Process of forming superconductive wiring strip

Details Process of forming superconductive wiring strip Process of forming superconductive wiring strip

1989-08-24

1991-12-24

Bowers, Jr., Charles L.

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Making electrical device

505 1, C04B 3556, C04B 3580, G03C 500

Patent

active

050752006

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a process of forming a superconductive wiring strip and, more particularly, to a superconductive wiring strip used for fabrication of, for example, a thick film integrated circuit or a thin film integrated circuit.


BACKGROUND ART

Conventionally, the structure disclosed in "Techniques of Forming Superconductive Wiring Strip on Alumina Substrate", Electronic Parts and Materials, 1987 November, pages 89 through 92, published by Association of Industrial Investigation, is known as a typical example of the structure of the superconductive wiring strip of such an integration usage.
The superconductive wiring strip is formed on a substrate by using thick film printing techniques. In detail, a bulk solid of a superconductive ceramic material is pulverized into a powder of the superconductive ceramic material, a paste made from the powder is patterned on a high purity alumina substrate (which is known as "Fine Grained Alumina substrate" and abbreviated to "FGA") by using a screen printing technique, and, then, the patterned paste is sintered. In this way, the superconductive wiring strip is formed by using the screen printing technique.
However, since the wiring pattern is formed on the substrate by using the screen printing technique in the prior art process of forming the superconductive wiring strip, a problem is encountered in that miniature pattern geometries are hardly developed. For example, the screen printing technique is merely capable of producing conductive patters with a feature size as well as a tolerance fallen within a range between 50 microns and 100 microns.
It is therefore an object of the present invention to provide a process of forming a miniature wiring pattern of a superconductive material.


DISCLOSURE OF INVENTION

In accordance with the present invention, a process of forming a superconductive wiring strip comprises the steps of preparing an insulating layer and a raw material containing at least one element selected from the group consisting of scandium, yttrium and lanthanides, at least one alkaline earth metal and copper, forming a mask layer used for a formation of a wiring pattern on the insulating layer by using lithographic techniques, covering the mask layer and an exposed portion of the insulating layer with the raw material, thereby forming a raw material layer, leaving a part of the raw material layer and removing the other part of the raw material layer on the insulating layer by striping off the mask layer, and oxidizing the part of the raw material layer for producing the superconductive wiring strip.
The raw material may contain a plurality of elements selected from the group consisting of scandium, yttrium and lanthanides, a plurality of alkaline earth metals and copper. In the step of forming the mask layer, a photoresist is, by way of example, applied on the insulating layer, and a photo-mask image is transferred on the photoresist during an exposure, then being developed by a partial etching of the photoresist. For an improvement of the resolution in the formation of the mask layer, a radiation selected from the spectrum between a short-wavelength visible radiation and a near-ultraviolet radiation as well as any one of a deep ultraviolet radiation, an electron beam radiation, an x-ray radiation and an ion beam radiation may be available.
The raw material layer may be deposited by using any one of a vacuum evaporation technique, a sputtering technique, an ion plating technique and so on.
As described hereinbefore, the lithographic techniques are employed in the present invention for the formation of the wiring pattern, and, for this reason, a miniature wiring strip is easily produced. The superconductive ceramic wiring strip by way of example is about 0.5 to 1 micron in width. If a superconductive material of the yttrium-barium-copper-oxygen system is used for the superconductive wiring strip, the current density is increased.


BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 to 6 show the steps of a first example of a process of form

REFERENCES:
patent: 4879270 (1989-11-01), Maxfield et al.
patent: 4933318 (1990-06-01), Heijman

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