JPH0197320A - Formation of superconductive wiring pattern - Google Patents

Abstract

PURPOSE:To make it possible to use, mechanically and stably, a superconducting material having high phase transition temperature for a wiring material and form a fine wiring pattern by forming grooves based on a pattern using a photolithography. CONSTITUTION:Powder 2 of superconducting material having preferable supercon ductivity is formed in paste and a pattern is formed on a substrate using the paste, thereafter being burnt, to thereby obtain a superconductive wiring. The pattern is formed by the grooves on the surface of a substrate using a photoli thography method. A compound oxide having a composition which is represented in a general formula alphaw, betax, gammay, deltaz is used as the superconducting material, wherein an element alpha is one kind of IIa group in the periodic table, an element betais one kind of IIIa group in the periodic table, an element gamma is one kind of Ib, IIb, IIIb, VIIIa groups in the periodic table, an element delta is O and w, x, y, z are in the relationship of 1<=w<=5.1<=x<=5.1<=y<=15.1<=z<=20.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for forming superconducting wiring patterns. More specifically, the present invention relates to a method for producing a wiring made of a novel superconducting material that has a high superconducting critical temperature and a phase transition termination temperature that has a small difference from this critical temperature.

In the following description, the superconducting critical temperature is defined as the end temperature of the phase transition at which the electrical resistance of the TC1 superconductor becomes completely zero.
ci, the difference between Tc and Tci is marked as ΔT.

Conventional technology Under superconducting phenomena, materials exhibit complete diamagnetic properties, and no potential difference appears even though a finite steady-state current flows inside them. Therefore, various applications have been proposed for superconductors as transmission media with no power loss.

In other words, MHD power generation, power transmission, power storage, etc. in the power field, power fields such as magnetic levitation trains and electromagnetic propulsion ships, and ultra-high energy fields such as magnetic fields, microwaves, and radiation in the medical and measurement fields. As a sensitive sensor, there are many applications such as NMR 1π meson therapy, high energy physical experiment equipment, etc.

Furthermore, in the field of electronic devices such as Josephson devices, this technology is expected to not only reduce power consumption but also realize extremely high-speed operation.

By the way, superconducting phenomena have conventionally been observed only at extremely low temperatures. Even compared to Nb3Ge, which is said to have the highest superconducting critical temperature Tc among conventional superconducting materials, it was only 23.2.

Therefore, conventionally, in order to realize the superconducting phenomenon, superconducting materials were cooled to below Tc using liquid helium with a boiling point of 4.2. However, the use of liquid helium imposes an extremely large technical burden and cost burden due to cooling equipment including liquefaction equipment, which has hindered the practical application of superconducting technology.

On the other hand, in recent years, it has been reported that fired bodies containing oxides of LA group elements or IIIa group elements can become superconductors with high Tc, and the practical application of superconductors using non-low temperature superconductors has suddenly accelerated. has been done.

In the examples that have already been reported, it is thought that they have a crystal structure similar to that of perovskite oxides such as an orthorhombic structure [La, Ba) 2CUO4 or [1
There are complex oxides such as , a, , Sr]2cuoa. In these substances, a Tc much higher than the conventional Tc of 30 to 50 has been observed, and a Tc of 80 or higher has also been reported.

In this way, when the Tc of the superconducting material is improved, liquid nitrogen, which is easy to use and inexpensive, can be used as a cooling medium, and the superconducting phenomenon can be used industrially.

Problems to be Solved by the Invention However, the above-mentioned perovskite type or pseudo-perovskite type oxide is obtained as a so-called fired product, which is inconvenient to handle. This is because fired bodies are generally brittle and easily break even under a slight mechanical load. In particular, since superconducting materials are often used as power transmission media, they must be used in the form of thin lines, and as mentioned above, superconducting materials that are vulnerable to mechanical loads cannot be used practically. . Therefore, although superconducting materials have the extremely advantageous feature of zero electrical resistance, they have not been able to be used practically as power or signal transmission media.

Furthermore, in the field of electronic devices, although it is possible to form devices such as Josephson devices, it is difficult to form bonding wires that connect the device and other circuits using superconducting materials. Therefore, the excellent characteristics of superconducting material elements could not be effectively utilized.

