Stock material or miscellaneous articles – All metal or with adjacent metals – Laterally noncoextensive components
Patent
1989-08-09
1991-09-17
Dean, R.
Stock material or miscellaneous articles
All metal or with adjacent metals
Laterally noncoextensive components
75232, 75234, 505 1, 505700, 505731, 505785, C22C 3200
Patent
active
050494520
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a target member used for formation of a superconducting film on a surface of a substrate by using, for example, a sputtering technique, and, more particularly, to a target member having a high cooling efficiency and a low resistivity and further superior in mechanical strength.
BACKGROUND ART
Recently, many attempts are made for forming a film of a superconducting ceramic material mainly composed of an oxide containing a rare earth metal such as, for example, yttrium an alkaline earth metal and copper (which is hereinbelow referred to as "oxide in the R-A-Cu-O system") on a surface of a substrate. One of these attempts is to form a superconducting ceramic in the R-A-Cu-0 system by sputtering a target, and description is made for a fabrication process of the target used in the sputtering process.
Conventionally, the fabrication process of the target used for formation of a superconducting film starts with preparing a powder of an oxide containing a rare earth metal such as, for example, yttrium, a powder of an alkaline earth metal carbonate and a powder of a copper oxide, and these ingredient powders are 10 microns in average diameter of the component particles. Those powders are mixed into a predetermined proportion to form a mixture, and the mixture is calcined in an oxidation ambient at 850 degrees to 950 degrees in centigrade, the calcined product is, then, pulverized, and the calcining and the pulverizing are repeated twice or more, if necessary, so as to produce a powder of a superconducting ceramic material in the R-A-Cu-0 system
The powder of the superconducting ceramic material is shaped by using a hot pressing technique. Namely, the powder of the superconducting ceramic material is heated in a vacuum ambient at 800 degrees to 900 degrees in centigrade and pressed at 100 kgf/cm.sup.2 to 200 kgf/cm.sup.2 for 1 to 4 hours. The target is fabricated in this manner.
The target thus fabricated is mainly formed of a superconducting ceramic material in the R-A-Cu-0 system or of a substance like the ceramic in the R-A-Cu-0 system containing the copper oxide (which is hereinbelow represented by CuO) equal to or less than 20% by volume.
However, the composition of the target may be transferred to the composition of the thin film depending upon the sputtering system and the sputtering conditions, and the target is liable to be causative of shortage of CuO. For this reason, the powder of the superconductor used in the formation of the prior art target contains excessive CuO equal to or less than 20% by volume.
However, the prior art target exhibits low in thermal conductivity, and, accordingly, is low in cooling efficiency. For this reason, a large difference in temperature exists between the sputtered front surface and the cooled back surface of the target, and a problem is encountered in the target in production of cracks due to the thermal stress. Moreover, the prior art target is so large in electric resistivity that an inexpensive DC diode sputtering system can not be used, and, for this reason, an expensive RF sputtering system is usually required This results in another problem in a large amount of production cost for the production of the superconducting thin film. Furthermore, the prior art target exhibits low mechanical strength and brittleness, so in careful handling is required.
It is therefore an object of the present invention to provide a target which is free from the problems inherent in the prior art target.
DISCLOSURE OF INVENTION
Research and development efforts have been made by the inventors for providing a solution of the problems inherent in the prior art target used for the formation of the superconducting film. The inventors discovers that a target solves the aforementioned problems when the target is produced by mixing a powder of metallic copper ranging between about 8% and about 40% by volume with an oxide in the R-A-Cu-O system or an oxide containing a rare earth metal and an alkaline earth metal or metals, (this oxide is hereinbelow
REFERENCES:
Ohkuma et al., "Preparation of Y-Ba-Cu-O Thin Films by Rf-Magnetron Sputtering" Jap. J. Appl. Phys. vol. 26, No. 9, Sep., 1987, pp. L1484-L1486.
Goyal et al. "Cermets of the Y.sub.1 Ba.sub.2 Cu.sub.3 O.sub.7-.delta. Superconductors" Materials Letters, vol. 6, No. 8.9, May 1988, pp. 257-260.
Komuro et al., "Structure and Superconducting Properties of Y-Ba-Cu-O Sputtered Films", Jap. J. of Appl. Phys., vol. 26, No. 11, Nov. 1987, pp. L1907-L1909.
Sugihara Tadashi
Takeshita Takuo
Dean R.
Mitsubishi Metal Corporation
Schumaker David
LandOfFree
Target member used for formation of superconducting film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Target member used for formation of superconducting film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Target member used for formation of superconducting film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1916505