JPH0778000B2 - Method for manufacturing oxide superconducting thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an oxide superconducting thin film.

<Problems to be Solved by Conventional Techniques and Inventions> Conventionally, metal-based, ceramic-based, organic-based, etc.
Various superconductors are known, but in recent years, high critical temperature
Oxide superconductors with Tc are in the spotlight. Also,
Various techniques for forming an oxide superconducting thin film have been studied in order to make full use of the characteristics of the oxide superconductor, and as one example, a vacuum vapor deposition method in which an oxide superconductor is heated and evaporated under reduced pressure is known. On the other hand, in oxide superconductors, it is also known that the oxygen content has important significance in terms of characteristics.

However, in the case of a multi-component oxide such as an oxide superconductor, when a thin film is formed by the above-mentioned vacuum deposition method, the vapor pressure of each component is different, so the composition of the thin film obtained by the vapor pressure difference is the evaporation source. The composition of the multi-component oxide is significantly different. Further, during evaporation, the oxide decomposes into a metal element and oxygen, and oxygen necessary for developing superconducting properties escapes from the composition of the thin film, often resulting in a thin film having an oxygen-deficient composition.

Therefore, when a thin film made of a multi-component oxide is formed by the above vacuum deposition method, there is a problem that the composition of the obtained thin film is not uniform and it is difficult to obtain sufficient superconducting properties.

<Object of the Invention> The present invention has been made in view of the above problems, and even if a thin film is formed using a multi-component material, the composition is uniform,
An object of the present invention is to provide a method for manufacturing an oxide superconducting thin film having excellent characteristics.

<Means and Actions for Solving Problems> In order to achieve the above object, the method for producing an oxide superconducting thin film of the present invention is a method for producing an oxide superconducting thin film,
A simple substance or an oxide containing at least one element selected from Ia group elements, IIa group elements and IIIa group elements of the periodic table, at least one element selected from Ib group elements, IIb group elements and IIIb group elements Is vaporized and ionized independently of each other and is irradiated with oxygen ions to form a thin film on the substrate.

According to the method for producing an oxide superconducting thin film having the above-mentioned structure, since a simple substance or an oxide containing a specific element is vaporized independently, an element having the same ratio as the component ratio of the simple substance or the oxide is desired. Reach the substrate at a rate. At this time, when a simple substance made of the above-mentioned specific element is used, the simple substance is vaporized in the presence of oxygen ions, so that oxygen is supplied during thin film formation to form a uniform oxide superconducting thin film. On the other hand, when an oxide containing the above specific element is used,
Even if the oxide is decomposed and oxygen is released during thin film formation, the oxide is vaporized in the presence of oxygen ions, so oxygen is replenished, there is no oxygen deficiency, and there is little defect and uniform and uniform oxide superconductivity. A thin film is formed.

The present invention will be described in detail below.

In the method for producing an oxide superconducting thin film of the present invention, as the thin film forming material, either a simple substance or an oxide may be used as long as it contains an element constituting a superconducting substance. Examples of the element include Ia group elements, IIa group elements and III of the periodic table.
At least one element selected from Group a elements, at least one element selected from Group Ib elements, Group IIb elements and Group IIIb elements, and selected from oxygen, nitrogen, fluorine, chlorine, carbon, and sulfur A simple substance or an oxide containing at least one element is used. More specifically, Periodic Table I
Among the group elements, the group Ia elements include Li, Na, K, Rb and Cs, and the group Ib elements include Cu, Ag and Au.
Is mentioned. Among the Group II elements of the Periodic Table, the Group IIa elements include Be, Mg, Ca, Sr, Ba and Ra, and the Group IIb elements include Zn and Cd. Among the group III elements of the periodic table, examples of the group IIIa elements include Sc, Y, lanthanoid elements such as La, Ce, Gd, and Lu, and actinide elements such as Ac, Th, Pa, and Cf. Also
Examples of the group IIIb element include Al, Ga, In and Tl.

Among the above-mentioned elements, it is preferable to use at least one element selected from the group Ib, at least one element selected from the group IIa, the group IIIa and the lanthanoid series element, and one containing oxygen as a constituent element. Note that Cu is preferable among the elements in Group Ib of the periodic table. Of the elements of Group IIa of the periodic table, Sr or Ba is preferable, and of the elements of Group IIIa of the periodic table, Sc, Y or La is preferable.

The substance containing the above element can be used alone or as an oxide.

The simple substance or oxide containing the above element can be appropriately selected according to the desired characteristics of the thin film.