SUMMARY OF THE INVENTION Therefore, the present invention aims to solve the above problems of the prior art and to enable mechanically stable use of a superconducting material having high Tc and Tci as a wiring material. Another objective is to provide a method that enables the formation of fine wiring patterns using superconducting materials.

In order to solve the problem, according to the present invention, grooves are formed according to a predetermined pattern on the surface of a flat substrate by photolithography, and at least one element α selected from group 11a of the periodic table is formed.
or a compound containing the element α, at least one element β selected from group IV a of the periodic table, or a compound containing the element β, and a compound containing the element β, Ib, nb, llIb, IVa, IVa of the periodic table;
At least one element T selected from group a or a compound containing the element T is used as a raw material powder, and the raw material powder is mixed with a vehicle to obtain a paste, and the paste is applied to the groove on the substrate. After filling, the vehicle is volatilized and removed from the paste, and the substrate coated with the paste is further heated and fired to obtain the general formula: αWβMT
y δ2 (However, element α is an element selected from group 1a of the periodic table, element β is an element selected from group IIIa of the periodic table, and element T is an element selected from group 1b of the periodic table. ,nb,m
One type of element selected from groups b and ■a, element δ is 0 (oxygen), and WSX% VN z is 1≦, respectively.
A complex oxide wiring pattern having a composition expressed by W≦5.1≦X≦5.1≦y≦15.1≦2≦20 (a number satisfying W≦5.1≦X≦5.1≦y≦15.1≦2≦20) is formed on the substrate. A method of forming a superconducting wiring pattern is provided.

SeptemberThe method for forming a superconducting wiring pattern according to the present invention involves forming a raw material powder of a superconducting material having excellent superconducting properties into a paste form, forming a pattern on a substrate using this paste, and then baking it to form a superconducting wiring pattern. Its main feature is to take Further, a further main feature of the present invention is that the above-described pattern formation is performed by grooves formed on the surface of the substrate by photolithography.

That is, since the superconducting wiring produced in this manner is formed in close contact with the substrate, it will not be damaged even during general handling. In addition to general wiring, it can also be applied to the production of small parts other than wiring, such as small coils and yokes.

Furthermore, by using the IJ lithography method, which is a unique method of forming grooves according to a fine pattern on a substrate and filling the grooves with paste, extremely fine wiring patterns can be drawn.

The superconducting material forming such superconducting wiring has the following general formula: α, β, γ, δ (However, element α is an element selected from group A of the periodic table, Element β is 1 selected from group a of the periodic table.
Element T is a species element, and element T is a member of the periodic table Ib, nb, mb,
■It is one type of element selected from group a, and element δ is 0 (
oxygen), and wSxSy and z are each 1≦W≦5.
1≦X≦5.1≦y≦y≦15.1≦2≦20) A composite oxide having a composition represented by the following is preferable. This material has effective superconducting properties in the temperature range above liquid nitrogen temperature.

As a raw material for forming such a composite oxide wiring, a powdered compound containing the above-mentioned elements α, β, and γ is used. Specifically, powders of oxides, carbonates, sulfates, or nitrates of the above elements are easily available and inexpensive.

Further, according to a preferred embodiment of the present invention, as a raw material for forming the superconducting wiring, a compound oxide of each of the above elements is fired to form a composite oxide in advance. In this case, since the complex oxide can be formed in advance under effective control, the superconducting properties after it is formed as a wiring are stabilized.

That is, first, the particle size of the raw material powder to be subjected to preliminary firing is set to 15 μm or less, particularly preferably 5 μm or less. This is because if the average particle size exceeds 5 μm, the crystal grain size will not be sufficiently refined even after the pulverization step after firing. Therefore, in order to reduce the crystal grain size in the completed wiring, it is preferable that the particle size of the raw material powder is within the above range.

In addition, the crushing process after preliminary firing has a direct effect on the crystal grain size after main firing, and if it exceeds 10 μm, the grain size of the fired body after main firing will increase and the grain boundary area will increase. Decrease. As mentioned above, grain boundary reduction is unfavorable for achieving high Tc.

