Halogen-resistant, anodized aluminium for use in semiconductor processing apparatus

• US 20030205479A1
• Filed: 05/03/2002
• Published: 11/06/2003
• Est. Priority Date: 02/08/2002
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Sun, Jennifer Y., Wang, Hong, Stow, Clifford C., Lin, Yixing, Thach, Senh, West, Brian T., Wu, Shun Jackson
• Granted Patent: US 7,033,447 B2
• Time in Patent Office: Days
• US Class Current: 205/153
• CPC Class Codes: C22C 21/06 with magnesium as the next major constituent
• CPC Class Codes: C25D 11/04 of aluminium or alloys based thereon
• CPC Class Codes: C25D 11/045 for forming AAO templates
• CPC Class Codes: C25D 11/06 characterised by the electrolytes used
• CPC Class Codes: C25D 11/16 Pretreatment , e.g. desmutting

Abstract

We have discovered that the formation of particulate inclusions at the surface of an aluminum alloy article, which inclusions interfere with a smooth transition from the alloy surface to an overlying aluminum oxide protective film, can be controlled by maintaining the content of mobile and nonmobile impurities within a specific range and controlling the particulate size and distribution of the mobile and nonmobile impurities and compounds thereof; by heat-treating the aluminum alloy at a temperature less than about 330° C.; and by creating the aluminum oxide protective film by employing a particular electrolytic process. When these factors are taken into consideration, an improved aluminum oxide protective film is obtained.

Claims

1. A high purity aluminum alloy with controlled particulate size and distribution of mobile and nonmobile impurities present in said alloy, said high purity aluminum alloy being employed in the manufacture of semiconductor processing apparatus where exposure to corrosive environments would degrade an aluminum alloy which does not exhibit controlled mobile and nonmobile impurity particulate size and distribution, said high purity aluminum alloy having mobile and nonmobile impurity particulates within specific limits, so that at least 95% of all particles are 5 μ

m or less in size, no more than 5% of said particles range between 20 μ

m and 5 μ

m, and no more than 0.2% of said particles range between 50 μ

m and 20 μ

m.

2. A high purity aluminum alloy in accordance with claim 1, wherein no more than 0.1% of said particles range between 50 μ

m and 20 μ

m.

3. A high purity aluminum alloy in accordance with claim 2, wherein no more than 0.1% of said particles range between 40 μ

m and 20 μ

m.

4. A high purity aluminum alloy in accordance with claim 1, wherein no more than 0.2% of said particles range between 40 μ

m and 20 μ

m.

5. A high purity aluminum alloy in accordance with claim 1, or claim 2, or claim 3, or claim 4, wherein said particulates are formed from mobile and nonmobile impurities selected from the group consisting of magnesium, silicon, iron, copper, manganese, zinc, chromium, titanium, and compounds thereof.

6. A high purity aluminum alloy in accordance with claim 1, wherein said alloy includes mobile and nonmobile impurities present at the following concentrations or at lower concentrations, magnesium at 4.0 weight %, silicon at 0.03 weight %, iron at 0.03 weight %, copper at 0.07 weight %, manganese at 0.015 weight %, zinc at 0.16 weight %, chromium at 0.07 weight %, titanium at 0.05 weight %, and wherein a total of other impurities present in said aluminum alloy ranges from 0-0.1 weight %, with individual other impurities limited to 0-0.03 weight % each.

7. A high purity aluminum alloy in accordance with claim 6, wherein said magnesium is present at a concentration ranging between about 3.5 weight % and about 4.0 weight %.

8. A high purity alumninum alloy in accordance with claim 6, wherein said titanium is present at a concentration of 0.02 weight % or less.

9. A high purity aluminum alloy in accordance with claim 8, wherein said titanium is present at a concentration of 0.01 weight % or less.

10. A method of producing a corrosion-resistant article for use in semiconductor processing apparatus, wherein said article comprises a body formed from high purity aluminum alloy, and wherein at least a surface of said body which is to be exposed to a corrosive environment is covered with an aluminum-oxide-comprising film, and wherein at least said surface of said body which is covered with said aluminum-oxide-comprising film is an aluminum alloy having mobile and nonmobile impurity particulates controlled within limits so that at least 95% of all particles are 5 μ

m or less in size, no more than 5% of said particles range between 20 μ

m and 5 μ

m, and no more than 0.2% of said particles range between 50 μ

m and 20 μ

m.

11. A method in accordance with claim 10, wherein no more than 0.1% of said particles range between 50 μ

m and 20 μ

m.

12. A method in accordance with claim 11, wherein no more than 0.1% of said particles range between 40 μ

m and 20 μ

m.

13. A method in accordance with claim 12, wherein no more than 0.2% of said particles range between 40 μ

m and 20 μ

m.

14. A method in accordance with claim 10, wherein said particulates are formed from mobile and nonmobile impurities selected from the group consisting of magnesium, silicon, iron, copper, manganese, zinc, chromium, titanium, and compounds thereof.

15. A method in accordance with claim 10, wherein at least a portion of said aluminum alloy body of said article comprises mobile and nonmobile impurities present at the following concentrations or at lower concentrations, magnesium at 4.0 weight %, silicon at 0.03 weight %, iron at 0.03 weight %, copper at 0.07 weight %, manganese at 0.015 weight %, zinc at 0.16 weight %, chromium at 0.07 weight %, titanium at 0.05 weight %, and wherein a total of other impurities present in said aluminum alloy ranges from 0-0.1 weight %, with individual other impurities limited to 0-0.03 weight % each.

