JPH01242477A - Formation of protective film on superconductor - Google Patents

Abstract

PURPOSE:To easily form a protective film which is fine in crystal grains, has a dense surface and has an excellent effect of preventing the deterioration of a bulky or film like superconducting material by projecting laser light to the surface of said superconducting material to thinly melt the surface, then rapidly cooling the material. CONSTITUTION:The superconducting material 11 (e.g.; Y-Ba-Cu-O superconducting material) formed to a bulk state or to a film shape on a substrate is prepd. The laser light (e.g.; argon)is then projected thinly to the surface of this superconducting material 11 to melt the surface and the material is rapidly cooled, by which the protective film 12 consisting of the fine crystal grains is formed on the surface of the superconducting material 11. The formed protective film 12 is hardly soluble in water, hydrofluoric acid, nitric acid, etc., and has the stable crystal structure; therefore, the deterioration of the superconducting material 11 by the water, hydrofluoric acid, nitric acid, etc., is prevented by the protective film 12. Since the protective film 12 has the same compsn. as the compsn. of the superconducting material 11, the generation of problems such as diffusion from the subsurface, etc., is obviated.

Description

[Detailed Description of the Invention] [Summary] It relates to a method for forming a protective film on a superconductor, in particular a method in which the crystal structure of a ceramic superconducting material is changed by laser annealing and a protective film is formed on the surface thereof, and Regarding the method of patterning by etching and the method of forming a conductor pattern by making the surface of a superconducting thin film an insulator, forming a protective film on a superconductor in which a protective film is formed on the surface of a superconducting material to prevent deterioration. The purpose of this study is to provide a method for patterning superconductors that is easy to manufacture and does not cause deterioration during patterning of superconducting films. The surface of the superconducting material is irradiated with a laser beam, and the surface of the superconducting material is melted into a thin layer.
A method for forming a protective film on a superconductor, the method comprising forming a protective film with fine crystal grains on the surface by rapid cooling;
A protective film with fine crystal grains is formed by forming a superconducting film on a substrate, partially irradiating the surface of the superconducting film with laser light, melting the surface of the superconducting film thinly, and rapidly cooling it. A method for patterning a superconductor, comprising the steps of: forming a superconducting thin film on a substrate; and wet etching a superconducting film on which the protective film is not formed; A method for patterning a superconductor, comprising a step of partially irradiating the surface of a conductive thin film with a laser beam, melting and rapidly cooling the superconducting thin film to convert it into an insulating film. .

[Industrial application field]

The present invention relates to a method for forming a protective film on a superconductor, and in particular a method for changing the crystal structure of a ceramic superconducting material by laser annealing and forming a protective film on the surface thereof, and a method for patterning the protective film by wet etching. The present invention relates to a method and a method of forming a conductor pattern by making the surface of a superconducting thin film an insulator.

[Conventional technology]

The impact that ceramic-based high-temperature superconductors, which exhibit a superconducting state at liquid nitrogen temperatures, have on industry is immeasurable, and the development of these high-temperature superconductors has been progressing rapidly recently. It is expected that such ceramic-based high-temperature superconductors will be made into thin films and applied to electronics fields such as circuit wiring and electronic devices.

[Problem to be solved by the invention]

In the manufacturing process of ceramic-based high-temperature superconducting materials,
Long-time annealing is required to achieve sufficient crystal growth. For example, to form a bulk or thin film superconductor on a substrate, annealing is performed at about 900° C. for about 2 to 10 hours. The surface of the superconductor formed in this way is
The crystal grains are large, about 1 μm to several μm, and the surface is uneven, forming a porous shape with crystal portions and space portions.

Therefore, water, oxygen, carbon dioxide, etc. can easily enter,
There is a problem of deterioration in that it is easy to dissolve or change in quality.

In addition, in order to apply the ceramic-based high-temperature superconducting material to electronics fields such as circuit wiring and electronic devices, patterning of this superconducting thin film is essential, but as mentioned above, it is prone to melting and deterioration. Due to this property, it is difficult to use wet etching, which is generally used for patterning.

