Method of etching an oxide layer

• US 5,468,342 A
• Filed: 04/28/1994
• Issued: 11/21/1995
• Est. Priority Date: 04/28/1994
• Status: Expired due to Term

• Current Assignee: Invensas Corporation
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Nulty, James E., Trammel, Pamela S.
• Primary Examiner(s): POWELL, WILLIAM A
• Application Number:
  US08/234,478
• Time in Patent Office: 572 Days
• Field of Search: 156/643, 156/644, 156/651, 156/657, 156/659.1, 156/661.1, 156/651, 156/904, 156/653, 204/192.32, 204/192.37, 437/238, 437/241, 216/63, 216/67, 216/75
• US Class Current: 438/714
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/31144 using masks
• CPC Class Codes: H01L 21/76816 Aspects relating to the layout of the pattern or to the size of vias or trenches layout of the interconnections per se H01L23/528; CAD of ICs G06F30/00
• CPC Class Codes: Y10S 438/945 Special, e.g. metal

Abstract

A method of etching openings in oxide layers is disclosed. A hard mask layer is formed on the oxide layer. The hard mask layer is then patterned by a photoresist layer and an etch is performed to form openings in the hard mask. Next, the patterning layer may be removed and an etch is performed to remove the oxide in the regions defined by the hard mask layer openings. The etch with hard mask has minimized aspect ratio dependency, so that openings of different sizes may be formed simultaneously. An etch that may be carried out with Freon 134a (C₂ H₂ F₄) to provide superior oxide:nitride selectivity is also disclosed. Additionally, the etch may be carried out at high temperature for improved wall profile without loss of selectivity. For deep openings, a two step etch process is disclosed, with a polymer clean step between the etches to remove polymer build up from first etch, and allow the etch to proceed to an increased depth.

Claims

1. A method of etching an oxide layer comprising the steps of:

providing a substrate having said oxide layer thereon;

depositing a hard mask layer on said oxide layer, wherein said hard mask layer comprises a material selected from the group consisting of silicon nitride, polysilicon, aluminum, a refractory metal, and a refractory metal silicide;

forming a patterning layer on said hard mask layer;

forming a patterning layer opening in said patterning layer to form a hard mask layer exposed region;

forming a hard mask layer opening in said hard mask layer exposed region to form an oxide layer exposed region; and

,

forming an oxide layer opening in said oxide layer exposed region by exposing said oxide layer exposed region to a plasma.

2. The method as described in claim 1 wherein said patterning layer is removed prior to the completion of said step of forming said oxide layer opening.

3. The method as described in claim 1 wherein said patterning layer is removed prior to the beginning of said step of forming said oxide layer opening.

4. The method as described in claim 2 wherein a plurality of said patterning layers openings, said hard mask layer openings and said oxide layer openings are formed, and wherein a first one of said oxide layer openings has a different aspect ratio from a second one of said oxide layer openings.

5. The method as described in claim 1 wherein said substrate is at a temperature of 110°

C. or greater during at least some of said step of forming said oxide layer opening.

6. The method as described in claim 2 wherein said substrate is at a temperature of 110°

C. or greater during at least some of said step of forming said oxide layer opening.

7. The method as described in claim 3 wherein said substrate is at a temperature of 110°

C. or greater during at least some of said step of forming said oxide layer opening.

8. The method as described in claim 1 wherein said substrate is at a temperature of 130°

C. or greater during at least some of said step of forming said oxide layer opening.

9. The method as described in claim 2 wherein said substrate is at a temperature of 130°

C. or greater during at least some of said step of forming said oxide layer opening.

10. The method as described in claim 1 wherein said substrate is at a temperature above a reticulation temperature of said patterning layer during at least some of said step of forming said oxide layer opening.

11. The method as described in claim 2 wherein said substrate is at a temperature above a reticulation temperature of said patterning layer during at least some of said step of forming said oxide layer opening.

12. The method as described in claim 1 wherein said substrate comprises a silicon nitride layer underlying said oxide layer.

