JPH02125863A - Formation of oxide superconductor and device therefor - Google Patents

Abstract

PURPOSE:To form an oxide superconductor thin film having good superconductivity in a short time by irradiating the surface of a substrate on which an oxide superconductor is being formed by vacuum deposition with the oxygen-based active species formed by high-temp. unbalanced or balanced plasma. CONSTITUTION:A deposition chamber 10 is evacuated in direction of the arrow 16 through a valve 18, and the substrate 15 held at a specified temp. by an IR lamp 81 is arranged in the chamber 10. Meanwhile, the metals such as Cu, Ba, and Y constituting the oxide superconductor are vaporized respectively through electron-beam vaporization sources 41-43. The vaporized metals are deposited on the surface of the substrate 15 to form the thin film of the Ba-Y-Cu alloy having a specified composition. In this vacuum deposition, oxygen is introduced into a water-cooled discharge tube 21 adjacent to the deposition chamber 10, and high-temp. unbalanced plasma or high-temp. balanced plasma 27 is generated by a high-frequency coil 22. The surface of the substrate 15 on which a film is being formed is irradiated with the oxygen-based active species 28 formed by the plasma 27 from an orifice 50 through a differential evacuation chamber 30. By this method, the oxide superconducting thin film of Ba2YCu3Ox, etc., is efficiently formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improved method and apparatus for producing an oxide superconductor thin film.

(Prior Art) In recent years, oxide superconductors have been discovered and their technological development is proceeding at a rapid pace. - It is known that the oxygen content of oxide superconductors greatly affects their superconducting properties, and it is extremely difficult to control the oxygen concentration in superconductors.

For example, Ba2YCu, O, (X may be zero)
When creating a superconductor, zeta-lium carbonate (Bac
on), yttrium oxide (Y2O2), oxidized steel (Cu
O) was mixed in a predetermined ratio and then compression molded to make l\let, and the pellet was heated at 930°C in an oxygen atmosphere furnace.
The temperature has risen to . The pellet now exhibits a tetragonal structure. However, this sample does not exhibit superconducting properties due to its low oxygen content. (Hereinafter, this type of material will be referred to as a tetragonal material).

In order to adjust the oxygen content to an appropriate value and make the best superconducting material, it is necessary to perform annealing in an oxygen atmosphere at 930°C over a day in a furnace. In this case, it becomes orthorhombic and exhibits superconducting properties at temperatures around 90°C or lower. (Hereafter, we will refer to this type of substance as an orthorhombic substance.)

However, in order to obtain good superconducting properties, as mentioned above, it is necessary to cool down the furnace in an oxygen atmosphere for one day, which does not allow mass production on an industrial basis.

B. G. Bagley et al. in their paper (Appl. Ph.
ys, Let, ↑.

5] (1987) P, 622-P, 624), by high-frequency discharge treatment in an oxygen atmosphere, a tetragonal system substance that does not exhibit superconducting properties becomes an orthorhombic system and exhibits superconducting properties. It shows that it will become.

However, in this case as well, in order to obtain superconducting properties of 90-degree
The above-mentioned treatment for 85 hours is required, and like the above-mentioned treatment, this cannot be used industrially L'.

S., Minomo et al. in their paper (, Itln-J, A.
11p1. Phb・s4ヱ(1988) P, L411-
P, LaI3), when ECR discharge treatment is performed, 80
90% superconducting material is treated at 400°C for 130 minutes.
This shows that the superconducting properties can be improved to K class, but this is because the superconducting properties have been improved by processing the sample that originally had superconducting properties, and the tetragonal crystal which does not show superconducting properties Superconducting properties are not created by changing the crystal structure of the substances in the system.

Slightly, 19863 35th Applied Physics Related Conference 29
In a-X-5, Kakaku et al. succeeded in locally changing a tetragonal material to an orthorhombic material by oxygen ion implantation and laser annealing. It was limited and could not be applied to mass production of large areas of the lateral sole.

Examples of using the vapor deposition method to produce superconductors include B,
C1h paper (Appl, Phys, Let, t, 5
1,852 (1987)).

This is done while introducing oxygen into the reaction chamber.
Three metals, barium and copper, are simultaneously deposited on the substrate surface using an electron beam evaporation source to form a thin film. Then, this thin film is annealed in an oxygen atmosphere at 650°C for 3 to 6 hours, 750°C for 1 hour, or 850°C for 1 hour, and then slowly cooled in an annealing furnace to obtain a superconducting thin film. ing. Therefore, in this case as well, it is natural that manufacturing takes a long time.

(Problem to be solved by the invention) As described above, in order to obtain an orthorhombic substance with good superconducting properties, regardless of the manufacturing method, long-term processing is required. However, all conventional methods have problems in mass production.

