Coating boron carbide on aluminum

• US 6,808,747 B1
• Filed: 01/21/2000
• Issued: 10/26/2004
• Est. Priority Date: 12/19/1996
• Status: Expired due to Fees

• Current Assignee: Hong Shih, Nianci Han
• Original Assignee: Hong Shih, Nianci Han
• Inventors: Shih, Hong, Han, Nianci
• Primary Examiner(s): Lund, Jeffrie R
• Assistant Examiner(s): Zervigon, Rudy
• Application Number:
  US09/489,356
• Time in Patent Office: 1,740 Days
• Field of Search: 427/450, 427/454, 101/453, 101/458, 101/463.1, 156/155, 156/345.1, 428/217, 428/615
• US Class Current: 427/249.5
• CPC Class Codes: C23C 28/044 coatings specially adapted for cutting tools or wear applications
• CPC Class Codes: H01J 37/32495 Means for protecting the vessel against plasma
• CPC Class Codes: Y10S 156/914 Differential etching apparatus including particular materials of construction

Abstract

A method of depositing boron carbide on an aluminum substrate, particularly useful for a plasma etch reactor having interior surfaces facing the plasma composed of boron carbide, preferably principally composed of B₄C. Although in this application, the boron carbide may be a bulk sintered body, in the method of the invention it may be a layer of boron carbide coated on an aluminum chamber part. The boron carbide coating may be applied by thermal spraying, such as plasma spraying, by chemical vapor deposition, or by other layer forming technique such as a surface converting reaction. The boron carbide is highly resistant to high-density plasma etchants such as BCl₃. The plasma sprayed coating is advantageously applied to only a portion of an anodized aluminum wall. The boron carbide may be sprayed over the exposed portion of an aluminum substrate over which the anodization has been removed. A band of the aluminum substrate at the transition between the anodization and the boron carbide is roughened prior to anodization so that the boron carbide sticks to the correspondingly roughened surface of the anodization. Alternatively, the entire wall area of the anodized aluminum to be coated is roughened, and the boron carbide is sprayed over the anodization.

Claims

1. A method of forming a boron carbide layer on an aluminum-based substrate, comprising:

an initial step of anodizing a surface of an aluminum-based substrate to form an anodization layer;

then removing said anodization layer from a first portion of said substrate separated by a predetermined boundary from a second portion of said substrate from which said anodization layer is not removed; and

then depositing a boron carbide layer upon said anodization layer, wherein said depositing step deposits said boron carbide layer in a layer extending over said first portion of said substrate and across said boundary to a neighboring part of said second portion of said substrate.

2. A method of forming a boron carbide layer on an aluminum-based substrate, comprising:

an initial step of roughening at least a first portion of a surface of an aluminum-based substrate;

anodizing said surface of said aluminum-based substrate to form an anodization layer, wherein said anodizing step anodizes said first portion;

removing said anodization layer from a second portion of said substrate adjacent to said first portion and separated therefrom by a predetermined boundary, said roughened first portion extending below a portion of said anodization left by said removing step; and

then depositing a boron carbide layer upon said anodization layer, wherein said depositing step deposits said boron carbide layer on said anodization layer overlying said anodized first portion.

3. The method of claim 2, wherein a material of said substrate is selected from the group consisting of aluminum and aluminum alloys.

4. The method of claim 2, wherein said boron carbide layer comprises B₄C.

5. The method of claim 2, wherein said boron carbide layer comprises particles of B₄C.

6. The method of claim 2, wherein said boron carbide layer comprises a composition between B₄C and B₁₃C₃.

7. The method of claim 2, wherein said boron carbide layer comprises between 14 to 30 wt % of carbon relative to a total weight of carbon and boron.

8. The structure of claim 7, wherein said boron carbide layer comprises between 18 to 25 wt % of carbon relative to a total weight of carbon and boron.

9. The process of claim 2, wherein said boron carbide layer is deposited onto said anodized first portion and second portion of said substrate.

10. A method of coating boron carbide on an aluminum-based substrate, comprising the steps of:

roughening a surface of a substrate to a value of surface finish R_a of at least 2.5 μ

m, wherein said substrate is composed of an aluminum-based material selected from the group consisting of substantially pure aluminum and aluminum alloys including at least 90 wt % elemental aluminum;

anodizing said substrate to form an anodization layer;

removing said anodization layer from only a first portion and not from a second portion of said surface of said substrate; and

depositing a boron carbide layer upon said anodization layer, wherein said boron carbide layer is deposited on both said fist and second portions after said removing step.

11. The method of claim 10, wherein said depositing step comprises thermal spraying to form said boron carbide layer upon said surface.

12. The method of claim 10, wherein said depositing step comprises chemical vapor deposition.

13. The method of claim 10, wherein said boron carbide layer comprises B₄C.

14. The method of claim 10, wherein said boron carbide layer comprises particles of B₄C.

15. The method of claim 10, wherein said boron carbide layer comprises a composition between B₄C and B₁₃C₃.

16. The method of claim 10, wherein said boron carbide layer comprises between 14 to 30 wt % of carbon relative to a total weight of carbon and boron.

17. The structure of claim 16, wherein said boron carbide layer comprises between 18 to 25 wt % of carbon relative to a total weight of carbon and boron.

18. The structure of claim 10, wherein said roughening step is performed before said anodizing step.

19. The method of claim 10, wherein said surface finish R_a is no more than 7.6 μ

m.

20. The method of claim 19, wherein said first and second parts are only partially co-extensive.

21. The method of claim 19, wherein said anodization layer contacts roughened and unroughened portions of said surface and said boron carbide layer contacts other roughened and unroughened portions of said surface.

22. The method of claim 21, wherein said boron carbide layer only partially covers said anodization layer.