Therefore, the present invention provides a method for forming a protective film for a superconductor in which a protective film for preventing deterioration is formed on the surface of a superconducting material, and also provides a method for forming a protective film for a superconductor without causing any effects of deterioration during patterning of the superconducting film. An object of the present invention is to provide a method for patterning a superconductor that is easy to manufacture.

[Means to solve the problem]

The above problem was solved by irradiating the surface of a superconducting material formed in bulk or as a film on a substrate with laser light, melting the surface of this superconducting material thinly, and rapidly cooling it to form a protective film with fine crystal grains on the surface. A method for forming a protective film for a superconductor, the method comprising: forming a superconducting film on a substrate; and partially irradiating the surface of the superconducting film with a laser beam, A superconductor comprising the steps of: forming a protective film with fine crystal grains by melting and rapidly cooling the surface of the film; and wet-etching the superconducting film without forming the protective film. The patterning method further includes a step of forming a superconducting thin film on a substrate, and a step of converting the superconducting thin film into an insulating film by partially irradiating the surface of the superconducting thin film with laser light, melting and rapidly cooling the superconducting thin film. The problem is solved by a superconductor patterning method characterized by comprising the following steps.

[For production]

A feature of ceramic superconducting materials is that their crystal structure is sensitive to sintering conditions, and in order to have superconducting properties, they are slowly cooled at high temperatures in an oxygen atmosphere. For this reason, the crystal grains become large and unevenness is formed on the surface, which easily deteriorates and decomposes in water, acid, etc. Therefore, when the surface of a sintered superconducting material formed in bulk or in the form of a film on a substrate is irradiated with laser light to melt it thinly and rapidly cool it, a thin protective film is formed on the surface through recrystallization. It was confirmed that this protective film has fine crystal grains, eliminates surface irregularities, forms a dense layer, exhibits strong and low solubility in water, hydrofluoric acid, and nitric acid, and has a stable crystal structure. Therefore, by forming a protective film on the surface of a superconducting material, a superconductor that is resistant to deterioration can be obtained.

Furthermore, by partially irradiating the surface of the superconducting film with laser light, a protective film is formed as described above. This protective film is resistant to acids and has a much lower etching rate than a superconducting film.

Therefore, by wet etching, the portions of the superconducting film where the protective film is not formed are removed and patterned. This protective film also prevents deterioration.

Furthermore, it is known that the superconducting properties of ceramic superconductors are strongly dependent on the amount of oxygen vacancies in the material. For example, perovskite superconducting material RBa zC
u 30X (R=yttrium (Y), erbium (
In the case of rare earths such as Er), europium (Eu), and holmium (Ho), the superconducting phase occurs when X is 6.7
Above that, below that it becomes an insulator. At this time, the superconducting phase has an orthorhombic crystal structure, and the insulator has a tetragonal crystal structure. This amount of oxygen varies depending on the atmosphere and temperature conditions during sintering.
For example, when slowly cooled at about 400°C to 500°C, it becomes orthorhombic, and when rapidly cooled, it becomes tetragonal. By using this property, the surface of a superconducting thin film formed on a substrate is partially irradiated with laser light, and this superconducting thin film is melted and rapidly cooled, turning it into an insulating film and directly forming a superconducting thin film. Can be patterned.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to an illustrated embodiment.

FIG. 1 is a diagram showing the manufacturing process of a superconductor according to a first embodiment of the present invention.

First, as shown in FIG. 4A, a bulk material is sintered at high temperature to form a superconducting material 11 exhibiting superconducting properties. As such a superconducting material 11, for example, Y+Baz Cu3
The method for producing the 0x sintered body (orthorhombic perovskite, which becomes superconducting at liquid nitrogen temperature) is as follows.

-Y2O3+2 BaCO3+3Cu0 is mixed and calcined in air at 850°C for 10 hours.

Next, pulverization, mixing, and powder compaction are performed at 300 kgf/cnl, followed by firing in air at 950°C for 10 hours. next,
Cooling is performed at 0.5°C/min to obtain a sintered body of 'f, 3a2C+gOx.

Next, as shown in FIG. 1 [ex. A protective film 12 is formed. At this time, the laser beam irradiation conditions are, for example, a laser output of about 1.1 watts and a scanning speed of about 150 mm/sec, so that no cracks or bubbles are generated on the surface.

