JPS63224117A - Manufacture of superconductor - Google Patents

Abstract

PURPOSE:To make it possible to form a ceramic superconductor substantially into a coil, a disc, a film, a wire, or a ribbon by denaturing only a portion of a ceramic material formed on the surface of a base substance into a superconducting material of an oxide, when the portion is selectively irradiated and scanned by laser beams. CONSTITUTION:A ceramic film having a thickness of 0.1-20mum, for example of 2mum, is formed on a plate shaped base substance 1 formed by using alumina, glass or YSZ as a ceramic material. The base substance is placed in an atmosphere heated up to 250 deg.C for instance and same oxygen gas is added to argon gas; after that it is scanned continuously in the oxiding ambient by excimer laser beams 3 (wavelength: 0.25mum) as shown with a broken line. Then only the portion irradiated by the laser beams is selectively oxidized and crystals are precisely arrayed to enable one to manufacture a ribbon-shaped superconducting film of 10 cm in width. Thus a domain which has a superconductive critical temperature in a ribbon shape or a wire shape can be virtually obtained by irradiation of laser beams or intense rays of light.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to thin film ceramic superconducting materials. The present invention provides a belt-like (
This is a method for producing a superconductor in which continuous patterning (substantially banded or wire-wound on a substrate) is performed by scanning while irradiating a laser beam (or linearly). The aim is to create superconducting electronic devices using this ceramic superconducting material.

"Prior Art" Conventionally, a metal material of Nb-Ge (for example, Nb1Ge) has been used as a superconducting material. Since this material is a metal, it has high ductility and malleability, making it possible to wind coils for superconducting magnets.

However, superconducting materials using these metal materials have Tc (
The superconducting critical temperature (hereinafter simply referred to as Tc) is small at 23°.
Only K or less. On the other hand, considering industrial applications, this Tc is 30'K, preferably 77°.
K or more is even more effective. especially? ?
” If a superconducting material with Tc at a temperature higher than K is developed, it will be possible to operate in a liquid nitrogen temperature atmosphere, and the industrial operation and maintenance cost will be reduced to about 1/10 or less than the current cost. is expected to be possible.

"Conventional Problems" For this reason, ceramic materials, especially oxide ceramic materials, rather than metals, are attracting attention as materials with high Tc. However, this ceramic superconducting material, which is attracting attention, has a high Tc.

It has poor bendability, ductility, and malleability, and cracks even when bent slightly. In fact, it was thought to be completely impossible to form a thin film of 0.1 to 10 μm on a substrate and make part or all of this thin film superconducting. . In particular, multilayer wiring is performed using photolithography technology similar to that used for semiconductor integrated circuits. Furthermore, it was completely impossible to create new electronic devices using this thin film superconductor.

"Means to Solve the Problem" The present invention aims to form such a thin film and use this thin film to produce an electronic device.

In the present invention, a ceramic material, particularly an oxide ceramic material, or a metal material that becomes an oxide ceramic after annealing in an oxidizing atmosphere is applied to a substrate having a desired shape in advance, such as a cylindrical or plate-shaped substrate, in the form of a thin film by sputtering or printing. For example, it is formed by screen printing or other methods.

When formed by this sputtering method, this thin film exhibits an amorphous structure or a polycrystalline structure having microcrystals having a large amount of lattice distortion and lattice defects. This structure is generally conductive or insulating without semiconducting or superconducting properties.

For this reason, the present invention includes a step of selectively irradiating and scanning a film in such a state with a laser beam to recrystallize it into a band shape having a constant width. Through this process, a laser annealing process is performed only on the area irradiated with laser light to increase the crystallization rate (increase the crystal grain size and create a microcrystalline structure exhibiting superconductivity), and only within this area, lattice strain and lattice At the same time, since it is melted and recrystallized, impurities other than the crystal structure that should originally have superconductivity are segregated to some extent on the irradiated surface, removing internal impurities and achieving high purity. It can be done.

Then, only this portion can be made of a superconducting material having a constant Tc. Thin films formed by this sputtering method etc. are prepared using ceramic superconducting materials such as (Yl) by adjusting the target.
-g Bax) CuOz, s~*, s where x = 0. O
1 to 0.1, preferably 0.05 to 0.1 of intrum ceramic material or (Lat-xBaX)gCu
Oa (BLCO).

(Lat-x Srx) g (SLCO), generally expressed as (Lat-x AX)1Cu04 However, A is B
A target material that could be A, Sr, or others was used.