(Objective of the Invention) The present invention solves this problem and provides a novel production method that can produce an oxide superconductor thin film with good superconducting properties in a short time without requiring annealing such as slow cooling from high temperatures. The purpose is to provide such equipment.

(Means for Solving the Problems) The present invention provides that, during the production of an oxide superconductor on the surface of a substrate by vacuum evaporation, oxygen-based active species created by high-temperature nonequilibrium plasma or high-temperature equilibrium plasma are applied to the surface of the substrate. A manufacturing method using irradiation: This achieves the above objective.

Particularly when the oxide superconductor has a composition of B a 2 Y Cu 30 y, the method of the present invention has shown good results.

The apparatus for realizing the method of the present invention includes a substrate, a temperature adjustment mechanism for adjusting the temperature of the substrate, and an evaporation source for evaporating the element constituting the oxide superconductor or the compound containing the element. A device in which the chamber and a discharge chamber for producing a high-temperature non-equilibrium plasma or a high-temperature equilibrium plasma are communicatively coupled via a valve, or via a differential pumping chamber provided with an orifice that communicates with each of the two chambers. The equipment will be adopted.

(Operation) High-temperature non-equilibrium plasma or high-temperature equilibrium plasma generates a large amount of atomic oxygen-based active species within this oxygen plasma.

This active species has a large diffusion coefficient in solids and has the property of rapidly diffusing at low temperatures. By irradiating such oxygen-based active species onto the surface of an oxide superconductor or superconductor raw material being produced by vapor deposition, an oxide superconductor with excellent superconducting properties or an oxide superconducting raw material containing a large amount of oxygen can be produced. You can create something on the spot.

The sample does not need to be annealed and slowly cooled, or at least the time can be significantly reduced.

(Example) The present invention is disclosed in the patent application filed in 1986-06 filed by the applicant of the present application.
No. 9646, ``Surface Treatment Method and Apparatus,'' is utilized for the production of oxide superconductors, which were not generally known at the time of filing.

"LTE plasma" in the specification of the above patent application corresponds to "high-temperature nonequilibrium plasma or high-temperature equilibrium plasma" as used in the present specification.

FIG. 1 shows a schematic front sectional view of an apparatus according to an embodiment of the present invention. 10 is a deposition chamber made of stainless steel, and a valve 18 is connected to an exhaust device in the direction of arrow 16. The substrate holder 12 holding the substrate 15 is heated by an infrared lamp 81 at 450°C.
It is possible to raise the temperature above °C. The temperature of the substrate holder 12 is measured by a thermocouple 82, and P, PI, PID
The power of the lamp 81 is adjusted by ON/OFF control using a control or a relay. When necessary, a cooling mechanism such as water cooling is used in conjunction with this. 83 is a vacuum gauge.

Reference numeral 21 denotes a discharge tube, which is a double tube made of quartz glass, and is designed to be cooled by water flowing between the double tubes. 26.26' indicates the flow of cooling water.

22 is a coil made of a copper vibrator, and the inside of the pipe (not shown) is water-cooled. One end of the coil 22 is grounded, and the other end is connected to a high frequency power source 24 through a matching circuit 23. The frequency of the high frequency power supply is 13.56MH
It is z.

The differential exhaust chamber 30 made of stainless steel and the discharge tube 21 made of quartz glass are connected using a rubber O-link (not shown). A pressure gauge 17 measures the pressure within the differential exhaust chamber 30, and the pressure is adjusted to a constant level by adjusting the valve 19 and the exhaust device connected thereto.

As described in Japanese Patent Application No. 61-069646,
When power is injected into the coil 22 from the high frequency power supply 24,
Initially, a widely spread high-frequency claw discharge occurs within the discharge tube 21. If a larger power is injected, a locally pinched high-temperature non-equilibrium plasma or high-temperature equilibrium plasma 27 is generated inside the coil 22. (About this high-temperature non-equilibrium plasma or high-temperature equilibrium alasma, please refer to Hideo Mito et al.'s "Vacuum" Vol. 31, No. 4 (1988), P271-P2?8
It is also described in detail in the literature. ) This high-temperature non-equilibrium plasma or high-temperature equilibrium plasma has an extremely high emission intensity compared to high-frequency claw discharge.
Therefore, a large amount of active species is generated, or in particular, there are many atomic active species. Additionally, electrically, it has the characteristic that the discharge impedance is significantly lower.

Depending on the pressure (at lower pressures than around 10 Torr), a glow-like discharge plasma is observed around the high-temperature nonequilibrium plasma or high-temperature equilibrium plasma 27, and the differential exhaust chamber 30
Among the active species 28 within, active species created by the high-temperature non-equilibrium plasma or the high-temperature equilibrium plasma 27 include active species caused by glow discharge.

