Methods to avoid unstable plasma states during a process transition

• US 20070066064A1
• Filed: 03/10/2006
• Published: 03/22/2007
• Est. Priority Date: 03/17/2000
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Hoffman, Daniel, Sinha, Ashok, Zhao, Xiaoye, Ma, Shawming, Kutney, Michael, Delgadino, Gerardo, Burns, Douglas, Gold, Ezra
• Granted Patent: US 8,048,806 B2
• Time in Patent Office: Days
• US Class Current: 438/689
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H01L 21/76807 for dual damascene structures

Abstract

In some implementations, a method is provided in a plasma processing chamber for stabilizing etch-rate distributions during a process transition from one process step to another process step. The method includes performing a pre-transition compensation of at least one other process parameter so as to avoid unstable plasma states by inhibiting formation of a parasitic plasma during the process transition. In some implementations, a method is provided for processing a workpiece in plasma processing chamber, which includes inhibiting deviations from an expected etch-rate distribution by avoiding unstable plasma states during a process transition from one process step to another process step.

Claims

1. A method in a plasma processing chamber for stabilizing etch-rate distributions during a process transition from one process step to another process step, wherein the process transition comprises changing of at least one process parameter, the method comprising performing a pre-transition compensation of at least one other process parameter so as to avoid unstable plasma states by inhibiting formation of a parasitic plasma during the process transition.

2. The method of claim 1 wherein performing a pre-transition compensation comprises increasing a chamber pressure prior to the process transition.

3. The method of claim 2 further comprising reducing the chamber pressure for processing after the process transition.

4. The method of claim 2 wherein performing the pre-transition compensation comprises increasing a chamber pressure prior to the process transition if a source power-to-bias power ratio is greater than about 1.

5. The method of claim 1 wherein performing the pre-transition compensation comprises changing a gas chemistry in the chamber to a non-reactive gas prior to the process transition.

6. The method of claim 5 wherein introducing the non-reactive gas into the plasma processing chamber prior to the process transition comprises starting a flow of the non-reactive gas to the process chamber before the process transition at a time prior to the process transition greater than a residence time of the non-reactive gas to arrive from a gas panel to the processing chamber.

7. The method of claim 6 wherein introducing the non-reactive gas into the plasma processing chamber comprises introducing argon at least 2 seconds prior to the process transition.

8. The method of claim 5 further introducing a reactive gas after the process transition for processing a workpiece.

9. The method of claim 5 wherein performing the pre-transition compensation comprises changing a gas chemistry in the chamber to a non-reactive gas prior to the process transition if a source power-to-bias power ratio is greater than about 1.

10. The method of claim 2 wherein performing the pre-transition compensation comprises setting a source power-to-bias power ratio within a range below about 1 for the transition.

11. The method of claim 2 wherein performing the pre-transition compensation comprises initiating a bias power prior to the process transition.

12. The method of claim 11 wherein initiating the bias power comprises setting bias power to about 100 W prior to the process transition.

13. The method of claim 1 wherein performing the pre-transition compensation comprises increasing a sheath size above a workpiece being processed by initiating application of a bias power prior to the process transition.

14. A method for processing a workpiece in plasma processing chamber, the method comprising inhibiting deviations from an expected etch-rate distribution by avoiding unstable plasma states during a process transition from one process step to another process step.

15. The method of claim 14 comprising changing at least one process parameter with a smooth non-linear transition during the process transition.

16. The method of claim 15 wherein changing the at least one process parameter with the smooth non-linear transition comprises changing the at least one process parameter along on of:

(a) a Boltzmann curve;

or (b) a Sigmoidal Richards curve.

17. The method of claim 15 wherein changing the at least one process parameter comprises gradually changing from a first steady state to a transition state and gradually changing from the transition state to a second steady state.

18. The method of claim 15 wherein changing of the at least one process parameter with the smooth non-linear transition comprises changing at least one of:

(a) a plasma source power;

(b) a bias power;

(c) a gas flow;

(d) a chamber pressure;

or (e) a magnetic field strength.

19. The method of claim 15 wherein changing at least one process parameter with a smooth non-linear transition is performed if a source power-to-bias power ratio is greater than about 1.

20. A method for avoiding unstable plasma states in a plasma processing chamber during a process transition from one process step to another process step, the method comprising sequentially changing selected process parameters such that a plasma is able to stabilize after each change prior to changing a next selected process parameter.

21. The method of claim 20 comprising inhibiting formation of a parasitic plasma during a process transition.

22. The method of claim 20 wherein changing the selected process parameters comprises providing a non-reactive gas chemistry in the chamber prior to changing other process parameters so as to inhibit formation of a parasitic plasma during a process transition.

23. The method of claim 20 wherein changing the selected process parameters comprises changing a source power after increasing a chamber pressure so as to inhibit formation of a parasitic plasma during a process transition.

24. The method of claim 20 wherein changing the selected process parameters comprises changing a source power after providing a non-reactive gas chemistry in the plasma processing chamber so as to inhibit formation of a parasitic plasma during a process transition.

25. The method of claim 20 wherein changing the selected process parameters comprises changing a source power after initiating application of a bias power on the workpiece so as to inhibit formation of a parasitic plasma during a process transition.

26. A method for inhibiting deviations from an expected etch-rate distribution in a plasma processing chamber during a process transition from one process step to another process step, the method comprising:

a) monitoring an surrogate characteristic of a plasma in a steady state;

b) monitoring the surrogate characteristic of the plasma during a process transition; and

c) limiting a change in the surrogate characteristic of the plasma during the process transition so as to inhibit formation of parasitic plasma.

27. The method of claim 26 wherein monitoring the surrogate parameter comprises monitoring at least one of:

(a) a plasma impedance;

(b) a plasma conductance;

(c) a plasma spectroscopic measurement;

(d) a plasma bias voltage;

or (e) a plasma bias current.

28. The method of claim 26 wherein limiting the change in the surrogate characteristic during the process transition comprises compensating at least one process parameter.

29. The method of claim 26 further comprising limiting the change in an impedance of the plasma during the process transition to less than about 2 times the value of the impedance during the steady state.

30. The method of claim 26 further comprising limiting the change in an impedance of the plasma during the process transition to less than about one-half of a value of the impedance of the plasma in the steady state.

31. The method of claim 26 further comprising:

a) limiting an increase in an impedance of the plasma during the process transition to less than about 2 times a value of the impedance of the plasma during the steady state; and

b) limiting a decrease in the impedance of the plasma during the process transition to less than about one-half of the value of the impedance of the plasma in the steady state.

32. The method of claim 26 comprising comparing an impedance of the plasma in the steady state with the impedance of the plasma in the process transition and limiting a value of the impedance of the plasma during the transition based on a steady state value of the impedance of the plasma prior to the transition.