In addition, the homogenization of the raw material powder or the fired body is further promoted by repeating the pre-firing → pulverizing process multiple times. In addition, the particle size of the fired powder after the final pulverization process has a close relationship with the characteristics of the product, and is
It is preferable to set it to below micrometer.

In addition, the main firing temperature is an extremely important control factor, and must be controlled so that the firing proceeds with an in-phase reaction and that the crystal growth of the fired perovskite-type or pseudo-perovskite-type oxide does not become excessive. be. On the other hand, it goes without saying that an effective sintering reaction must be promoted, and as a result of integrating these points, the main firing temperature should be set at the upper limit of the melting point of the raw material with the lowest melting point among the raw material powders, and this It is preferable that the temperature difference between the melting point and the melting point is within 100°C. In particular, the reason why the upper limit is set as the melting point is that when the raw material powder is melted, it causes a liquid phase reaction, and the characteristics of the superconducting material that has undergone such a process are significantly deteriorated.

Furthermore, for the same reason as controlling the main firing described above, if the pre-calcination temperature does not reach the above range, the solid solution reaction will not proceed sufficiently and an effective perovskite or pseudo-perovskite oxide will not be obtained. do not have.

On the other hand, if the preliminary firing temperature exceeds 950°C, as in the case of main firing, a solid solution phase will occur in the fired body or crystal grains will become coarser, making it difficult to refine them by pulverization in subsequent steps. .

Furthermore, according to the findings of the present inventors, a superconductor made of a perovskite-type or pseudo-perovskite-type oxide exhibits excellent characteristics, particularly near the surface of a fired body. This is thought to be due to the fact that near the surface of the material, the reaction with the atmosphere during firing or heat treatment progresses favorably to achieve superconducting properties, and the phase near the surface is subjected to strain effects, resulting in the appearance of excellent superconducting properties. Therefore, in the method of the present invention, it is necessary to carefully control the viscosity of the paste forming the wiring and the thickness of the coating film on the substrate.

That is, if the thickness of the applied paste is less than 10 μm, it will be difficult to form a continuous film with a uniform thickness. Also,
If the thickness exceeds 50 μm, the pattern is likely to be deformed due to so-called sag, and the characteristics of the formed wiring tend to differ between the vicinity of the substrate and the surface of the wiring.

In addition, superconducting materials made of composite oxide sintered bodies are particularly susceptible to the formation of substances with high superconducting critical temperatures at grain boundaries, that is, at interfaces between crystal grains. A unique manufacturing method results in a superconducting material with finely structured crystals and an extremely high critical temperature.

As the vehicle, ethyl cellulose resin or acrylic resin using terpionel or butyl carbitol acetate as a solvent can be used.

Further, as the substrate material, in addition to general materials such as alumina, beryllia, and aluminum nitride, particularly advantageous materials include 5rTiO5 and sapphire. These materials have crystal structures similar to those of superconducting composite oxides, and have the effect of improving the characteristics of superconducting interconnects formed directly above them.

Furthermore, according to a preferred embodiment of the present invention, the paste becomes a substantially uniform pseudo-perovskite type oxide by firing treatment. This treatment significantly increases the superconducting critical temperature at which the electrical resistance becomes completely zero. This heat treatment is desirably carried out at a temperature within 100°C, with the upper limit being the melting point of the material powder with the lowest melting point among the raw material powders forming the paste, and more preferably carried out in an oxygen-containing atmosphere. preferable. In other words, by firing under an appropriate oxygen partial pressure, oxygen defects are formed in the fired body, and carriers generated by these defects increase the probability of forming Cooper pairs, and the superconducting critical temperature at which the resistance becomes completely zero increases significantly. It is estimated that

If the heating temperature does not reach the above range, the fired product will not become the desired perovskite-type or pseudo-perovskite-type oxide, and the desired superconducting critical temperature will not be obtained, or a long heat treatment will be required. becomes. On the other hand, at a treatment temperature exceeding the above range, the perovskite crystal structure having a superconducting effect disappears, and the critical temperature drops significantly.

