Method of etching a high aspect ratio contact

• US 8,614,151 B2
• Filed: 01/04/2008
• Issued: 12/24/2013
• Est. Priority Date: 01/04/2008
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Benson, Russell A., Taylor, Ted, Kiehlbauch, Mark
• Primary Examiner(s): Ahmed, Shamim
• Application Number:
  US11/969,443
• Publication Number:
  US 20090176375A1
• Time in Patent Office: 2,181 Days
• Field of Search: 216/41, 216/67, 438/710, 438/720
• US Class Current: 438/720
• CPC Class Codes: C09K 13/00 Etching, surface-brightening or pickling compositions for glass C03C15/00, C03C25/66; for mortars, concrete, artificial or natural stone or ceramics C04B41/5338 ; for metallic material C23F, C23G1/00, C25F1/00; for semi-conductors H01L
• CPC Class Codes: H01L 21/31116 by dry-etching

Abstract

Methods and an etch gas composition for etching a contact opening in a dielectric layer are provided. Embodiments of the method use a plasma generated from an etch gas composed of C₄F₈ and/or C₄F₆, an oxygen source, and a carrier gas in combination with tetrafluoroethane (C₂F₄) or a halofluorocarbon analogue of C₂F₄.

Claims

1. A method of etching an opening in a dielectric layer, comprising:

forming a plasma etching gas from C₄F₆, C₄F₈ or a mixture of C₄F₆ and C₄F₈, an oxygen source gas, an inert gas, and C₂F₄; and

etching the opening through the dielectric layer to an underlying substrate with the plasma etching gas while depositing polymer material to form and maintain a conformal polymer layer at a thickness effective to continually passivate sidewalls of the opening during the etching;

wherein after the etching, the conformal polymer layer remains over the sidewalls.

2. The method of claim 1, wherein the plasma etching gas comprises C₄F₆:

C₂F₄, C₄F₈;

C₂F₄, or C₄F₈ and C₄F₆;

C₂F₄ at a ratio of about 0.25-1.5;

1.

3. The method of claim 1, wherein the dielectric layer comprises an oxide.

4. The method of claim 1, wherein the dielectric layer comprises silicon nitride and the plasma etching gas further comprises a hydrofluorocarbon having the general formula C_xH_yF_z where x=1-6, y=1-6 and z=1-6, or a combination thereof.

5. The method of claim 1, wherein the opening is a contact hole or a trench having an aspect ratio of about 20-30:

1.

6. The method of claim 1, wherein the conformal polymer layer on the sidewalls of the opening has a thickness of about 5-20 Å

for the depth profile of the opening.

7. The method of claim 1, wherein the dielectric is etched at rate of about 3000-6000 Å

/minute.

8. The method of claim 1, wherein the plasma etching gas consists essentially of the gases.

9. The method of claim 1, wherein forming the plasma etching gas comprises flowing the gases at a flow rate of about 10-100 sccm for C₄F₆ or C₄F₈ and at about 50-150 sccm for C₂F₄.

10. The method of claim 1, wherein forming the plasma etch gas comprises flowing C₄F₆ and C₄F₈ at a combined flow rate of about 30-100 sccm, and C₂F₄ at a flow rate of about 50-150 sccm.

25. The method of claim 1, further comprising, after the etching, removing the conformal polymer layer.

26. The method of claim 25, wherein the removing is conducted by a dry etch process.

27. The method of claim 26, wherein the dry etch process comprises an oxygen plasma ashing step.

28. The method of claim 25, wherein the removing is conducted by a wet etch process.

11. A method of etching an opening in a dielectric layer, comprising:

forming plasma etching gas from C₄F₆, C₄F₈ or a mixture thereof at a flow rate of about 50-70 sccm, an oxygen source gas at a flow rate of about 20-40 sccm, an inert diluent gas at a flow rate of about 900-1300 sccm, and C₂F₄ at a flow rate of about 80-100 sccm; and

etching the opening through the dielectric layer to an underlying substrate with the plasma etching gas while depositing polymer material during the etching to form and maintain a conformal polymer layer at a thickness effective to continually passivate sidewalls of the opening during the etching;

wherein after the etching, the conformal polymer layer remains over the sidewalls.

