Method of making low magnetic permeability cobalt sputter targets

• US 6,176,944 B1
• Filed: 11/01/1999
• Issued: 01/23/2001
• Est. Priority Date: 11/01/1999
• Status: Expired due to Term

• Current Assignee: Praxair S.T. Technology, Inc. (Linde Plc)
• Original Assignee: Praxair S.T. Technology, Inc. (Linde Plc)
• Inventors: Koenigsmann, Holger, Desert, Andre, Hunt, Thomas J., Snowman, Alfred
• Primary Examiner(s): DIAMOND, ALAN D
• Application Number:
  US09/430,988
• Time in Patent Office: 449 Days
• Field of Search: 204/298.13, 204/298.12, 204/192.2, 148/120, 148/121, 148/122, 148/510, 148/508, 148/509, 148/511, 148/538, 148/557, 148/674, 148/425, 148/DIG.158, 164/459
• US Class Current: 148/121
• CPC Class Codes: C22F 1/10 of nickel or cobalt or alloys based thereon
• CPC Class Codes: C23C 14/3414 Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
• CPC Class Codes: H01F 41/183 Sputtering targets therefor
• CPC Class Codes: Y10S 148/158 Sputtering

Abstract

The present invention provides a high purity cobalt sputter target having a single phase h.c.p. structure and a magnetic permeability less than the intrinsic magnetic permeability of the material. Substantially pure cobalt is cast and slowly cooled, such as at a rate of 15° C./min. Or less, to form a cast target of single phase h.c.p. crystallographic structure. This cast target is hot worked at a temperature of at least about 1000° C. to impart a strain of about 65% or greater into the cobalt material, followed by a slow, controlled cooling to room temperature, such as at a rate of 15° C./min. or less, to maintain the single phase h.c.p. crystallographic structure. The cooled target is then cold worked at substantially room temperature to impart a strain of about 5-20%. The sputter target of the present invention processed by this method has a magnetic permeability of less than about 9, grain sizes in the size range of about 70-160 μm, and average grain size of about 130 μm.

Claims

1. A method for manufacturing low magnetic permeability cobalt sputter targets, comprising the steps of:

casting a substantially pure cobalt metal having an intrinsic magnetic permeability and slowly cooling the metal at a controlled rate to form a substantially pure cobalt sputter target having a single hexagonal close packed phase;

hot working the sputter target at a temperature of at least about 1000°

C. to a strain of at least about 65%;

slowly cooling the hot worked sputter target at a controlled rate to maintain the single hexagonal close packed phase; and

cold working the hot worked sputter target at substantially room temperature to a strain of about 5% to about 20%,

wherein the cold worked sputter target has a magnetic permeability less than the intrinsic magnetic permeability.

2. The method of claim 1, wherein the cast metal is cooled at a controlled rate of no greater than about 15°

C./main to form the sputter target.

3. The method of claim 1, wherein the hot worked sputter target is cooled at a controlled rate of no greater than about 15°

C./min.

4. The method of claim 1, wherein the cold worked sputter target has a magnetic permeability of less than about 9.

5. The method of claim 1, wherein the cold worked sputter target comprises grains in the size range of about 70 μ

m to about 160 μ

m.

6. The method of claim 1, wherein the cold worked sputter target comprises grains having an average size of about 130 μ

m.

7. The method of claim 1, wherein the cobalt metal has a purity of at least about 99.99%, by weight.

8. The method of claim 1, wherein the hot worked target is cold worked to a strain of about 10%.

9. A method for manufacturing low magnetic permeability cobalt sputter targets, comprising the steps of:

casting a substantially pure cobalt metal having an intrinsic magnetic permeability and cooling the metal at a controlled rate of no greater than about 15°

C./min. to form a substantially pure cobalt sputter target having a single hexagonal close packed phase;

hot working the sputter target at a temperature of at least about 1000°

C. to a strain of at least about 65%;

cooling the hot worked sputter target at a controlled rate of no greater than about 15°

C./min. to maintain the single hexagonal close packed phase; and

cold working the hot worked sputter target at substantially room temperature to a strain of about 5% to about 20%,

wherein the cold worked sputter target has a magnetic permeability less than the intrinsic magnetic permeability.

10. The method of claim 9, wherein the cold worked sputter target has a magnetic permeability of less than about 9.

11. The method of claim 9, wherein the cold worked sputter target comprises grains in the size range of about 70 μ

m to about 160 μ

m.

12. The method of claim 9, wherein the cold worked sputter target comprises grains having an average size of about 130 μ

m.

13. The method of claim 9, wherein the cobalt metal has a purity of at least about 99.99%, by weight.

14. The method of claim 9, wherein the hot worked target is cold worked to a strain of about 10%.