Furthermore, by heat treatment after firing, ΔT is further improved by 3 to 5°C. Note that the heat treatment is preferably performed under a reduced oxygen pressure of 10' torr or less. The reason for this is that if the oxygen partial pressure is higher than this, it will take a long time to form oxygen vacancies, so it is not suitable for industrial use, and if the temperature is below 500°C or above 800°C, the formation of oxygen vacancies will be too small or too large, and it will not be sufficient. This is because it is difficult to obtain a high Tci.

Furthermore, according to a preferred embodiment of the present invention, after the above-mentioned firing or after the firing, the heating is performed again to a temperature in the range of 500 to 800°C.
The superconducting critical temperature can be further improved by slow cooling at a cooling rate of 0° C./min or less. Furthermore, it has been found that by following these preferred embodiments of the present invention, the composition of the superconducting material is made uniform and stable, and as will be specifically described later, there is little deterioration of the characteristics over time.

The present invention will be specifically explained below with reference to Examples, but the technical scope of the present invention is not limited by the following disclosure.

EXAMPLE As shown in FIG. 1(a), a resist 2 was patterned on an Al2O3 substrate 1 having a purity of 96%, and after etching with hydrofluoric acid, the remaining resist was removed.

When the substrate 1 in this state was observed using a microscope, it was found that a groove 3 corresponding to the shape of the circuit was formed as shown in FIG. 1(b).

On the other hand, the paste was prepared as follows.

BaCO3 with a purity of 3N or more and an average particle size of 3μ or less, ¥2 (
13. The composition of each CuO powder after firing is BaMY.
When yCuz O7-δ, X=2, y=1z=
3. A mixed powder was prepared in which the powder was mixed so as to have a ratio of δ″−,0,1.

This powder was fired in the air at 900° C. for 12 hours, and the powder solidified into a cake was ground for 8 hours in an alumina ball mill to obtain a powder with an average particle size of 4 μm. This operation was repeated three times, and especially in the last step, the powder sintered body was pulverized to a size of 2 to 3 μm.

■ Mix the powder sintered body with polyvinyl butyral and debutyl phthalate, and further add 1:1 of isopropyl alcohol.
After mixing at a ratio of 2 parts of methyl ethyl ketone, the mixture was mixed in a ball mill for 12 hours, and then degassed and the viscosity was adjusted to 900
A slurry of cps (at 20°C) was prepared.

(2) The powder calcined body was mixed with terpineol and butyl carbitol, and then mixed with a three-way roll.

An acrylic binder and a silicone additive for imparting thixotropic properties were added to the powder fired body of (2) and mixed in a ball mill.

After applying these pastes ■, ■, and ■ onto the substrate 1 in which the grooves 3 described above have been formed, as shown in FIG. 2(a), the grooves are formed with a squeegee as shown in FIG. 2(b). The overflowing paste was scraped off and the paste was sufficiently distributed inside the groove.

These substrates were held at 900°C in a gas flow of 12
It was baked for a time to splatter the paste vehicle and bake. Thus, wiring of the composite oxide fired body is formed in the groove 3 of the substrate 1.

In addition, the critical temperature Tc and Tci of the wiring obtained in this way
The measurement was carried out using a direct current four-point probe method in a Tarabiostat with electrodes made of Ag conductive paste attached to both ends of the sample according to a standard method. The temperature has been calibrated ^u
This was carried out using a (Fe)-Ag thermocouple. Changes in resistance were measured while gradually increasing the temperature, and the measured Tc and Tci are shown in Table 1.

Furthermore, elements of group I [a and] group IIa of the periodic table were wired with the composition shown in Table 1 under the same conditions as above, and the Tc and Tci of each sample were measured using the method described above. went. Furthermore, several types of substrate materials were used as shown in Table 1.

Note that beryllia, sapphire, and 5rT1o3 were used as the substrate.

Table 1 (1) Table 1 (2) Table 1 (3) As described in detail, according to the present invention, a ceramic superconductor having the ideal property of having no electrical resistance or impedance is produced. A wiring pattern is formed using the material.