13. The method as described in claim 2 wherein said substrate comprises a silicon nitride layer underlying said oxide layer.

14. The method as described in claim 5 wherein said plasma is formed in a flow comprising CH₂ F--CF₃.

15. The method as described in claim 6 wherein said plasma is formed in a flow comprising CH₂ F--CF₃.

16. A method of etching an oxide layer comprising the steps of:

providing a substrate having said oxide layer thereon;

forming a masking layer on said Oxide layer, said masking layer being a low carbon content material;

forming a masking layer opening in said masking layer to form an oxide layer exposed region; and

,

forming an oxide layer opening in said oxide layer exposed region by exposing said oxide layer exposed region to a plasma.

17. The method as described in claim 16 wherein a plurality of said masking layer openings and said oxide layer openings are formed, and wherein a first one of said oxide layer openings has a different aspect ratio from a second one of said oxide layer openings.

18. The method as described in claim 16 wherein said substrate is at a temperature of 110°

C. or greater during at least some of said step of forming said oxide layer opening.

19. The method as described in claim 16 wherein said substrate is at a temperature of 130°

C. or greater during at least some of said step of forming said oxide layer opening.

20. The method as described in claim 16 wherein said plasma is formed in a flow comprising CH₂ F--CF₃.

21. The method as described in claim 18 wherein said plasma is formed in a flow comprising CH₂ F--CF₃.

22. A method of etching an oxide layer comprising the steps of:

providing a substrate having said oxide layer thereon;

forming a masking layer on said oxide layer;

forming a masking layer opening in said masking layer to form an oxide layer exposed region; and

,

forming an oxide layer opening in said oxide layer exposed region by exposing said oxide layer exposed region to a plasma, wherein said masking layer does not have significant carbon interaction with said plasma.

23. The method as described in claim 22 wherein a plurality of said masking layer openings and said oxide layer openings are formed, and wherein a first one of said oxide layer openings has a different aspect ratio from a second one of said oxide layer openings.

24. The method as described in claim 22 wherein said substrate is at a temperature of 110°

C. or greater during at least some of said step of forming said oxide layer opening.

25. The method as described in claim 22 wherein said substrate is at a temperature of 130°

C. or greater during at least some of said step of forming said oxide layer opening.

26. The method as described in claim 22 wherein said plasma is formed in a flow comprising CH₂ F--CF₃.

27. The method as described in claim 24 wherein said plasma is formed in a flow comprising CH₂ F--CF₃.

28. A method of etching an oxide layer comprising the steps of:

providing a substrate having said oxide layer thereon;

exposing a first portion of said oxide layer and covering a second portion of said oxide layer; and

,

forming an oxide layer opening in said first portion by exposing said first portion to a plasma formed in a gas flow comprising CH₂ F--CF₃.

29. The method as described in claim 28 wherein said substrate comprises a silicon nitride layer underlying said oxide layer.

30. The method as described in claim 28 wherein said step of exposing said first portion and covering said second portion of said oxide layer comprises the steps of:

depositing a masking layer on said oxide layer;

forming a patterning layer on said masking layer;

forming a patterning layer opening in said patterning layer corresponding to said first portion; and

,

forming a masking layer opening in said masking layer to expose said first portion.

31. The method as described in claim 29 wherein said step of exposing said first portion and covering said second portion of said oxide layer comprises the steps of:

depositing a masking layer on said oxide layer;

forming a patterning layer on said masking layer;

forming a patterning layer opening in said patterning layer corresponding to said first portion; and

,

forming a masking layer opening in said masking layer to expose said first portion.

32. The method as described in claim 29 wherein said patterning layer is removed prior to the completion of said step of forming said oxide layer opening.

33. The method as described in claim 29 wherein said patterning layer is removed prior to the beginning of-said step of forming said oxide layer opening.

34. The method as described in claim 31 wherein a plurality of said patterning layers openings, said masking layer openings and said oxide layer openings are formed, and wherein a first one of said oxide layer openings has a different aspect ratio from a second one of said oxide layer openings.