Then, as shown in FIG. 1(C), a laser beam is irradiated,
A protective film 12 is formed on the entire surface of the superconducting material 11.

Since the protective film 12 formed as described above is rapidly cooled, the crystal grains are very fine, the surface is dense, it is hardly soluble in water, hydrofluoric acid, nitric acid, etc., and the crystal structure is stable. Therefore, the protective film 12 prevents the internal superconducting material 11 from deteriorating due to dissolution of water, hydrofluoric acid, nitric acid, etc., or deterioration. Furthermore, since the protective film 12 has the same composition as the superconducting material 11, there is no problem such as diffusion from the underlying layer. Above protective film 1
The superconducting material 11 on which 2 is formed can be used as is, or
It can be used for pellets, etc., and can be stored for a long time even in the presence of moisture, and can withstand changes over time.

FIG. 2 is a diagram showing a method of patterning a superconductor according to a second embodiment of the present invention.

First, as shown in FIG. 2(a), a relatively thick superconducting film 22 having a thickness of about 10 μm is formed on a substrate 21.

Such a superconducting film 22 is produced by mixing the above ceramic superconducting powder in a solvent and spin-coding it onto the substrate 21.
It is formed by forming a film on top and then sintering it. Substrate 21
For example, sapphire (R surface), Mg0 (1
00 plane), 5rTiO3 (110 plane), etc. were used.

Next, as shown in FIG. 2(b), the surface of the superconducting film 22 is partially irradiated with a laser beam to melt and rapidly cool the surface of the superconducting film 22, thereby forming a protective film 23. Form. As a result, a pattern of the protective film 23 of about 100 μm is formed.

Next, as shown in FIG. 2(C), etching is performed using phosphoric acid or the like.The etching rate of the protection film 23 is low, and the portion of the superconducting film 22 without the protection film 23 is quickly removed.
patterned.

According to the above method, the protective film 23 formed by laser beam irradiation is difficult to be etched or notched by phosphoric acid or the like.
Patterning can be performed by removing the portion of the superconducting film 22 that does not have the protective film 23. Further, the remaining protective film 23 plays a role in preventing deterioration. Through such patterning, circuit wiring and the like can be formed.

FIG. 3 is a diagram showing a method for patterning a superconductor according to a third embodiment of the present invention.

First, as shown in FIG. 3(a), about 5,000 to 10,000 ceramic superconducting materials are deposited on a substrate 31 by sputtering or electron beam (EB) evaporation, and then sintered at a predetermined temperature in oxygen. Then, a superconducting thin film 32 is formed.

For example, to create the above-described Y, Ba2Cu30x sintered body for film formation by sputtering, first, the Y, Ba2Cu30x sintered body is prepared by the method shown in the first embodiment.
A 0x sintered body is obtained.

Next, this sintered body was crushed, and BaCO3 powder (ratio of 2 to Y) and CuO powder (ratio of 2 to Y) were added to it, so that the ratio of Y, Ba, and Cu was 1:4: Make it 5. This ratio is changed as appropriate depending on the sputtering apparatus. Ba
CO3 powder and CuO powder are mixed to obtain a powder having a composition of Y+Ba1Cu50X.

Then, it was compacted into a target and heated in oxygen at 500°Cl.
Calculate for 2 hours. A film was formed from this target by sputtering, and the film was deposited in an oxygen (0□) atmosphere as shown in Figure 4.
900°C, lhr ) + (400°C, 2hr
), a superconducting thin film 32 exhibiting a superconducting state at liquid nitrogen temperature was formed. For the substrate 31, sapphire, MgO, 5rTiO+, etc. were used.

Next, as shown in FIG. 3(b), the optical system is adjusted so that the argon laser is focused on the surface of the superconducting thin film 32, and the laser beam irradiation conditions are such that the laser output is 1.1 W.
When the periphery of the pattern is scanned at a scanning speed of about 150 mm/sec, the entire portion irradiated with the laser is melted and rapidly cooled in the film thickness direction, turning into an insulating film 33. This is due to the fact that, as mentioned above, the ceramic superconductor strongly depends on the amount of oxygen vacancies, and when slowly cooled, the superconductor becomes an orthorhombic crystal, and when rapidly cooled, the ceramic superconductor becomes a tetragonal insulator. In this case, the insulating area does not need to be filled in, and only needs to be surrounded by an insulator.

