Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-09-01
2003-09-02
Dunn, Tom (Department: 1725)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S702000, C428S930000, C505S234000, C505S238000, C505S230000, C505S430000, C505S500000
Reexamination Certificate
active
06613463
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a superconducting laminated oxide substrate that can be used as the substrate of electronic devices such as superconducting devices, and a method of producing the same, and a method of producing a superconducting integrated circuit.
This application is based on Japanese Patent Applications (Japanese Patent Application No. Hei 11-252309 and Japanese Patent Application No. Hei 11-277616) filed in Japan, the contents of which are incorporated herein as a part of this specification.
2. Background Art
Use of a superconducting material generally makes it possible to decrease the high-frequency surface resistivity and operate a super conducting tunnel effect device at a high speed with lower power consumption. Thus attempts have been made to apply superconducting materials having such characteristics to electronic devices comprising high-frequency circuits. Super conducting electronic devices made of superconducting materials include superconducting integrated circuits. Superconducting integrated circuits are made by forming wiring consisting of a superconducting thin film via an insulation layer on a super conducting crystal substrate made of a superconducting oxide single crystal or a superconducting oxide polycrystal of Y—Ba—Cu—O.
With the method of the prior art, superconducting integrated circuits of the constitution described above have been made by a process in which a rod of the superconducting oxide single crystal or superconducting oxide polycrystal of Y—Ba—Cu—O is formed by a withdrawal method, and a superconducting oxide crystal substrate having a sheet shape, having a high degree of flatness, is made by slicing the rod and polishing, then forming an insulation film and a superconducting thin film on the superconducting oxide crystal substrate by a chemical vapor phase deposition process (CVD process), and forming the pattern of a superconducting circuit by photolithography process. The substrate is also heated as required, in order to improve the superconducting characteristics of the superconducting thin film that constitutes the superconducting circuit such as the critical current density.
The method of producing a superconducting integrated circuit of the prior art, however, involves heat treatment wherein the substrate is heated when forming the insulation film or the superconducting thin film for the circuit on the superconducting oxide crystal substrate, or heat treatment for heating the substrate to improve the superconducting characteristics. There has been the problem that thermal stress generated by the heat treatment, mechanical shock in a handling time, or the like, tends to cause defects such as cracks in the superconducting substrate resulting in a low production yield.
The problem described above becomes conspicuous particularly when producing superconducting integrated circuits of large sizes.
SUMMARY OF THE INVENTION
An object of the present invention is to achieve at least one of the goals of preventing cracks from occurring in the superconducting oxide crystal substrate due to the heat treatment conducted for the purpose of forming an insulation film or a conductor film on the superconducting oxide crystal substrate or a dielectric substrate that has a high degree of flatness and high degree of crystallinity and is used as the substrate of an electronic device whereon the insulation film and the conductive film to form a circuit are formed, and to provide easy connectivity between electrodes and wiring formed on substrates located at upper and lower positions.
In order to achieve the objects described above, the present invention provides a superconducting laminated oxide substrate comprising a laminate of a layer of a superconducting oxide crystal substrate made of a superconducting oxide single crystal or a superconducting oxide polycrystal, and a layer of a reinforcing crystal substrate.
The first aspect of the present invention employs a superconducting laminated oxide substrate formed by thermal compression bonding of the superconducting oxide crystal substrate consisting of a superconducting oxide single crystal or a superconducting oxide polycrystal and the reinforcing crystal substrate.
As a means of producing the superconducting laminated oxide substrate of the first aspect of the present invention, there is employed a method of producing a superconducting laminated oxide substrate, which comprises bringing a superconducting oxide crystal substrate made of a superconducting oxide single crystal or a superconducting oxide polycrystal into contact with a reinforcing crystal substrate and subjecting them to heat treatment, thereby bonding said superconducting oxide crystal substrate and said reinforcing crystal substrate on the interface thereof.
As a means of producing the superconducting laminated oxide substrate of the first aspect of the present invention, there is employed a method of producing a superconducting laminated oxide substrate, which comprises sandwiching a superconducting oxide crystal substrate made of a superconducting oxide single crystal or a superconducting oxide polycrystal by reinforcing crystal substrates on both sides thereof, subjecting to a heat treatment, thereby bonding the reinforcing crystal substrates onto both surfaces of the superconducting oxide crystal substrate, and slicing the superconducting oxide crystal substrate along a plane parallel to the surface.
In order to achieve the object described above, in the second aspect of the present invention, there may be employed a superconducting laminated oxide substrate according to claim
1
, wherein the superconducting oxide crystal substrate made of the superconducting oxide single crystal or superconducting oxide polycrystal and the reinforcing crystal substrate are bonded by thermal compression.
As the method of producing the superconducting laminated oxide substrate of the second aspect of the present invention, there is employed a method of producing a superconducting laminated oxide substrate, which comprises bringing a superconducting oxide crystal substrate made of a superconducting oxide single crystal or a superconducting oxide polycrystal into contact with a superconducting thin oxide film of a reinforcing crystal substrate having the superconducting thin oxide film formed on the surface thereof and subjecting to a heat treatment, thereby bonding said superconducting oxide crystal substrate and said superconducting thin oxide film on the interface thereof.
In order to achieve the object described above, the third aspect of the present invention employs a superconducting laminated oxide substrate made by bonding the superconducting oxide crystal substrate consisting of a superconducting oxide single crystal or a superconducting oxide polycrystal and the reinforcing crystal substrate via an intermediate layer consisting of one or more layers, while at least the outermost layer of the intermediate layer is made of a low melting point material that melts at a temperature lower than the decomposition temperature of the superconducting oxide single crystal or the superconducting oxide polycrystal that constitutes the superconducting oxide crystal substrate.
As the method of producing the superconducting laminated oxide substrate of the third aspect of the present invention, there is employed a method of producing a superconducting laminated oxide substrate, which comprises disposing an intermediate layer having, at least in the outermost layer thereof, a low melting point layer that is made of a low melting-point material which melts at a temperature lower than the decomposition temperature of superconducting oxide single crystal or superconducting oxide polycrystal that constitutes a superconducting oxide crystal substrate between the superconducting oxide crystal substrate consisting of the superconducting oxide single crystal or the superconducting oxide polycrystal and a reinforcing crystal substrate, and applying a heat treatment to fuse the low melting point layer of
Egami Masahiro
Enomoto Youichi
Iiyama Michitomo
Izumi Teruo
Koyama Satoshi
Cooke Colleen P.
Dunn Tom
Hartwell, P.C. Kolisch
International Superconductivity Technology Center
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