Then, in the presence of oxygen ions, the above simple substance or oxide is independently vaporized to form a desired thin film on the substrate. The above operation will be described by taking a vacuum evaporation method as an example. In order to independently evaporate the single substance or the oxide (3) toward the substrate (1), the pressure was reduced to a high degree of vacuum as shown in FIG. A plurality of crucibles (2) are independently arranged in the chamber (not shown), and the plurality of crucibles (2) are provided.
In the above, the simple substance or the oxide (3) is individually accommodated, and the individual substances or the oxide (3) accommodated in the crucible (2) are evaporated by heating independently. In this case, the composition of the vaporized simple substance or oxide (3) and the composition of the substrate (1) are vaporized by independently heating each simple substance or oxide (3) under the conditions according to the vapor pressure of each simple substance or the like. The composition of the thin film formed on the substrate can be controlled. The heating conditions and the like can be appropriately selected according to the vapor pressure of the simple substance or the oxide (3) housed in the crucible (2), the growth rate, the film thickness, and the like. Various methods such as an electron beam heating method and an induction heating method can be adopted. The number of crucibles (2) can be appropriately set according to the number of materials required for producing a desired superconductor.

By the above operation, the simple substance or the oxide (3) evaporates toward the substrate (1), but a thin film having a uniform and uniform thin film containing an appropriate amount of oxygen and having excellent characteristics is formed on the substrate. In order to form it on (1), oxygen ions are irradiated toward the substrate (1) together with the above vapor deposition operation to generate a desired oxide superconductor. Irradiation of the oxygen ions,
It can be carried out by ionizing the supplied oxygen molecules with an oxygen ion source (4) by a method such as electric field application and irradiating the substrate (1).

The irradiation dose of the oxygen ions necessary to obtain a thin film having excellent superconducting properties is not only changed depending on the material used as the evaporation source, that is, whether the simple substance is used or an oxide is used. When used, it changes depending on the oxygen content of the oxide. Furthermore, the appropriate irradiation amount of oxygen ions also changes depending on the vapor pressure of the material as the evaporation source, the easiness of decomposing the oxide, and the like. Therefore, the dose of oxygen ions can be appropriately selected according to the above-mentioned material as an evaporation source used.

By performing the oxygen ion irradiation together with the above vapor deposition operation, it is possible to evaporate the element in the same ratio as the element ratio of the simple substance or the oxide toward the substrate, respectively, and since oxygen is supplied by the oxygen ion irradiation, It is possible to obtain a thin film having a uniform composition and excellent characteristics. That is, even if the vapor pressure of the simple substance or oxide used as the evaporation source is different, the heating conditions can be set according to each material, so that it is possible to evaporate at a desired ratio, and the composition of the evaporant can be changed. Can be controlled. Further, even if the oxide is decomposed and oxygen is released, oxygen is supplied by oxygen ion irradiation. Therefore, even if an oxygen-containing substance is used as an evaporation source, the composition of the thin film does not deviate from the composition of the evaporation source, and a thin film having a composition lacking oxygen is not formed, and a uniform and uniform thin film having excellent superconducting properties is formed. can do.

In the above example, when a simple substance is used as an evaporation source, since oxygen ions are irradiated, it is possible to form a thin film having excellent characteristics by simply vaporizing each simple substance independently. In order to obtain a simple oxide superconducting thin film, it is preferable to vaporize each simple substance used independently and to ionize the vaporized simple substance by an ionizer. As a method for ionizing the vaporized elemental element, various methods capable of ionizing a vaporized evaporation source are adopted, and an ion plating method, for example, plasma is formed around the substrate using the substrate as a cathode, and vaporized evaporation is performed. Direct current method of passing a source through plasma, a high frequency method of ionizing using a high frequency coil between a substrate and an evaporation source, a cluster ion beam method and heat of ionizing a vaporized evaporation source using an ionization grid and a hot cathode. The cathode method and the like are exemplified. In this case, as the evaporation source, not only the above simple substance but also the above oxide can be used. In order to produce an oxide superconducting thin film having good characteristics, the method of irradiating oxygen ions, which can constantly supply oxygen ions, is preferable.

Further, in the above, although the simple substance or the oxide is vaporized by the vacuum vapor deposition method, a predetermined element is vaporized by various physical vapor deposition (PVD) methods such as the molecular beam epitaxial method, the sputtering method and the ion plating method. It is also possible to vaporize the contained simple substance or oxide and to irradiate oxygen ions to form an oxide superconducting thin film on the substrate.

In the above thin film manufacturing method, since oxygen ions are supplied,
It is useful for forming an oxide superconducting thin film, and in particular, the oxide superconducting thin film is represented by the following general formula (1) or (2) A _x B _1-x CO ₃ (1) A _y B _2-y CO ₄ (2) (In the formula, A and B represent at least one element selected from the group Ia element, the group IIa element, and the group IIIa element of the periodic table, and C represents the group Ib element, IIb of the periodic table. Group elements and I
At least one element selected from Group IIb elements is shown. ) Is suitable for forming an oxide superconducting thin film represented by the formula (1), and in particular, in the general formula (1) or (2), A and B are elements of Group IIa and IIIa of the periodic table, respectively.
At least one element selected from the group elements, C
Is suitable for forming an oxide superconducting thin film which is an element of Group Ib of the periodic table, especially Cu.