12. A method of etching an opening in a dielectric layer comprising:

applying a plasma etching gas to etch the dielectric layer to an underlying substrate, the plasma etching gas formed from C₄F₆, C₄F₈ or mixture thereof, an oxygen source gas, an inert diluent gas, and a halofluorocarbon selected from the group consisting of C₂F₄Br₂, C₂F₄I₂ and CF₂I₂;

wherein a polymer material is deposited during the etching to form and maintain a conformal polymer layer at a thickness effective to continually passivate sidewalls of the opening during etching, and after the etching, the conformal polymer layer remains over the sidewalls.

13. The method of claim 12, wherein the plasma etching gas is formed by flowing in C₄F₆, C₄F₈ or a mixture thereof at a flow rate of about 10-100 sccm and the halofluorocarbon at a rate of about 50-300 sccm.

14. The method of claim 13, wherein the plasma etching gas is formed by flowing in C₂F₄Br₂ or C₂F₄I₂ at a rate of about 50-150 sccm, or CF₂I₂ at a rate of about 100-300 sccm.

15. The method claim 12, wherein the plasma etching gas comprises C₄F₆:

halofluorocarbon, C₄F₈;

halofluorocarbon or C₄F₈ and C₄F₆;

halocarbon at a ratio of about 0.25-1.5;

1.

16. The method of claim 12, wherein the plasma etching gas further comprises an additional fluorocarbon gas having the general formula C_xF_y where x=1-6 and y=2-8.

17. The method of claim 12, wherein the dielectric layer comprises silicon nitride, and the plasma etching gas further comprises a hydrofluorocarbon gas having the general formula C_xH_yF_z where x=1-6, y=1-6, and z=1-6, or a mixture thereof.

18. The method Claim of 12, wherein the plasma etching gas further comprises a hydrofluorocarbon gas having the general formula C_xH_yF_z where x=1-6, y=1-6 and z=1-6.

19. A method of etching an opening in a dielectric layer, comprising:

applying a plasma etching gas comprising at least one of C₄F₆ and C₄F₈, an oxygen source gas, an inert diluent gas, and C₂F₄, in amounts effective to form a plasma etching gas to etch the opening through the dielectric layer while depositing a polymer material to form and maintain a conformal polymer layer on sidewalls of the opening at a thickness effective to continually passivate the sidewalls during the etching, wherein after the etching, the conformal polymer layer remains over the sidewalls.

20. The method of claim 19, wherein the etching gas further comprises an additional fluorocarbon gas having the general formula C_xF_y where x=1-6 and y=2-8.

21. The method of claim 19, wherein the etching gas further comprises a hydrofluorocarbon gas having the general formula C_xH_yF_z where x=1-6, y=1-6 and z=1-6, or a mixture thereof.

22. The method of claim 19, wherein the etching gas consists essentially of the gases.

23. A method of etching an opening in a dielectric layer, comprising:

applying a plasma etching gas consisting essentially of at least one of C₄F₆ and C₄F₈, an oxygen source gas, an inert diluent gas, and a halofluorocarbon selected from the group consisting of C₂F₄Br₂, C₂F₄I₂ and CF₂I₂, in amounts effective to etch the opening through the dielectric layer while depositing a polymer material to form and maintain a conformal polymer layer on sidewalls of the opening at a thickness effective to continually passivate the sidewalls during the etching, wherein after the etching, the conformal polymer layer remains over the sidewalls.

24. A method of etching an opening in a dielectric layer, comprising:

applying a plasma etching gas consisting essentially of at least one of C₄F₆ and C₄F₈, an oxygen source gas, an inert diluent gas, a halofluorocarbon selected from the group consisting of C₂F₄Br₂, C₂F₄I₂ and CF₂I₂, and at least one of an additional fluorocarbon gas having the general formula C_x F_y where x=1-6 and y=2-8 and a hydrofluorocarbon gas having the general formula C_xH_yF_z where x=1-6, y=1-6 and z=1-6,

said gases in amounts effective to etch the opening through the dielectric layer while depositing a polymer material to form and maintain a conformal polymer layer on sidewalls of the opening at a thickness effective to continually passivate the sidewalls during the etching, wherein the conformal polymer layer remains over the sidewalls after the etching.