Oxygen-based active species enter the deposition chamber 10 via the differential exhaust chamber 3o.
Regarding the lifespan of the active species when transported, J. M. Cook's paper 5olid
5tate Technology / Japanese version May
(1987) P, 2B-P, 33 and this cited literature. They discussed the downstream lifetime of oxygen atoms generated by microwave discharge, and showed that if the flow velocity is set appropriately, the lifetime of oxygen atoms can be more than 90% even 50 cm behind the plasma.

As mentioned above, oxygen is supplied from a cylinder (not shown) through a pressure reducing valve,
It is introduced from the direction of arrow 25 through a flow controller and exhausted in the direction of arrow 29 through differential exhaust chamber 30 and valve 19. The pressure in the differential exhaust chamber 30 can be read using the pressure gauge 17.
The fine adjustment to keep the pressure constant is made by adjusting the conductance of the valve 19. As the exhaust pump connected to arrow 29,
Roots pump and oil rotary pump are used. Most of the active species 28 in the differential pumping chamber 30 are exhausted in the direction of arrow 29 through the valve 19, but a portion of the active species 28 is ejected into the deposition chamber 10 through the orifice 50.

FIG. 2 is a view of the inside of the apparatus shown in FIG. 1 as viewed from arrow A-A'. The electron beam evaporation sources 41, 42, 43 are arranged rotationally symmetrically as shown in FIG. Each is C
It is an evaporation source for u, Ba, and Y.

On the other hand, the structure of each electron beam evaporation source 41, 42, 43 is as shown in FIG. Electrons emitted from a filament (electron source) 63 heated by a current from a filament power source 65 are accelerated by an accelerating electrode 64 at a higher potential than the filament 63, and become an electron beam 67. This electron beam 67 is deflected by a magnetic field 69 caused by a magnet 68.
The crucible 61 is deflected by the crucible 61 and is placed on a base 62 which is water-cooled by a cooling pipe (not shown); the surface of the contained material to be evaporated is heated and evaporated by impacting the surface of the material. Copper, barium, and yttrium, which are substances to be evaporated, are put into the melt 61.

FIG. 4 is a view taken from the arrow BB' in FIG. 1. Cop-shaped film thickness monitors 71, 72, and 73 are arranged corresponding to each evaporation source. The film thickness monitor 73 measures only the amount of evaporation from the electron beam evaporation source 43.

The pressure in the deposition chamber 10 is controlled by a pressure gauge 83, or the pressure is adjusted to a constant level by adjusting the contactance of the valve 18.

Using the apparatus of this example, a thin film was first produced in a state in which power was not applied to the coil 22 from the high-frequency power source 24, that is, in a state in which high-temperature nonequilibrium plasma or high-temperature equilibrium plasma was not generated.

Oxygen is introduced into the differential exhaust chamber 30 through the discharge tube 21 in the direction of arrow 25. The conductance of the valve 19 is adjusted so that the pressure in the differential exhaust chamber 30 becomes ITorr when the oxygen flow rate is 200 seconds. Oxygen enters the deposition chamber 10 from the differential pumping chamber 30 through an orifice 50. The conductance of the valve 16 is then adjusted so that the pressure in the deposition chamber 30 is 10-' Torr. 5rTi03 was used as the material for the base 15. and the base 15
The temperature of the electron beam evaporation source 41. is set to 600°C.
From 42.43, yttrium, barium, and copper were evaporated to form a thin film on the surface of the substrate 15.

The composition ratio of yttrium, barium, and copper in the thin film is 1:2.
The deposition rate of yttrium, barium, and copper was further adjusted so that the thin film formation rate became 600 A/min ↓ Then, when the thickness of the thin film reached about 10 μm, the deposition was stopped and the substrate 15 was deposited. It was taken out from chamber 10 and left in the atmosphere. Although the thin film in this case had a composition ratio of yttrium, barium, and copper of 1:2:3, it did not exhibit superconducting properties because of the lack of oxygen.

Next, power from the high-frequency power source 24 was applied to the coil 22 to generate high-temperature non-equilibrium plasma or high-temperature equilibrium plasma to create oxygen-based active species 28, and a thin film was produced under the same conditions as described above. , the thin film showed good superconducting properties of 90°.

Next, a superconductor using not only Ba2YCu3OX but also other Y and Ln-based elements as raw materials, ie, MBa2Cu30. .

Here, M=Y, Ln (=La,, Ce,
Pr.

Nd, Pm, Sm.

Eu, Gd, Tb.

Dy+ Hot Tm.

