Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Reexamination Certificate
2002-05-31
2003-11-25
Sheehan, John (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
C148S577000
Reexamination Certificate
active
06652668
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of high-purity cobalt and nickel sputter targets. In particular, this invention relates to low-permeability cobalt and nickel sputter targets.
BACKGROUND OF THE INVENTION
In recent years, manufacturers have relied upon several processing techniques to manufacture sputter targets from pure cobalt and pure nickel. Manufacturers have traditionally relied upon a combination of hot working and cold working to lower sputter targets' permeability and increase its magnetic pass through flux (PTF). Unfortunately, these processes have limited success with respect to controlling the high-purity target's final magnetic properties. The target's high magnetic permeability and low PTF in turn limit the target's useful thickness to a relatively thin cross section. Furthermore, because the performance of a ferromagnetic sputter target is extremely sensitive to minor variations in magnetic properties, production of a critically-uniform ferromagnetic target is also challenging. Finally, the magnetic properties of a ferromagnetic sputter target are themselves a means to an end—the ultimate measure of improvement is the performance of the target in a sputtering system.
Kano et al., in EP 799905, recognized that strain can manipulate a high-purity cobalt target's permeability. This patent publication discloses a process that relies upon either cold or warm rolling to reduce the target's initial permeability parallel to the target's surface to about 7. Unfortunately, this process also increases the permeability perpendicular to the target's surface.
Snowman et al., in U.S. Pat. No. 6,176,944, disclose another process for reducing permeability of high-purity cobalt targets. This process relies upon: i) controlled cooling to produce an hcp structure; ii) hot working; iii) further controlled cooling to reproduce the hcp structure; and iv) cold working to lower the target's permeability. This process lowers the target's initial permeability to less than 9. The cobalt targets produced by this process, however, do not suffer from the severe anisotropic magnetic permeability of the Kano et al. process.
Lo et al., in U.S. Pat. No. 5,766,380, entitled “Method for Fabricating Randomly Oriented Aluminum Alloy Sputtering Targets with Fine Grains and Fine Precipitates” disclose a cryogenic method for fabricating aluminum alloy sputter targets. This method uses cryogenic processing with a final annealing step to recrystallize the grains into a desired texture. Similarly, Y. Liu, in U.S. Pat. No. 5,993,621, uses cryogenic working and annealing to manipulate and enhance crystallographic texture of titanium sputter targets.
Sawada et al., in Japan Pat. Pub. No. 3-115,562, disclose a cryogenic process for lowering the permeability of cobalt alloy targets. These cobalt alloy targets contained a combination of fcc and hcp phases. This process used cryogenic working at a temperature of −196° C. to further reduce magnetic permeability of the two phase cobalt alloy target.
Researchers have explored using cryogenic working to increase the forming limits of aluminum alloy sheet panels. For example, Selines et al. disclose a cryogenic process for deforming aluminum sheet in U.S. Pat. No. 4,159,217. This cryogenic process increases elongation and formability at −196° C. In addition, metal sheet forming industries have exploited high strain-hardening rates to extend the forming limits of sheet metal and improve sheet metal strain accommodation uniformity.
SUMMARY OF THE INVENTION
The method manufactures high-purity ferromagnetic sputter targets by cryogenic working the sputter target blank at a temperature below at least −50° C. to impart at least about 5 percent strain into the sputter target blank to increase PTF uniformity of the ferromagnetic target blank. The sputter target blank is a nonferrous metal selected from the group consisting of cobalt and nickel; and the nonferrous metal has a purity of at least about 99.99 weight percent. Finally, fabricating the sputter target blank forms a sputter target having an improved PTF uniformity arising from the cryogenic working.
The method forms a high-purity nonferrous sputter target. The nonferrous sputter target has a sputter source selected from the group consisting of cobalt and nickel. The sputter source has a top surface for sputtering metal atoms onto a substrate, a side edge, a purity of at least about 99.99 weight percent and a uniform PTF. The PTF uniformity is less than about 3 percent of the average PTF for the formula provided in the specification.
REFERENCES:
patent: 4159217 (1979-06-01), Selines et al.
patent: 4643779 (1987-02-01), Abbaschian et al.
patent: 5766380 (1998-06-01), Lo et al.
patent: 5810983 (1998-09-01), Shindo et al.
patent: 5993575 (1999-11-01), Lo et al.
patent: 6056857 (2000-05-01), Hunt et al.
patent: 6176944 (2001-01-01), Snowman et al.
patent: 6197129 (2001-03-01), Zhu et al.
patent: 799905 (1997-10-01), None
patent: 3115562 (1991-05-01), None
Dombrowski David E.
Hunt Thomas J.
Koenigsmann Holger J.
Perry Andrew C.
Praxair S.T. Technology, Inc.
Schwartz Iurie
Sheehan John
LandOfFree
High-purity ferromagnetic sputter targets and method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High-purity ferromagnetic sputter targets and method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High-purity ferromagnetic sputter targets and method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3180266