On the other hand, in recent years, progress has been made in increasing the speed of devices such as Josephson elements, but the performance of these devices naturally depends on being mounted on circuit boards and packages. In other words, no matter how much the performance of a device improves, its performance cannot be fully demonstrated unless wiring and the like as peripheral components are completed to match the improvement.

It is effective to mount devices using these superconductors on this circuit board and use them as patterns to bring out the functions.

The wiring fabricated according to the present invention exhibits extremely good superconducting properties, and these excellent properties are stable over a long period of time.

This is because, according to the characteristic manufacturing method of the present invention, the crystal optical surface length is increased by making the crystal grains finer, and the uniformity of the oxygen defect concentration is achieved, resulting in a high Tci and a small ΔT. .

Superconductors formed as wiring on a substrate are mechanically stable and easy to handle because they are supported by the substrate. It is also economical because there is no need to use more superconducting material than necessary to provide strength.

Further, by forming grooves on the substrate by photolithography and filling the grooves with paste, it is possible to form extremely fine patterns compared to screen printing methods and the like.

As described above, according to the present invention, a superconducting material having a high and stable Tc can be obtained in an easy-to-use form, so that an economical superconducting wiring using liquid nitrogen as a cooling medium can be obtained, and superconducting technology can be put to practical use. becomes possible.

[Brief explanation of the drawing]

FIGS. 1(a) and 2) and FIGS. 2(a) and 2(b) are diagrams illustrating step-by-step the method for forming a superconducting wiring pattern according to the present invention, respectively. [Main reference numbers] 1...Substrate, 2...Resist, 3...Groove, ■(■,■)...Paste patent applicant Sumitomo Electric Industries, Ltd.

Claims (34)