INDUSTRIAL APPLICABILITY The method for producing an oxide superconducting thin film of the present invention is useful for producing an oxide superconducting thin film in which the oxygen content is important in terms of characteristics, and is used in the electronics field for switching elements, memory elements, magnetic flux sensors. It can be applied to the manufacture of amplification elements, etc.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 Using a vacuum vapor deposition apparatus as shown in FIG. 1, La ₂ O ₃ was placed in the crucible (2a) and BaO was placed in the crucible (2b) placed in the chamber.
CuO was housed in each crucible (2c), and the chamber was evacuated to a high vacuum.

In addition, each crucible (2a) (2b) (2c) was heated independently in order to individually adjust the vapor pressure of each of the above materials. That is, the crucible (2a) containing La ₂ O ₃ is 1800K-2000K.
, The temperature of the crucible (2b) containing BaO was in the range of 1300K to 1500K, and the temperature of the crucible (2c) containing CuO was in the range of 1000K to 1300K.

Then, each material as an evaporation source contained in each crucible (2a) (2b) (2c) is independently evaporated toward the substrate (1), and the current density from the oxygen ion source (4) is changed. Oxygen ions were irradiated toward the substrate (1) under the condition of maximum 10 A / m ² to form an oxide superconducting thin film on the substrate (1).

Example 2 The same apparatus as in Example 1 above was used and La was placed in the crucible (2a).
, Ba in the crucible (2b) and Cu in the crucible (2c).

In addition, as in the above embodiment, each crucible (2a) (2b) (2
c) was independently heat-conditioned. That is, the La-containing crucible (2a) has a range of 1400K to 1600K, the Ba-containing crucible (2b) has a range of 500K to 700K, and the Cu-containing crucible (2c).
Was temperature controlled in the range of 1100K to 1200K.

Then, the materials in the respective crucibles (2a) (2b) (2c) are independently evaporated, and in the same manner as in the first embodiment,
The oxide superconducting thin film was formed on the substrate (1) by irradiating the substrate (1) with oxygen ions from the oxygen ion source (4).

When the characteristics of the oxide superconducting thin films obtained in Examples 1 and 2 were examined by an electron microscope and an elemental analyzer, all the oxide superconducting thin films had a uniform and homogeneous composition. In addition, all the oxide superconducting thin films showed excellent electrical characteristics.

<Effects of the Invention> As described above, according to the method for producing an oxide superconducting thin film of the present invention, a simple substance or an oxide containing a specific element is vaporized independently in the presence of oxygen ions, and ionized. In addition to irradiating with oxygen ions to form an oxide superconducting thin film on the substrate, not only the element or the element having the same ratio as the oxide component ratio is vaporized but also oxygen is replenished when the thin film is formed. As a result, it is possible to form an oxide superconducting thin film having a uniform and homogeneous composition without oxygen deficiency.

[Brief description of drawings]

The figure is a schematic diagram showing an outline of a vacuum vapor deposition apparatus. (1) ... substrate, (2) (2a) (2b) (2c) ... crucible,
(3) (3a) (3b) (3c) ... simple substance or oxide, (4)
… Oxygen ion source

Claims (4)

[Claims] 1. A method for producing an oxide superconducting thin film, comprising at least one element selected from Group Ia, Group IIa and Group IIIa, Ib, Group IIb and Group IIIb elements in the periodic table. A single oxide or oxide containing at least one selected element is independently vaporized and ionized, and oxygen ions are irradiated to form a thin film on a substrate. Production method. 2. An oxide superconducting thin film has the following general formula (1) or (2) A _x B _1-x CO ₃ (1) A _y B _2-y CO ₄ (2) (wherein A, B Are at least one element selected from Group Ia element, Group IIa element and Group IIIa element of the periodic table, respectively, and C is an element of Group Ib, Group IIb and Group I of the periodic table.
At least one element selected from Group IIb elements is shown. The manufacturing method of the oxide superconducting thin film of Claim 1 represented by the said. 3. A and B are at least one element selected from Group IIa elements and Group IIIa elements of the Periodic Table, and C is at least 1 selected from Group Ib elements of the Periodic Table.
The method for producing an oxide superconducting thin film according to claim 2, which is a seed element. 4. A group IIa element of the periodic table is Sr or Ba, and I
The method for producing an oxide superconducting thin film according to claim 3, wherein the IIa group element is Sc, Y or La and the Ib group element is Cu.