Superconductor technology: apparatus – material – process – High temperature – per se – Having tc greater than or equal to 150 k
Patent
1989-08-18
1991-05-28
Roy, Upendra
Superconductor technology: apparatus, material, process
High temperature , per se
Having tc greater than or equal to 150 k
29599, 427 62, 428633, 428930, 505701, 505702, 505704, 505730, C04B 4189, H01B 1206, H01L 2188
Patent
active
050195549
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a structure of a superconductive wiring and, more particularly, to a structure of a superconductive wiring used for fabricating a thin film integrated circuit, a thick film integrated circuit and so forth.
BACKGROUND ART
An example of the prior art superconductive wiring is shown in FIG. 1. The structure of the wiring is disclosed in the paper entitled as "Technology of Superconductive Wiring on Alumina Substrate", Electronic Parts and Material published by Association of Industrial Investigation, 1987 August, pages 89 to 92.
Referring to FIG. 1, reference numeral 1 designates a high purity alumina substrate, and the high purity alumina substrate is sometimes abbreviated as FGA (Fine Grained Alumina) substrate. On the high purity alumina substrate 1 a thick film wiring 2 is formed. The process of forming the thick film wiring 2 starts with preparation of a powder of yttria represented by the molecular formula of Y.sub.2 O.sub.3, a powder of the barium oxide represented by the molecular formula of BaO and a powder of the copper oxide represented by the molecular formula of CuO. These powders are calcined to produce a bulk solid of a superconductive ceramic material. The bulk solid of the superconductive ceramic material is pulverized to produce a powder of the superconductive ceramic material, and the powder of the superconductive ceramic material is mixed into an organic vehicle, so that a paste is formed. The paste is printed on the high purity alumina substrate 1 by using a screen printing technique, and, thereafter, the high purity alumina substrate is placed in the atmospheric ambient at about 800 degrees to about 1000 degrees in centigrade for sintering, then a thick film wiring strip 2 being formed.
However, a problem is encountered in the quality of the substrate usable. Namely, even if the paste of the superconductive ceramic material is printed on a low purity alumina substrate available in the market and a thick film wiring strip is, then, produced through a process sequence similar to that described above, the thick film wiring strip does not show any superconductivity. This is because of the fact that the low purity alumina substrate available in the market contains a large amount of impurities such as silicon dioxide. It is figured that the impurities react on the paste during the sintering stage and, for this reason, an occurrence of the superconductivity is suppressed in the thick film wiring strip. Such a phenomenon is reported in JAPANESE JOURNAL OF APPLIED PHYSICS, 1987 May, VOL. 26 No. 5, Table 1 in page L761.
It is therefore an object of the present invention to provide a structure of a superconductive wiring feasible for fabrication on a low purity substrate available in the market.
DISCLOSURE OF INVENTION
A structure of a superconductive wiring according to the present invention comprises an insulating layer, a buffer layer formed on the insulating layer, and a wiring pattern having a wiring strip formed of a superconductive ceramic material containing at least one element selected from the group consisting of scandium, yttrium and lanthanides, at least one alkaline earth metal, copper and oxygen, and the buffer layer is formed of a substance hardly reacting on the superconductive ceramic material in a high temperature ambient, in which the substance is represented by the chemical formula SiAlON.
The superconductive ceramic material may contain a plurality of elements selected from the group consisting of scandium, yttrium and lanthanides, a plurality of alkaline earth metals, copper and oxygen.
The aforementioned structure of the superconductive wiring according to the present invention is provided with the buffer layer interposed between the insulating layer and the wiring pattern, and the buffer layer hardly reacts on the superconductive ceramic material in a high temperature ambient. For this reason, when the wiring strip of the superconductive ceramic material is formed on the buffer layer, the wiring strip continues to show the su
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Sugihara Tadashi
Takeshita Takuo
Mitsubishi Metal Corp.
Roy Upendra
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