[Claims] (1) Grooves are formed according to a predetermined pattern on the surface of a flat substrate by photolithography, and at least one element α selected from group IIa of the periodic table is formed.
or a compound containing the element α, at least one element β selected from group IIIa of the periodic table, or a compound containing the element β, and a compound containing the element β, I b, IIb, IIIb, IVa, VII of the periodic table.
At least one element γ selected from Group Ia or a compound containing the element γ is used as a raw material powder, and the raw material powder is mixed with a vehicle to obtain a paste, and the paste is applied to the grooves on the substrate. After filling, the vehicle is volatilized and removed from the paste, and the substrate coated with the paste is heated to perform main firing. Element β is a type of element selected from group IIIa of the periodic table, and element γ is a type of element selected from group IIIa of the periodic table.
One type of element selected from groups Ib and VIIIa, element δ is O (oxygen), and w, x, y, and z are each 1≦
A complex oxide wiring pattern having a composition expressed by the following formulas (w≦5, 1≦x≦5, 1≦y≦15, 1≦z≦20) is formed on the substrate. A method for forming superconducting wiring patterns. (2) The superconducting wiring pattern according to claim 1, wherein the raw material powder is a powder of oxide, carbonate, sulfate, or nitrate of each of the elements α, β, and γ. How to form. (3) The raw material powder is obtained by pre-calcining a powder mixture of powders of oxides, carbonates, sulfates or nitrates of elements α, β and γ, and pulverizing the resulting fired body. The method for forming a superconducting wiring pattern according to claim 1, wherein the superconducting wiring pattern is a fired powder. (4) The method for forming a superconducting wiring pattern according to claim 3, wherein the preliminary firing is performed at a temperature in the range of 700 to 950°C. (5) Formation of a superconducting wiring pattern according to any one of claims 3 to 4, characterized in that a series of steps including preliminary firing and pulverization of raw material powder is repeated at least three times. Method. (6) Formation of a superconducting wiring pattern according to any one of claims 3 to 5, characterized in that the fired body after the final preliminary firing is pulverized to an average particle size of 8 μm or less. Method. (7) The method for forming a superconducting wiring pattern according to any one of claims 3 to 6, wherein the pulverization is performed using a ball mill. (8) Claim 7, characterized in that pulverization is carried out for at least 5 hours using Al_2O_3 balls.
The method for forming a superconducting wiring pattern as described in . (9) The method for forming a superconducting wiring pattern according to any one of claims 3 to 6, wherein the pulverization is performed using a jet mill. (10) Using air, Ar or N_2 as a medium, Al_
The method for forming a superconducting wiring pattern having a high critical temperature according to claim 9, characterized in that a jet stream is made to collide with a target of 2O_3. (11) Formation of a superconducting wiring pattern according to any one of claims 1 to 10, wherein each of the raw material powders has a particle size of 15 μm or less, preferably 5 μm or less. Method. (12) The method for forming a superconducting wiring pattern according to any one of claims 1 to 11, wherein the vehicle is made of a resin and a solvent. (13) The method for forming a superconducting wiring pattern according to claim 12, wherein the resin is an ethyl cellulose resin or an acrylic resin. (14) The method for forming a superconducting wiring pattern according to claim 12 or 13, wherein the solvent is terpionel or butyl carbitol acetate. (15) Claims 1 to 14, characterized in that the viscosity of the paste is 100 to 1000 poise.
The method for forming a superconducting wiring pattern according to any one of the above items. (16) The method for forming a superconducting wiring pattern according to any one of claims 1 to 15, wherein the filling of the paste is performed using a squeegee. (17) The method for forming a superconducting wiring pattern according to any one of claims 1 to 16, wherein the substrate is made of alumina. (18) The method for forming a superconducting wiring pattern according to any one of claims 1 to 16, wherein the substrate is beryllia. (19) The method for forming a superconducting wiring pattern according to any one of claims 1 to 16, wherein the substrate is made of aluminum nitride. (20) Any one of claims 1 to 16, characterized in that the substrate is SrTiO_3.
The method for forming a superconducting wiring pattern as described in . (21) The method for forming a superconducting wiring pattern according to any one of claims 1 to 16, wherein the substrate is sapphire. (22) The method for forming a superconducting wiring pattern according to any one of claims 1 to 21, wherein the depth of the groove is in a range of 10 to 50 μm. (23) Dry the applied paste for 100 to 200 minutes.
23. The method for forming a superconducting wiring pattern according to any one of claims 1 to 22, characterized in that the method is carried out at a temperature in the range of .degree. (24) A claim characterized in that the main firing is carried out at a temperature with the upper limit being the melting point of the material with the lowest melting point among the raw material powders forming the paste, and the difference from the melting point being within 100°C. The method for forming a superconducting wiring pattern according to any one of Items 1 to 23. (25) Perform main firing at O_2 partial pressure of 0.1 atm to 0.5
25. The method for forming a superconducting wiring pattern according to any one of claims 1 to 24, characterized in that the method is carried out in an oxygen-containing atmosphere at atmospheric pressure. (26) The method for forming a superconducting wiring pattern according to claim 25, wherein the main firing is performed in the atmosphere. (27) The method for forming a superconducting wiring pattern according to claim 26, wherein the main firing is performed in an oxygen atmosphere of 5 atm to 10 atm. (28) The method for forming a superconducting wiring pattern according to any one of claims 1 to 27, characterized in that the fired body after main firing is heat-treated in a range of 400 to 700°C. (29) O_2 partial pressure during heat treatment is 10^-^1Torr
The method for forming a superconducting wiring pattern according to claim 28, characterized in that: (30) Immediately after the above firing or after firing 500 to 8
The superconducting wiring pattern according to any one of claims 1 to 29, characterized in that the superconducting wiring pattern is reheated to a temperature in the range of 00°C and slowly cooled at a cooling rate of 20°C/min or less. How to form. (31) The crystal grain size of the composite oxide forming the wiring is 1
Claim 1 characterized in that it is 5 μm or less
31. The method for forming a superconducting wiring pattern according to any one of Items 30 to 30. (32) The element α is Ba, the element β is Y, and the element γ is Cu according to any one of claims 1 to 31. A method for manufacturing a superconducting member. (33) The element α is Ba, the element β is Dy, and the element γ is Cu according to any one of claims 1 to 31. A method for manufacturing a superconducting member. (34) The element α is Sr, the element β is La, and the element γ is Cu according to any one of claims 1 to 31. A method for manufacturing a superconducting member.