16. A method in accordance with claim 15, wherein said magnesium is present at a concentration ranging between about 3.5 weight % and about 4.0 weight %.

17. A method in accordance with claim 15, wherein said titanium is present at a concentration of 0.02 weight % or less.

18. A method in accordance with claim 17, wherein said titanium is present at a concentration of 0.01 weight % or less.

19. A method in accordance with claim 10, or claim 12, or claim 15, or claim 16, or claim 17, or claim 18, wherein said corrosion resistance is with respect to active halogen-containing species.

20. A method in accordance with claim 19, wherein said active halogen-containing species are present in the form of a plasma.

21. A method of creating an aluminum oxide protective film on the surface of a high purity aluminum alloy, comprising:

exposing said surface of said aluminum alloy to an electrolytic oxidation process during which said surface is immersed as an anode in an acid electrolyte, with a cathode comprised of an aluminum alloy, and wherein a DC current is applied, wherein said acid electrolyte is a water-based solution comprising 10% to 20% by weight sulfuric acid and about 0.5% to 3.0% by weight oxalic acid, wherein said protective film is created at a temperature ranging from about 5°

C. to about 25°

C., and wherein an applied current density of said DC current ranges from 5 A/ft² to 36 A/ft².

22. A method according to claim 21, wherein, prior to exposing said aluminum alloy surface to said electrolytic oxidation process, said surface is cleaned by contacting said surface with an acidic solution which includes about 60% to 90% by weight of technical grade phosphoric acid having a specific gravity of about 1.7, and about 1%-3% by weight of nitric acid, wherein said cleaning is carried out with said aluminum alloy surface at a temperature in the range of about 100°

C., for a time period ranging from about 30 seconds to about 120 seconds.

23. A method in accordance with claim 22, wherein subsequent to said cleaning of said aluminum alloy surface and prior to said electrolytic oxidation process, said surface is rinsed with a deionized water rinse.

24. A method in accordance with claim 21, or claim 22, or claim 23, wherein said aluminum oxide protective film exhibits hexagonal cells having internal pores ranging in size from about 300 Å

to about 750 Å

in diameter.

25. A method in accordance with claim 21, or claim 22, or claim 23, wherein mobile and nonmobile impurity particulates present in said high purity aluminum alloy are limited so that at least 95% of all particles have a particle size of less than 5 μ

m, no more than 5% of said particles have a particle size ranging between 20 μ

m and 5 μ

m, and no more than 0.2% of said particles have a particle size ranging between 50 μ

m and 20 μ

m.

26. A method in accordance with claim 21, or claim 22, or claim 23, wherein said high purity aluminum alloy comprises mobile and nonmobile impurities present at the following concentrations or at lower concentrations, magnesium at 4.0 weight %, silicon at 0.03 weight %, iron at 0.03 weight %, copper at 0.07 weight %, manganese at 0.015 weight %, zinc at 0.16 weight %, chromium at 0.07 weight %, titanium at 0.05 weight %, and wherein a total of other impurities present in said aluminum alloy ranges from 0-0.1 weight %, with individual other impurities limited to 0-0.03 weight % each.

27. A method in accordance with claim 26, wherein said titanium is present at a concentration of 0.02 weight % or less.

28. A method in accordance with claim 27, wherein said titanium is present at a concentration of 0.01 weight % or less.

29. A method in accordance with claim 25, wherein said high purity aluminum alloy comprises mobile and nonmobile impurities present at the following concentrations or at lower concentrations, magnesium at 4.0 weight %, silicon at 0.03 weight %, iron at 0.03 weight %, copper at 0.07 weight %, manganese at 0.015 weight %, zinc at 0.16 weight %, chromium at 0.07 weight %, titanium at 0.05 weight %, and wherein a total of other impurities present in said aluminum alloy ranges from 0-0.1 weight %, with individual other impurities limited to 0-0.03 weight % each.

30. A method in accordance with claim 29, wherein said titanium is present at a concentration of 0.02 weight % or less.

31. A method in accordance with claim 30, wherein said titanium is present at a concentration of 0.01 weight % or less.

32. A method in accordance with claim 21, wherein, prior to creating said aluminum oxide protective film on said high purity aluminum alloy surface, said aluminum alloy is heat-treated to relieve stress, wherein said heat treatment is carried out at a temperature of 330°

C. or at a lower temperature.

33. A method in accordance with claim 22 or claim 23, wherein, prior to creating said aluminum oxide protective film on said high purity aluminum alloy surface, said aluminum alloy is heat-treated to relieve stress, wherein said heat treatment is carried out at a temperature of 330°

C. or at a lower temperature.

34. A method in accordance with claim 25, wherein, prior to creating said aluminum oxide protective film on said high purity aluminum alloy surface, said aluminum alloy is heat-treated to relieve stress, wherein said heat treatment is carried out at a temperature of 330°

C. or at a lower temperature.

35. A method in accordance with claim 29, wherein, prior to creating said aluminum oxide protective film on said high purity aluminum alloy surface, said aluminum alloy is heat-treated to relieve stress, wherein said heat treatment is carried out at a temperature of 330°

C. or at a lower temperature.