JP2748457B2 - Superconducting film manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for producing a layered perovskite-type superconducting film containing Bi and Pb, and relates to a superconductor having a structure in which the number of Cu-O planes is three in a 1/2 unit cell. In order to form a superconducting film having a high critical temperature and a high critical current density by firing in a short time, the Bi-containing element containing a Bi-based oxide superconductor having a layered perovskite structure on a substrate is included. (Pb) -Sr-Ca-Cu
A plurality of steps of forming a -O composite oxide layer, and a first element constituting the Bi-based oxide superconductor or an oxide thereof, or an accelerator for forming the Bi-based oxide superconductor A second element or its oxide that acts, with a vapor pressure of 800 ° C
The compensation layer containing a high concentration of the first and / or the second element or the oxide thereof at 10 ^-4 Pa or more in the Bi-
At least one step of forming adjacent to the (Pb) -Sr-Ca-Cu-O composite oxide layer, and the Bi- (Pb) -Sr-Ca-Cu
A step of baking the substrate on which the laminated structure of the -O composite oxide layer and the compensation layer are formed in an oxidizing atmosphere containing oxygen, wherein a method for producing a superconducting film (however, Bi- (Pb) -Sr-Ca -Cu-O is
Represents a composite oxide containing or not containing Pb).

[Industrial applications]

Research and development of high-temperature superconducting materials capable of achieving superconductivity at the temperature of liquid nitrogen have been rapidly advanced, and practical technologies using the same have been developed.

High-temperature superconductors with a critical temperature Tc exceeding 100 K can have a wide temperature margin for application of liquid nitrogen temperature, critical current density J
c, the critical magnetic field Hc rises in principle, the application of thin films and wires,
Research and development are proceeding from the viewpoint of the possibility of high temperature superconducting materials with higher Tc.

As a high-temperature superconducting material whose critical temperature Tc exceeds 100K, Bi
-Sr-Ca-Cu-O-based superconductors and Tl-Ba-Ca-Cu-O-based superconductors have been developed.

In the above Bi system, the critical temperature Tc is a low temperature phase of about 80 K, and about 110 K
In the above Tl system, a critical phase Tc of about 105K is mixed with a low-temperature phase of about 105K, and a plurality of superconducting phases of about 125K are mixed. It cannot be taken out alone.

The Bi-based and Tl-based systems are characterized by being hardly affected by water or oxygen, easy to produce, easy to process, and hardly restricted by resources because they do not contain rare earth elements. However, it is easy to produce a low Tc phase, but it is difficult to make a high Tc phase a single phase.

Bi-Sr-Cu-O-based superconductors are described in Michel et al. (Z. Phys. B68, 1
987, 421) and Akimitsu et al. (Jpn. J. Appl. Phys. 26, 1987, L20
80). The Tc of this system is 7K.

Maeda et al. (Jpn.J.Appl.Phys.27,1988, L209)
High Tc phase Bi-Sr-Ca-Cu-O system was discovered. This system has the formula
In Bi ₂ Sr ₂ C a _n-1 C _n O _x , there are three more phases: a phase of Tc = 7K for n = 1, a phase of Tc = 80K for n = 2, and a phase of Tc = 105K for n = 3. It has been found to have a conducting phase. As n increases from 1 to 3, the number of CuO layers in the crystal structure increases, and the c-axis changes from 24 ° to 30 °, 3 °.
Changes to 7Å.

Takano et al. (Jpn. J. Appl. Phys. 27, 1988, L1041) Bi to Pb
It has been reported that the substitution with increases the proportion of the high Tc phase. However, the role of Pb is not yet clear.

As described above, establishment of a process for making the high Tc phase of the Bi- (Pb) -Sr-Ca-Cu-O-based superconductor or the Tl-Ba-Ca-Cu-O-based superconductor into a single phase has been established. Requested.

(Prior art)

For example, as a method of manufacturing a superconducting film of Bi-Sr-Ca-Cu-O, an oxide is deposited on a substrate such as SrTiO ₃ or MgO by a sputtering method, a vapor deposition method or the like, and then deposited and oxidized by a heat treatment. A method of reacting a film to obtain a superconducting film is generally used.

[Problems to be solved by the present invention]

The layered perovskite-type superconducting film has four or more metal elements, and it has been difficult to adjust the composition ratio of each to the stoichiometric composition. In addition, Bi and Pb, which have relatively high vapor pressures, are liable to be lost from the film due to evaporation of a part of the film during deposition, and the amount of the loss varies depending on the substrate temperature, the deposition rate of the film, etc. And it was difficult to form a film with reproducibility.

The vapor pressure (P) of an element or oxide is generally represented by the following equation. log P = AT ^-1 + B log T + C * 10 ^-3 * T + D (Metal Data Handbook p86) T: Examples of vapor pressures of elements and oxides at an absolute temperature (K) of 1073K (800 ° C) are as follows: .

