Method for etching low k dielectrics

• US 6,547,977 B1
• Filed: 07/05/2000
• Issued: 04/15/2003
• Est. Priority Date: 04/02/1998
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Hsueh, Gary C., Ye, Yan, Ma, Diana Xiaobing, Yan, Chun
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): Mercado, Julian
• Application Number:
  US09/610,915
• Time in Patent Office: 1,014 Days
• Field of Search: 216/57, 216/67, 216/74, 216/79, 216/81, 216/72, 216/64, 438/725, 438/735, 438/737, 438/742, 438/743, 204/192.31, 204/192.35, 204/192.36, 204/192.37
• US Class Current: 216/72
• CPC Class Codes: H01L 21/31138 by dry-etching

Abstract

The present disclosure pertains to a method for plasma etching of low k materials, particularly polymeric-based low k materials. Preferably the polymeric-based materials are organic-based materials. The method employs an etchant plasma where the major etchant species are generated from a halogen other than fluorine and oxygen. The preferred halogen is chlorine. The volumetric (flow rate) ratio of the halogen:oxygen in the plasma source gas ranges from about 1:20 to about 20:1. The atomic ratio of the halogen:oxygen preferably falls within the range from about 1:20 to about 20:1. When the halogen is chlorine, the preferred atomic ratio of chlorine:oxygen ranges from about 1:10 to about 5:1. When this atomic ratio of chlorine:oxygen is used, the etch selectivity for the low k material over adjacent oxygen-comprising or nitrogen-comprising layers is advantageous, typically in excess of about 10:1. The plasma source gas may contain additives in an amount of 15% or less by volume which are designed to improve selectivity for the low k dielectric over an adjacent material, to provide a better etch profile, or to provide better critical dimension control, for example. When the additive contains fluorine, the amount of the additive is such that residual chlorine on the etched surface of the low k material comprises less than 5 atomic %.

Claims

1. A method for selectively plasma etching an opening into a low k dielectric material to produce a cavity useful in forming a conductive interconnect structure, said method comprising:

selectively etching a low k dielectric material relative to an adjacent oxide or nitride or combination thereof, by contacting said low k dielectric material with a plasma generated from a plasma source gas comprising oxygen and a halogen-comprising gas where said halogen is not fluorine, and wherein an etch selectivity is at least 10;

1 for said low k dielectric material relative to said adjacent oxide or nitride or combination thereof.

2. The method of claim 1, wherein said source gas includes a halogen-comprising gas selected from the group consisting of Cl₂, Br₂,I₂, ICl, IBr, BrCl, HCl, BCl₃, CHCl₃, CH₂Cl₂, CCl₄, C₂H₃Cl₃, C₂H₄Cl₂, SiCl₄, HBr, CH₃Br, C₂H₂Br₂Cl₂, HI, CCl₂O, CCl₃NO₂, and combinations thereof.

3. The method of claim 1, or claim 2, wherein said halogen is chlorine.

4. The method of claim 2, wherein said source gas includes an oxygen-comprising gas selected from the group consisting of O₂, CO, CO₂, CH₄O, C₂H₆O, N₂O, NO₂, O₃, H₂O, and combinations thereof.

5. The method of claim 1, or claim 2, or claim 4, wherein an additive is used in combination with said oxygen and said halogen-comprising gas, and wherein said additive is less than about 15 volumetric percent of the total plasma source gas supply.

6. The method of claim 5, wherein said additive is selected from the group consisting of N₂;

H₂;

C_xH_y;

CF₄;

NF₃; and

combinations thereof, where x is less than about 3 and y is less than about 8.

7. The method of claim 5, wherein said additive is selected from the group consisting of N₂, H₂, C_xH_y, CF₄, NF₃, helium, neon, argon, krypton, xenon, and combinations thereof, wherein x is less than about 3, and y is less than about 8.

8. The method of claim 3, wherein an etch rate for said low k dielectric material using said source gas comprising chlorine and oxygen is at least about 8,000 Å

/min.

9. The method of claim 1, wherein said low k dielectric material is a polymer-based material.

10. The method of claim 9, wherein said polymer-based material is an organic-based material.

11. The method of claim 1, wherein an atomic ratio of said halogen to said oxygen ranges from about 1:

20 to about 20;

1.

