Method of plasma etching with parallel plate reactor having a grid

• US 5,015,331 A
• Filed: 08/10/1990
• Issued: 05/14/1991
• Est. Priority Date: 08/30/1988
• Status: Expired due to Fees

• Current Assignee: Matrix Integrated Systems, Inc. (Axcelis Technologies Incorporated)
• Original Assignee: Matrix Integrated Systems, Inc. (Axcelis Technologies Incorporated)
• Inventors: Powell, Gary B.
• Primary Examiner(s): Schor, Kenneth M.
• Assistant Examiner(s): BRUCKNER, JOHN
• Application Number:
  US07/566,860
• Time in Patent Office: 277 Days
• Field of Search: 156/643, 156/646, 156/662, 156/640, 204/298.34
• US Class Current: 438/723
• CPC Class Codes: H01L 21/31116 by dry-etching

Abstract

A parallel plate reactor having a grounded grid disposed between an RF powered electrode and a grounded electrode upon which a substrate is disposed. A method of utilizing the above apparatus consists of etching the substrate using a composition of 30-100% NF₃ (nitrogen trifluoride) at 25 SCCM (standard cubic centimeter per minute) and 0-70% He (helium) at 75 SCCM to etch a layer of PECVD (plasma enchanced chemcial vapor deposition) Si₃ N₄ (silicon nitride). The etching takes place at 200 mtorr to 5 torr pressure and 50-400 watts RF power.

Claims

1. A method of etching a substrate comprising the steps of:

placing the substrate on a surface in an apparatus comprising an upper electrode coupled to an R-F power source, a lower electrode and a grid having openings defined therein and disposed between said upper electrode and said lower electrode, said grid and upper electrode forming an upper chamber therebetween, said grid being clamped to have the same potential at all times as the lower electrode and forming with the lower electrode a lower chamber therebetween;

passing a reactant gas into said upper chamber;

subjecting said gas to an R-F field applied via said upper electrode to generate in said upper chamber a plasma including ions in said upper chamber;

passing ions generated by said plasma through said grid toward said lower chamber; and

etching said substrate on said surface, said surface being in said lower chamber, said substrate being etched by said ions.

2. The method of claim 1 wherein said reactant gas comprises a fluorine source gas.

3. The method of claim 2 wherein said fluorine source gas comprises nitrogen trifluoride.

4. The method of claim 2 wherein said fluorine source gas comprises carbon tetraflouride.

5. The method of claim 2 wherein said fluorine source gas comprises sulfur hexafluoride.

6. The method of claim 1 wherein the substrate comprises a semiconductor device.

7. The method of claim 6 wherein said reactant gas comprises a fluorine source gas.

8. The method of claim 7 wherein said fluorine source gas comprises nitrogen trifluoride.

9. The method of claim 7 wherein said fluorine source gas comprises carbon tetraflouride.

10. The method of claim 7 wherein said fluorine source gas comprises sulfur hexafluoride.

11. The method of claim 1 wherein said substrate includes a layer of silicon nitride and the reactant gas is nitrogen trifluoride.

12. The method of claim 11 in which said upper electrode is coupled to a power source in the range of approximately 50-400 watts.

13. The method of claim 12 wherein said power source is approximately 175 watts.

14. The method of claim 11 in which the nitrogen trifluoride concentration is in the of approximately 30-100% with the remainder being helium.

15. The method of claim 14 wherein the nitrogen, trifluoride concentration is approximately 50% with the remainder being helium and said helium is supplied at a rate of approximately 75 standard cubic centimeters per minute.

16. The method of claim 11 wherein said etching occurs in the range of 200 millitorr to 5 torr pressure.

17. The method of claim 16 wherein said etching occurs at approximately 600 millitorr.

18. The method of claim 1 wherein the substrate includes a layer comprising a low pressure chemical vapor deposition of silicon nitride.

19. The method of claim 18 in which said upper electrode is coupled to a power source in the range of approximately 50-150 watts.

20. The method of claim 19 wherein said power source is approximately 50 watts.

21. The method of claim 18 in which the nitrogen trifluoride concentration is in the range of approximately 20-80% with the remainder being oxygen.

22. The method of claim 21 wherein the nitrogen trifluoride concentration is approximately 67% with the remainder being oxygen and said oxygen is supplied at a rate of approximately 25 standard cubic centimeters per minute.

23. The method of claim 18 wherein said etching occurs in the range of 200 millitorr to 5 torr pressure.

24. The method of claim 23 wherein said etching occurs at approximately 500 millitorr.

25. The method of claim 18 wherein said lower electrode is cooled to approximately 60°

C.

26. The method of claim 1 wherein the substrate includes a layer of an impurity doped oxide and the reactant gas is nitrogen trifluoride.

27. The method of claim 26 wherein said impurity doped oxide comprises phosphorous doped oxide.

28. The method of claim 26 wherein said impurity doped oxide comprises boron doped oxide.

29. The method of claim 26 in which said upper electrode is coupled to a power source in the range of approximately 50-400 watts.

30. The method of claim 29 wherein said power source is approximately 300 watts.

31. The method of claim 26 in which the nitrogen trifluoride concentration is in the range of approximately 30-100% with the remainder being helium.

32. The method of claim 31 wherein the nitrogen trifluoride concentration is approximately 50% with the remainder being helium and said helium is supplied at a rate of approximately 50 standard cubic centimeters per minute.

33. The method of claim 26 wherein said etching occurs in the range of 200 millitorr to 5 torr pressure.

34. The method of claim 33 wherein said etching occurs at approximately 1.5 torr.