , wherein the first gas has a stripping gas to protective layer forming gas ratio of less than 1:1 and wherein the second gas has a stripping gas to protective layer forming gas ratio between 10:1 and 2:1.

12. The method, as recited in claim 1 , wherein the gas-modulated cyclic stripping process is performed for at least 3 cycles.

13. The method, as recited in claim 1 , wherein the first gas comprises a protective layer forming gas and the second gas comprises a stripping gas.

14. The method, as recited in claim 13 , wherein the protective layer forming gas is at least one of C 2 H 4 , CH 4 , CH 4 , C 2 H 4 , C 2 H 6 , C 2 H 2 , C 3 H 8 , CO, SiH 4 , Si(C 2 H 5 ) 4 CH 3 F, C 2 H 5 F, C 3 H 7 F, and C 2 H 3 F.

15. The method, as recited in claim 14 , wherein the stripping gas is at least one of O 2 , H2, N2, water vapor, CO 2 and NH3.

16. The method, as recited in claim 15 , wherein the first gas has a stripping gas to protective layer forming gas ratio of less than 1:1 and wherein the second gas has a stripping gas to protective layer forming gas ratio between 10:1 and 2:1.

17. A method for removing at least part of a single layer over a substrate, comprising:

performing a gas-modulated cyclic process for more than three cycles, wherein each cycle comprises:

performing a protective layer forming phase using first gas chemistry with a deposition gas chemistry, wherein the protective layer forming phase is performed in about 0.005 to 10 seconds for each cycle, comprising;

providing the first gas chemistry; and

forming a plasma from the first gas chemistry, which causes a protective layer formed and the thickness of the protective layer to increase, wherein the protective layer is a layer of deposited material that is relatively inert to etching reactions with respect to the substrate; and

performing a removal phase for removing at least part of the single layer using a second gas chemistry using a removal gas chemistry, where the first gas chemistry is different than the second gas chemistry, wherein the removal phase is performed in about 0.005 to 10 seconds for each cycle, comprising:

providing the second gas chemistry; and

forming a plasma from the second gas chemistry to cause removal of at least part of the single layer.

18. The method of claim 1 , wherein the first gas has a stripping gas to protective layer forming gas ratio of less than 1:1.

19. The method of claim 18 , wherein the first gas has a stripping gas to protective layer forming gas ratio of between 1:1 and 1:10.

20. The method of claim 1 , wherein the second gas has a stripping gas to protective layer forming gas ratio of between 10:1 and 2:1.