Method of making low magnetic permeability cobalt sputter targets
First Claim
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.
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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.
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Citations
14 Claims
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1. A method for manufacturing low magnetic permeability cobalt sputter targets, comprising the steps of:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for manufacturing low magnetic permeability cobalt sputter targets, comprising the steps of:
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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. - View Dependent Claims (10, 11, 12, 13, 14)
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Specification