Bias voltage adjustment approach for SiO / SiN layer alternating etching process

Abstract

The embodiments of the present disclosure generally relate to a method for etching a film stack with high selectivity and low etch recipe transition time. In one embodiment, a method for etching a film stack having a stacked pair of oxide and nitride layers is described. The method includes transferring a substrate having a film stack formed thereon into a process chamber, providing a first bias voltage to the substrate, etching an oxide layer of the film stack while providing the first bias voltage to the substrate, providing a second bias voltage to the substrate, the second bias voltage being greater than the first bias voltage, and etching a nitride layer of the film stack while providing the second bias voltage to the substrate.

Claims

1. 1. A method for etching a film stack having a laminated pair of oxide and nitride layers, comprising: transporting the substrate having the film stack formed thereon into a processing chamber; providing a first bias voltage to the substrate; etching an oxide layer of the film stack while providing the first bias voltage to the substrate; providing a second bias voltage to the substrate that is greater than the first bias voltage; and etching a nitride layer of the film stack while providing the second bias voltage to the substrate.

2. The method of claim 1 , wherein providing the second bias voltage occurs after etching the oxide layer of the film stack.

3. 2. The method of claim 1, wherein the oxide layer of the film stack is silicon oxide (SiO) and the nitride layer of the film stack is silicon nitride (SiN).

4. 4. The method of claim 3, wherein the first bias voltage is from about 0 kV to about 3 kV and the second bias voltage is from about 2 kV to about 8 kV.

5. providing a process gas mixture to the substrate, the process gas mixture comprising: N F M , C X H Y F Z and oxygen.

6. 6. The method of claim 5, wherein the oxygen comprises about 25% to about 50% by volume of the process gas mixture.

7. 6. The method of claim 5, wherein the composition of the process gas mixture remains substantially the same during the etching of the oxide layer and the etching of the nitride layer.

8. Said C N F M Gas is C 2 F 4 , C 4 F 8 , C 3 F 6 , and C 4 F 6 wherein C is selected from the group consisting of X H Y F Z Gas is CHF 3 , C.H. 2 F 2 , and C.H. 3 6. The method of claim 5, wherein the compound is selected from the group consisting of:

9. 2. The method of claim 1, wherein the oxide layer and the nitride layer are each about 20 nm to about 30 nm thick.

10. 1. A method for etching a film stack having a laminated pair of oxide and nitride layers, comprising: transporting the substrate having the film stack formed thereon into a process chamber; The substrate is N F M , C X H Y F Z providing a process gas mixture comprising: providing a first bias voltage to the substrate; etching a first oxide layer of the film stack while providing the first bias voltage to the substrate and while providing the process gas mixture to the substrate; providing a second bias voltage to the substrate that is greater than the first bias voltage; etching a nitride layer of the film stack while providing the second bias voltage to the substrate and while providing the process gas mixture to the substrate; providing a third bias voltage to the substrate that is less than the second bias voltage; and etching a second oxide layer of the film stack while providing the third bias voltage to the substrate and while providing the process gas mixture to the substrate.

11. 11. The method of claim 10, wherein the oxide layer of the film stack is silicon oxide (SiO) and the nitride layer of the film stack is silicon nitride (SiN).

12. 12. The method of claim 11, wherein the first bias voltage is from about 0 kV to about 3 kV and the second bias voltage is from about 2 kV to about 8 kV.

13. 13. The method of claim 12, wherein the first bias voltage is about 0 kV and the second bias voltage is about 2 kV.

14. 14. The method of claim 13, wherein etching the oxide layer achieves an oxide-to-silicon nitride etch selectivity of about 3.2 or greater.

15. 14. The method of claim 13, wherein etching the nitride layer achieves a silicon nitride-to-oxide etch selectivity of about 1.4 or greater.

16. Said C N F M Gas is C 2 F 4 , C 4 F 8 , C 3 F 6 , and C 4 F 6 wherein C is selected from the group consisting of X H Y F Z Gas is CHF 3 , C.H. 2 F 2 , and C.H. 3 The method of claim 10, wherein the compound is selected from the group consisting of:

17. The method of claim 10 , wherein the first bias voltage and the second bias voltage increase as an aspect ratio increases.

18. 1. A method for etching a film stack having a laminated pair of silicon oxide and silicon nitride layers, comprising: transporting the substrate having the film stack formed thereon into a process chamber; The substrate is N F M , C X H Y F Z and oxygen, said oxygen comprising about 25% to about 50% by volume of said process gas mixture; providing a first bias voltage to the substrate; etching a first silicon oxide layer of the film stack while providing the first bias voltage to the substrate and while providing the process gas mixture to the substrate; providing a second bias voltage to the substrate that is greater than the first bias voltage; etching a silicon nitride layer of the film stack while providing the second bias voltage to the substrate and while providing the process gas mixture to the substrate; providing the first bias voltage to the substrate; and etching a second silicon oxide layer of the film stack while providing the first bias voltage to the substrate and while providing the process gas mixture to the substrate.

19. 20. The method of claim 18, wherein providing the second bias voltage occurs after etching the first silicon oxide layer of the film stack.

20. 20. The method of claim 18, wherein the first bias voltage and the second bias voltage increase as an aspect ratio increases.

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