35. The method as described in claim 28 wherein said masking layer comprises a material selected from the group consisting of polysilicon, aluminum, a refractory metal, and a refractory metal silicide.

36. The method as described in claim 28 wherein said substrate is at a temperature of 110°

C. or greater during at least some of said step of forming said oxide layer opening.

37. The method as described in claim 28 wherein said substrate is at a temperature of 130°

C. or greater during at least some of said step of forming said oxide layer opening.

38. The method as described in claim 29 wherein said substrate is at a temperature of 110°

C. or greater during at least some of said step of forming said oxide layer opening.

39. The method as described in claim 29 wherein said substrate is at a temperature of 130°

C. or greater during at least some of said step of forming said oxide layer opening.

40. The method as described in claim 31 wherein said substrate is at a temperature of 110°

C. or greater during at least some of said step of forming said oxide layer opening.

41. The method as described in claim 31 wherein said substrate is at a temperature of 130°

C. or greater during at least some of said step of forming said oxide layer opening.

42. The method as described in claim 29 wherein said oxide layer opening exposes a corner of a structure, said corner covered with said nitride layer.

43. The method as described in claim 31 wherein said oxide layer opening exposes a corner of a structure, said corner covered with said nitride layer.

44. The method as described in claim 32 wherein said oxide layer opening exposes a corner of a structure, said corner covered with said nitride layer.

45. The method as described in claim 38 wherein said oxide layer opening exposes a corner of a structure, said corner covered with said nitride layer.

46. The method as described in claim 39 wherein said oxide layer opening exposes a corner of a structure, said corner covered with said nitride layer.

47. The method as described in claim 28 wherein said gas flow further comprises CHF₃.

48. The method as described in claim 29 wherein said gas flow further comprises CHF₃.

49. The method as described in claim 31 wherein said gas flow further comprises CHF₃.

50. The method as described in claim 36 wherein said gas flow further comprises CHF₃.

51. The method as described in claim 38 wherein said gas flow further comprises CHF₃.

52. The method as described in claim 40 wherein said gas flow further comprises CHF₃.

53. A method of etching an oxide layer comprising the steps of:

providing a substrate having said oxide layer thereon;

depositing a masking layer on said oxide layer;

forming a patterning layer on said masking layer;

forming a patterning layer opening in said patterning layer to form a masking layer exposed region;

forming a masking layer opening in said masking layer exposed region to form an oxide layer exposed region;

exposing said oxide layer exposed region to a first plasma;

performing a polymer clean step; and

,

exposing said oxide layer exposed region to a second plasma.

54. The method as described in claim 53 wherein said polymer clean step is performed by exposing said substrate to a plasma formed in a mixture comprising oxygen.

55. The method as described in claim 53 wherein said polymer clean step is performed by exposing said substrate to a mixture comprising H₂ SO₄ and H₂ O₂.

56. The method as described in claim 53 wherein a plurality of said patterning layer openings, said masking layer openings, and said oxide layer openings are formed, and wherein a first one of said oxide layer openings has a different aspect ratio from a second one of said oxide layer openings.

57. The method as described in claim 53 wherein said masking layer comprises a material selected from the group consisting of polysilicon, aluminum, a refractory metal, and a refractory metal silicide.

58. The method as described in claim 53 wherein said substrate is at a temperature of 110°

C. or greater during at least some of said step of forming said oxide layer opening.

59. The method as described in claim 53 wherein said substrate is at a temperature of 130°

C. or greater during at least some of said step of forming said oxide layer opening.

60. The method as described in claim 53 wherein said second plasma is formed in a gas flow comprising CH₂ F--CF₃.

61. The method as described in claim 57 wherein said second plasma is formed in a gas flow comprising CH₂ F--CF₃.

62. The method as described in claim 58 wherein said second plasma is formed in a gas flow comprising CH₂ F--CF₃.

63. The method as described in claim 59 wherein said second plasma is formed in a gas flow comprising CH₂ F--CF₃.