12. The method of claim 11, wherein said atomic ratio of said chlorine to said oxygen ranges from about 1:

10 to about 5;

1.

13. The method of claim 1, wherein said plasma source gas contains an additive in the amount of 15% or less in volume, which additive improves selectivity for etching said low k dielectric material over an adjacent material, or improves an etch profile, or improves control over a critical etched dimension.

14. The method of claim 13, wherein said additive improves selectivity for etching said low k dielectric material relative to an oxide which contains at least 30 atomic percent oxygen.

15. The method of claim 14, wherein said oxide is an oxide of silicon.

16. The method of claim 13, wherein said additive improves selectivity for etching said low k dielectric material relative to a nitride which contains at least 30 atomic percent nitrogen.

17. The method of claim 16, wherein said nitride is a nitride of silicon.

18. The method of claim 1 or claim 13, wherein said low k dielectric material does not contain silicon.

19. The method of claim 1 or claim 13, wherein said low k dielectric material is selected from the group consisting of Poly(arylene)ethers;

Poly(arylene)ether oxazoles;

Fluorinated poly(arylene)ethers;

Parylene-N;

Parylene-F;

Parylene-AF;

Parylene-AF4;

Polyimides;

Polynapthalene-N;

Polynaphthalene-F;

Perfluorocyclobutene;

Polytetrafluoroethylene;

Polyphenyl-Quinoxalines;

Polybenzoxazoles;

Polyindane;

Polynorborene;

Polystyrene;

Polyphenyleneoxide;

Polyethylene;

Polypropylene;

alpha-carbons;

SILK™

, and combinations thereof.

20. The method of claim 1 or claim 13, wherein said low k dielectric material is selected from the group consisting of BCB, FPI, SILK™

, FLARE™

2.0, and combinations thereof.

21. The method of claim 1, wherein said combination of oxide and nitride is silicon oxynitride.

22. The method of claim 1, wherein said low k dielectric material is uniformly etched within 10% or less of 1 σ

across a wafer surface.

23. A method for selectively plasma etching back a low k dielectric material deposited over the surface of a patterned conductive material, to provide isolation of conductive lines and contacts, wherein said low k dielectric material is selectively etched relative to an adjacent oxide or nitride or combination thereof, by contacting said low k dielectric material with a plasma generated from a non-fluorine-containing source gas comprising chlorine and oxygen, and wherein an etch selectivity for said low k dielectric material relative to an adjacent oxide or nitride or combination thereof is at least 10:

1.

24. The method of claim 23, wherein said source gas includes a chlorine-comprising gas selected from the group consisting of Cl₂, ICl, BrCl, HCl, BCl₃, CHCl₃, CH₂Cl₂, CCl₄, C₂H₃Cl₃, C₂H₄Cl₂, SiCl₄, C₂H₂Br₂Cl₂, CCl₂O, CCl₃NO₂, and combinations thereof.

25. The method of claim 23, wherein said source gas includes an oxygen-comprising gas selected from the group consisting of O₂, CO, CO₂, CH₄O, C₂H₆O, N₂O, NO₂, O₃, H₂O, and combinations thereof.

26. The method of claim 23, or claim 24, or claim 25, wherein an additive is used in combination with said non-fluorine-containing source gas comprising oxygen and chlorine, and wherein said additive is less than about 15 volumetric percent of the total plasma source gas supply.

27. The method of claim 26, wherein said additive is selected from the group consisting of N₂;

H₂;

C_xH_y;

CF₄;

NF₃; and

combinations thereof, where x is less than about 3 and y is less than about 8.

28. The method of claim 26, wherein said additive is selected from the group consisting of N₂, H₂, C_xH_y, CF₄, NF₃, helium, neon, argon, krypton, xenon, and combinations thereof, wherein x is less than about 3, and y is less than about 8.

29. The method of claim 23, wherein said low k dielectric material is a polymer-based material.

30. The method of claim 29, wherein said polymer-based material is an organic-based material.

31. The method of claim 23, wherein an atomic ratio of said chlorine to said oxygen in said source gas ranges from about 1:

20 to about 20;

1.

32. The method of claim 31, wherein said atomic ratio of said chlorine to said oxygen ranges from about 1:

10 to about 5;

1.