According to the above method, by irradiating the conductive thin film with argon laser light, melting it, cooling it, and converting it into an insulating film 33,
It becomes possible to directly pattern the superconducting thin film 32. In this embodiment, since wet etching is not used and no chemicals or solvents are used, there is no deterioration or deterioration of the superconducting thin film 32 (also, there is no contamination or damage to the superconducting thin film 32 unlike dry etching). A thin film pattern with good characteristics can be obtained.In addition, the crystal grains in the laser irradiated area are dense and the crystal structure is stable.Furthermore, with this method, the film surface after patterning remains flat without any unevenness.
This has the advantage of eliminating problems with steps and flattening, and it becomes easier to form other protective films on the surface.

The patterning method described above can be applied to the production of superconductor circuit wiring, electronic devices, etc.

In addition, in the above example, it is explained that by irradiating the superconductor with a laser, it is melted, rapidly cooled, and transformed from orthorhombic to tetragonal depending on the amount of oxygen defects, but the conditions depend on the annealing conditions and the material. The conditions vary depending on the crystal structure and are not limited to the conditions in the examples.

In addition, although yttrium (Y) has been explained above as an example, the scope of application of the present invention is not limited to that case, but scandium (Sc), lanthanum (La), neodymium (Nd), which has a +3 valence oxidation state, ), samarium (Sm
), gadolinium (Gd), dysprosium (Dy),
Holmium (Ho), Erbium (Er), Thulium (
Tm), lutetium (Lu), promethium (Pm),
Using europium (Eu) and ytterbium (Yb)
This also applies to cases where there are

[Effects of the Invention] As described above, according to the present invention, by laser annealing the surface of a superconducting material, the crystal structure is changed and a
Since the I film is formed, deterioration of the superconducting material inside can be prevented.

Further, by forming this protective film thinly on the surface partially, patterning can be performed by wet etching.

Furthermore, by laser annealing the surface of the superconducting thin film to make it an insulator, a thin film patterning with a flat surface and good characteristics is formed without contaminating or damaging the film.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the manufacturing process of a superconductor according to the first embodiment of the present invention, FIG. 2 is a diagram showing the patterning method according to the second embodiment of the present invention, and FIG. 3 is a diagram showing the patterning method according to the third embodiment of the present invention. FIG. 4 is a diagram showing the annealing conditions of the third embodiment of the present invention. In the figure, 11 is a superconducting material, 12 is a protective film, 21 is a substrate, 22 is a superconducting film, 23 is a protective film, 31 is a substrate, 32 is a superconducting thin film, and 33 is an insulating film. Patent Applicant: Fujitsu Ltd. Representative Patent Attorney Akira Kukimoto 4-va Monthsai 1 3-Download Yellow I4un ↓ Honkei-no 1
2αL, Knees 7 Octopus Figure 1

Claims (1)

[Claims] 1. Superconducting material formed in bulk or as a film on a substrate (
The surface of this superconducting material (11) is irradiated with laser light, and the surface of this superconducting material (11) is
1. A method for forming a protective film for a superconductor, characterized in that a protective film (12) with fine crystal grains is formed on the surface of a superconductor by melting the surface thinly and rapidly cooling the surface. 2. Forming a superconducting film (22) on the substrate (21), and partially irradiating the surface of the superconducting film (22) with a laser beam to thin the surface of the superconducting film (22). It is characterized by comprising a step of forming a protective film (23) with fine crystal grains by melting and rapid cooling, and a step of wet etching the superconducting film (22) on which the protective film (23) is not formed. The method according to claim 1. 3. Forming a superconducting thin film (32) on the substrate (31); partially irradiating the surface of the superconducting thin film (32) with laser light to melt and rapidly cool the superconducting thin film (32); Method according to claim 1, characterized in that it comprises the step of converting the insulating film (33) into an insulating film (33).