The laser light source of the present invention is, for example, a YAG laser (wavelength 1.0
6μ), excimer laser (KrF, KrC1, etc.), carbon dioxide laser, or nitrogen laser. The former can be repeatedly irradiated with a circular laser beam at a frequency of 5 to 30 KHz, and only the irradiated portion is recrystallized, so that the molecular arrangement with a layered structure is further formed into a layered structure along the surface of the substrate. The feature is that this portion can be made of superconducting material by disposing it. In addition, when using the latter excimer laser, it is possible to irradiate pulses on a surface of, for example, 20 x 30 mm.The present invention uses an optical system to narrow this down to a circle (10 to 100 μm in diameter).
Or strip-shaped (width 5-100 ptm length 10-40cm)
) A laser beam can be created (1), and the substrate or the laser beam is continuously moved while irradiating the ceramic film with this laser beam. In other words, the crystal grain size of the annealed area to be scanned can be made close to (larger than) a single crystal.
Upper-conducting Material
On In5ulator).

The present invention is characterized in that the ceramic material formed on the surface of the base body is selectively irradiated and scanned with a laser beam so that only that portion is transformed into an oxide superconducting material. Then, the remaining region of this peripheral part becomes a substantially insulating region (at humidity below Tc, the resistance is theoretically sufficiently higher than that of the superconducting part, and it is possible to make it an insulating region. Although it is possible to remove the material, it is also possible to use the material to fill in the recessed portions in order to reduce the level difference in the multilayer wiring.

In the present invention, alumina, a silicon oxide substrate, and YSZ (yttoria stabilized zircon) are used as substrate materials.
, a silicon nitride substrate, aluminum nitride, zirconia, and ittria were used. However, Y with the most similar coefficient of thermal expansion
SZ, ittria, or zirconia can provide a high Tc after laser annealing.

In the present invention, an insulating substrate that is sufficiently (at least one order of magnitude more reliable) than a thermally conductive material is used as the substrate.

``Operation'' When using conventional metal superconducting materials, the first step is to make them into wire rods. A coil was then constructed by wrapping this around a predetermined base.

However, with regard to the ceramic superconductor of the present invention, a substrate in the final shape is provided, and a material that is to exhibit superconductivity after crystallization treatment is formed in a band shape on this substrate in the form of a film (which does not exhibit superconductivity as it is). By selectively performing laser annealing on this film, the degree of crystallinity is improved only in the annealed portions. By scanning this laser beam arbitrarily, it is possible to derive an arbitrary line, band, or plane only on the surface area. And only this area T
At temperatures below c, the resistance decreases, and at Tco (the temperature at which the electrical resistance becomes zero), the resistance can be at or close to zero.

The present invention will be explained below according to examples.

"Example 1" FIG. 1 shows the manufacturing process of the present invention.

In FIG. 1A, the substrate (1) is made of a ceramic material such as alumina, glass or VSZ. Metals may also be used; in these cases, the thickness is comparable to that of ceramic thin films (±5
It is preferable that the difference in thermal expansion coefficient is within 0%. If this difference is too large, stress distortion will occur after annealing, the temperature at which superconductivity is exhibited will be low, and superconductivity will no longer be observed. In the example, the film was formed on a plate-shaped substrate by sputtering to a thickness of 0.1 to 20 μm, for example, 2 μm. When this person becomes a grasshopper, the target is (Yl-X Bax)*Cu0g, s ~ s. For example, a sufficiently mixed product was used as X-0,075.

It is made into flying particles by sputtering, and a film (2
) was formed. At this time, the substrate temperature is between room temperature and 400°C, for example, 2
Some oxygen was added to the argon in an atmosphere heated to 50°C. After the shape shown in Figure 1 (B) is created in this way, the shape shown in Figure 1 (C) is created.
), excimer laser light (
While irradiating with light (wavelength: 0.25 μm) (3), continuous scanning is performed as shown by the broken line. Since this is pulsed light, one rectangular spot was made to overlap 80 to 98% of the next rectangular beam so that the pulse scanned the carpet. That is, the scanning speed of the laser beam is 2 cys/min, and the frequency is 100
KHz, beam diameter 50μta, X10cn+.

Then, only the portions irradiated with this laser light are selectively oxidized, and crystals are arranged microscopically. We were able to create a strip-shaped superconducting thin film with a width of 10 cm. In order not to make the rate of recrystallization too steep, during the process shown in Figure 1 (C),
Laser annealing or optical annealing was performed on the entire substrate in an oxygen atmosphere heated to a temperature of 200 to 800°C, for example 600°C, using a halogen lamp. Then, the temperature of the portion irradiated with laser light or equivalent intense light was 1000° C. or higher, at a temperature at which the irradiated ceramic material would not sublime. The occurrence of cranks could be prevented by rapid cooling to room temperature after irradiation with light. In this example, Tc was 43''K.

Thus, by irradiating this laser light or strong light, it was possible to create a region having Tc substantially in the form of a band or line.

"Example 2" FIG. 2 shows another embodiment of the invention.

In the drawing, the base body ('1) has a cylindrical shape. Here, similarly to Example 1, a ceramic material (2) is formed in the form of a film by sputtering.

For this production, use a sputtering device to connect this cylindrical substrate to the arrow (12).
The coating may be applied while rotating as shown in the figure.

