In-situ photoresist strip during plasma etching of active hard mask

1. A method for etching features in a silicon layer, comprising

forming a hard mask layer over the silicon layer, wherein the hard mask layer is silicon-based, wherein the forming the hard mask layer comprises:

forming a first layer over the silicon layer, wherein the first layer is Si 3 N 4 ; and

forming a second layer over the first layer, wherein the second layer is SiO 2 ;

forming a photoresist layer over the hard mask layer;

opening the hard mask layer; and

stripping the photoresist layer, comprising

providing a stripping gas;

forming a plasma with the stripping gas by providing a high frequency RF power with a frequency greater than or equal to 27 MHz and a low frequency RF power with a frequency less than 20 MHz, wherein the low frequency RF power has a power less than 50 watts; and

stopping the stripping gas when the photoresist layer is stripped.

2. The method, as recited in claim 1 , wherein the opening the hard mask layer and the stripping the photoresist layer are performed in a same chamber.

3. The method, as recited in claim 2 , wherein the low frequency RF power has a power of 0 watt.

4. The method, as recited in claim 3 , wherein the high frequency RF power has a power between approximately 200 watts and 800 watts.

5. The method, as recited in claim 4 , wherein the opening the hard mask layer comprises

providing an opening gas;

forming a plasma with the opening gas by providing a high frequency RF power and a low frequency RF power; and

stopping the opening gas when the hard mask layer is opened.

6. The method, as recited in claim 5 , further comprising:

forming a bottom anti-reflection coating layer over the hard mask layer and under the photoresist layer;

opening the bottom anti-reflection coating layer; and

stripping the bottom anti-reflection coating layer.

7. The method, as recited in claim 6 , wherein the opening the bottom anti-reflection coating layer, the opening the hard mask layer, the stripping the bottom anti-reflection coating layer, and the stripping the photoresist layer are performed in a same chamber.

8. The method, as recited in claim 6 , wherein the stripping the bottom anti-reflection coating layer comprises:

providing a stripping gas;

forming a plasma with the stripping gas by providing a high frequency RF power and a low frequency RF power, wherein the low frequency RF power has a power less than 50 watts; and

stopping the stripping gas when the bottom anti-reflection coating layer is stripped.

9. The method, as recited in claim 5 , further comprising:

etching the silicon layer; and

stripping the hard mask layer.

10. The method, as recited in claim 5 , wherein the forming a plasma with the opening gas for opening the hard mask layer comprises providing a high frequency RF power between 150 and 800 watts and providing a low frequency RF power between 300and 1200 watts.

11. The method, as recited in claim 3 , wherein the high frequency RF power has a power of approximately 300 watts.

12. The method, as recited in claim 1 , wherein the stripping gas comprises at least one gas selected from the group consisting of O 2 , N 2 , and H 2 .

13. The method, as recited in claim 12 , wherein the stripping gas further comprises halogen.

14. The method, as recited in claim 1 , wherein the silicon layer is a silicon wafer.

15. A method for etching features in a silicon layer, comprising

forming a hard mask layer over the silicon layer;

forming a bottom anti-reflection coating layer over the hard mask layer;

forming a photoresist layer over the bottom anti-reflection coating layer;

opening the bottom anti-reflection coating layer;

opening the hard mask layer;

stripping the bottom anti-reflection coating layer comprising; and

providing a stripping gas;

forming a plasma with the stripping gas by providing a high frequency RF power with a frequency greater than or equal to 27 MHz and a low frequency RF power with a frequency less than 20 MHz, wherein the low frequency RF power has a power less than 50 watts; and

stopping the stripping gas when the photoresist layer is stripped;

stripping the photoresist layer, comprising

providing a stripping gas;

forming a plasma with the stripping gas by providing a high frequency RF power with a frequency greater than or equal to 27 MHz and a low frequency RF power with a frequency less than 20 MHz, wherein the low frequency RF power has a power less than 50 watts; and

stopping the stripping gas when the photoresist layer is stripped.

16. The method, as recited in claim 15 , wherein the opening the bottom anti-reflection coating layer, the opening the hard mask layer, the stripping the bottom anti-reflection coating layer, and the stripping the photoresist layer are performed in a first chamber.

17. The method, as recited in claim 16 , further comprising

etching the silicon layer; and

stripping the hard mask layer,

wherein the etching the silicon layer and the stripping the hard mask layer are preformed in a second chamber.

18. The method, as recited in claim 15 , wherein the low frequency RF power has a power of 0 watt.