Y'b, Lu), other compounds with the same elemental composition and other stoichiometry, or Bl-B j 2Ca2S r 2Cu 3OXT1
System-T (12B a2Ca2Cu 3OX, other compounds with the same elemental composition and other stoichiometry, and other compounds with various elemental compositions and other stoichiometry were also tried, but none of them The method of the present invention was also effective.

The high-temperature non-equilibrium plasma or high-temperature equilibrium plasma generator used in the method of the present invention is not limited to the structure shown in FIG. Devices with various structures described in the above-mentioned Japanese Patent Application No. 61-0696413, the literature written by the inventor of the present application, "Vacuum" Vol. 31, No. 4 (+988) P,
271-P, 27B, and the devices cited therein, the present invention can achieve similar effects.

In this embodiment, elements such as copper, barium, and yttrium are used as substances to be evaporated in the crucible 61, but compounds containing such elements may be used.

For example, oxides such as cupric oxide containing copper, barium carbonate containing barium, and yttrium oxide containing yttrium may be used.

FIG. 5 shows another embodiment, in which an oxygen-based active species transport pipe 31 and a valve 32 are used instead of the differential exhaust chamber 30 in FIG.
is provided. This configuration has the advantage of omitting the differential pumping system.

In the above description, oxygen was used as the oxidizing gas, but it has been found that the same effect can be obtained by using gases such as ozone and nitrous oxide.

Furthermore, it has been found that the deposition conditions are not limited to the above-mentioned pressure, oxygen flow rate, etc., and can be selected from a fairly wide range. However, when there is a shortage of oxygen-based active species, it will not be possible to create an oxide superconductor (one that exhibits four superconducting properties), and the superconductor raw material (although it has the potential to be a superconductor in terms of composition) However, such films can be fabricated in a relatively short period of time by performing a post-process of irradiating them with the oxygen-based active species described above. It is possible to impart superconducting properties to this material.

(Effects of the Invention) As described above, according to the method and apparatus of the present invention, by utilizing oxygen active species created by high-temperature non-equilibrium plasma or high-temperature equilibrium plasma, vapor deposition can be performed in an extremely short time. In this way, an oxide superconductor or its superconductor raw material can be produced.

[Brief explanation of the drawing]

FIG. 1 is a schematic front sectional view of an apparatus according to the invention for carrying out the method according to the invention. FIG. 2 is an A-A' arrow view of the inside of the deposition chamber. FIG. 4 is the same <B-B' arrow view. FIG. 3 is a schematic front sectional view of the evaporation source. 10...Deposition chamber, 12...Substrate holder 15...
- Substrate, 21... Discharge tube, 27... High temperature nonequilibrium plasma or high temperature equilibrium plasma, 28... Active species, 30
...Differential exhaust chamber. Patent applicant: Nichiden Anelhachi Co., Ltd. Agent
Patent attorney Kenji Murakami 3゜Display of the case Patent application No. 27821 filed in 1986 Name of the invention Relationship to the case concerning the person who amends the method for producing oxide superconductors and the device Patent applicant address 581 Yotsuya, Fuchu-shi, Tokyo 5. Amendment Order 1 Co. 1 March 1999 7131 (1 for shipping) [5, Column 76 for a brief explanation of the drawings of the specification subject to amendment Supplement 1F, Contents of the specification, page 18, line 1 Insert the following sentence between the 2nd line and the month. "Figure 5 is a diagram similar to Figure 1 of another embodiment."

Claims (4)

[Claims] (1) Oxide superconductor characterized in that the surface of the substrate is irradiated with oxygen-based active species created by high-temperature non-equilibrium plasma or high-temperature equilibrium plasma while producing the oxide superconductor on the substrate surface by vacuum evaporation method. How to create the body. (2) The oxide superconductor is Ba_2YCu_3O_X
A method for producing an oxide superconductor according to claim 1, characterized in that the oxide superconductor has a composition of: (3) A substrate on whose surface the oxide superconductor is to be deposited, a temperature adjustment mechanism for adjusting the temperature of the substrate, an element constituting the oxide superconductor, or a compound or mixture containing the element. An apparatus for producing an oxide superconductor, characterized in that a deposition chamber containing an evaporation source for evaporation and a discharge chamber for producing a high-temperature non-equilibrium plasma or a high-temperature equilibrium plasma are connected so as to be able to communicate through a valve. (4) A substrate on whose surface an oxide superconductor is to be deposited, a temperature adjustment mechanism for adjusting the temperature of the substrate, and an element constituting the oxide superconductor or a compound containing the element evaporated. A deposition chamber containing a built-in evaporation source and a discharge chamber for producing high-temperature non-equilibrium plasma or high-temperature equilibrium plasma are coupled via a differential pumping chamber equipped with an orifice communicating with each of the two chambers. Oxide superconductor production equipment.