Next, while irradiating the substrate on which these films are formed with the WAG laser (3) beam diameter (5011 m), this laser light (
Gradually move the cylinder in the direction of 11), and at the same time move the cylinder in the direction of arrow (12).
Rotate in the direction of. Then, a region (4) having one continuous band-like Tc can be formed on this cylindrical substrate. The adjacent portion (5) is left as a region without Tc. In other words, it was possible to construct a superconducting magnet coil that is essentially the same as a thermoelectric wire formed in a coil shape.

FIG. 4 shows a multi-layered superconducting wire formed by repeating these steps.

This corresponds to 0
The structure of the drawing is abbreviated.

The first ceramic material is coated (2-1) on the substrate (1), and then laser light is applied (4-1), (4
-2)... (4, -n) is irradiated. This can be accomplished by moving the laser beam to the right while rotating the substrate. Then, this laser light is irradiated while scanning continuously, and only the thermally annealed region is transformed into a superconducting material.

Next, a film coating (2-2) of a second ceramic material is formed on these. Further, laser annealing is performed in the same manner to form a region (4'-n) having a band-shaped Tc.

...(4'-2), (4"-1) is created.At this time, the laser tends to bleed downward because it is relatively difficult to control the depth, so (4"-1), (4
'-2) is the region (4-1) with Tc below it.
), (4-2) . . . and are arranged above the Tc-free regions (5-1), (5-2) . This (4-1) goes around the coil once and (4-1)
2) is electrically linked. (4-n) of these ends
In this case, it is connected to (4'-n) of the second layer at (10-1).

Furthermore, the other end (4'-1) of the second layer is connected to (4''-1) and (10-2) of the third layer, and the region having Tc of the third layer is connected to (4'-1) of the third layer. ”-1), (4”-2) ・
...(4"-n), and further connects with the fourth layer at (10-3). Thus, the multilayer structure (here, 4"
Even with a layered structure, one long wire is wound repeatedly, and the structure can be substantially the same as multilayer winding of a coil.

In the embodiment shown in FIG. 4, (5-1) and (5-2) are made to have approximately five times the width of (4-1) and (4-2),
(4”-1), <4°゛-1) (4°°”-1) is (5
-1) is formed above the lead wires to prevent short-circuiting of the lead wires between each eyebrow. By repeating this process, multilayer wiring can have one to several tens of layers. Also, in this case, they were connected in series as if they were one superconductor. However, depending on the application, they may be connected in parallel, and external extraction electrodes and leads (30) and (30') were provided.

The rest is the same as in Example 1.

"Example 3" FIG. 3 is a drawing showing another embodiment of the present invention.

In the drawing, a base (1) has a disk shape, and a laser beam (3) larger than this diameter is irradiated linearly. Thereafter, this disk (1) is repeatedly and continuously rotated. Then, optical annealing can be repeated. Then, this ceramic thin film gradually aligns its crystal alignment and can grow into crystals over a large area. Thereafter, it is recrystallized along the upper surface of the substrate to form a layered structure with molecular alignment.

Although this figure shows a single-layer disk configuration, it is possible to have a multi-layer configuration similar to the embodiment shown in FIG.

Tc of the region subjected to laser annealing in this oxidizing atmosphere
obtained 43°K.

"Effects" According to the present invention, it has become possible to construct a ceramic superconductor substantially in the shape of a coil, disk, or film in the form of a wire or band, which was previously considered impossible.

As a ceramic superconducting material that easily breaks when bent, it could be made into a thin film as a solid material for conductors or superconducting elements.

In the present invention, after forming a superconducting thin film, it is important from the viewpoint of industrial application that it is subjected to a predetermined patterning process using a known photolithography technique to form a superconducting element or superconducting wiring.

The superconducting material of the present invention may be any ceramic material.

[Brief explanation of drawings]

FIG. 1 shows the manufacturing process of the superconductor of the present invention. 2, 3 and 4 show embodiments of the superconductor of the present invention. l...Substrate 2...Ceramic material 3...Laser light 4...Striped region exhibiting superconductivity 5...Region not exhibiting superconductivity

Claims (1)

[Claims] 1. A step of forming a ceramic material in the form of a thin film on a substrate, and oxidizing the ceramic material by scanning and irradiating the material with a laser beam or a strong light equivalent to it in a band shape. 1. A method for producing a superconductor, comprising the step of recrystallizing the material and transforming it into a material capable of producing a superconducting state. 2. In claim 1, a coil is formed by forming an oxide ceramic material in the form of a thin film on an insulating substrate, and irradiating the material with a laser beam in a belt shape while rotating the cylindrical substrate. 1. A method for producing a superconductor, comprising producing a region exhibiting superconductivity in a shape. 3. A method for producing a superconductor according to claim 2, comprising a substrate having a coefficient of thermal expansion approximately within ±50% after the thermal expansion of the ceramic material.