FIG. 4 shows a substrate on a MgO substrate using a fired body target of oxide of Bi: Sr: Ca: Cu = 2: 2: 2: 3 (fired oxide mixture at 800 ° C. for 24 hours in air atmosphere). FIG. 4 is a diagram showing an X-ray diffraction pattern and a film composition when a sputtered film (thickness: 1 μm) is baked at 875 ° C. for 5 hours by RF magnetron sputtering at a temperature of 400 ° C. under a reduced pressure of 1 Pa. As shown in the X-ray diffraction pattern, the film was composed of _two phases, Bi ₂ Sr ₂ CuOx and a low Tc phase Bi ₂ Sr ₂ CaCu ₂ Ox of 80K class.

Also, as shown by the measurement results by the electron probe microanalysis (EPMA) method, Bi: Sr: Ca: Cu = 0.63: 1.00: 1.0
7: 1.40, so-called high-temperature phase (Bi ₂ Sr ₂ Ca ₂ Cu ₃ Ox) with Bi less than the target composition and having a critical temperature near 110K
It can be seen that the stoichiometry greatly deviates from the stoichiometry.

When Pb is put into a film having such a stoichiometric deviation, that is, using a sintered target of Pb-doped oxide of Bi: Pb: Sr: Ca: Cu = 2: 0.4: 2: 2: 3 When calcination is carried out in the same manner as above (calcination in air at 850 ° C. for 12 hours), a high-temperature phase appears but the amount is not large (FIG. 5). As shown in FIG. 6, the temperature change of the electric resistance was onset at around 110 K, but it fell below the low temperature side, and the electric resistance became zero, which was as low as 75 K.

Generally, in the bulk, when a proper amount of Pb is added to Bi-Sr-Ca-Cu-O, a relatively large amount of a high-temperature phase can be obtained.
et al. (JJAPL.VoL27, pp-L1861-
L1863) However, Pb was easily evaporated during film formation, so that a sufficient amount of Pb could not be added by sputtering or vapor deposition.

The present invention has been made in view of such conventional problems, and among the elements constituting the layered perovskite structure, oxides of elements having a high vapor pressure and difficult to deposit, for example, Bi ₂ O ₃ , Pb
For O, a layer containing them at a high concentration is provided in the deposited film, and the composition ratio of the entire film approaches the stoichiometric composition, and Cu-O
It is an object of the present invention to provide a method for forming a superconducting film including a superconductor having a structure in which three planes are contained in a half unit cell and having a high critical temperature and a high critical current density by firing in a short time. Aim.

[Means for solving the problem]

The present invention relates to a Bi having a layered perovskite structure on a substrate.
Bi- (Pb) -Sr containing the elements that make up the system oxide superconductor
A plurality of steps of forming a -Ca-Cu-O composite oxide layer,
A first element or an oxide thereof constituting the Bi-based oxide superconductor, or a second element or an oxide thereof acting as an accelerator in the formation of the Bi-based oxide superconductor, and having a vapor pressure said first and / or said second element or compensating layer containing the oxide in a high concentration the Bi- (Pb) -Sr-Ca- Cu-O composite but to be 10 ^-4 Pa or more at 800 ° C. At least one step of forming adjacent to the oxide layer; and forming the Bi- (Pb) -Sr-
A step of firing the substrate on which the stacked structure of the Ca—Cu—O composite oxide layer and the compensation layer is formed in an oxidizing atmosphere containing oxygen. (However, Bi- (Pb) -Sr-Ca-Cu
(-O represents a complex oxide containing or not containing Pb) When the above heat treatment is performed at a temperature of 750 ° C to 890 ° C, a high Tc phase superconductor is not formed at a temperature lower than 750 ° C.
At temperatures higher than ℃, the superconductor melts and decomposes.

The oxide having a vapor pressure of 10 ⁻⁴ Pa or more at 800 ° C. is defined as an oxide that forms a perovskite superconductor at the heat treatment temperature or acts as a promoter in superconductor formation. Evaporation of oxide elements or oxides is remarkable, and compositional fluctuations or compositional changes are remarkable. Compensation and addition of evaporated components are required to form a stoichiometric high-Tc superconductor. It is.

The perovskite-type superconducting material has the general formula Bi ₂ (Sr
_1-x Ca _x ) _m Cu _n Oz Is a superconducting material represented by

(The low Tc phase is said to have a composition close to m = 3, n = 2; the high Tc phase is said to have a composition close to m = 4, n = 3.) Alternatively, the perovskite-type superconducting material is one of the above superconducting materials. The superconducting substance was obtained by replacing parts by Pb and by adding Pb.

The oxide is Bi ₂ O ₃ or PbO.

As an example of the step, an oxide deposition layer containing an element constituting a superconductor having a layered perovskite structure is formed on a substrate by sputtering, vapor deposition, molecular beam epitaxial growth, or the like at a first temperature (T ₁ ) And then heat treating the oxide deposited layer in a oxidizing atmosphere containing oxygen at a second temperature (T ₂ ) higher than the _first temperature (T ₁ ) to form a layered perovskite structure In a method for manufacturing a superconductor film having a step of forming a superconductor layer, the oxide deposited layer has a laminated structure, and the (first temperature or For an oxide having a high vapor pressure at the second temperature, at least one compensation layer containing a high concentration of the oxide is provided, and after the heat treatment at the _second temperature (T ₂ ), the entire film is formed. Acid having a composition ratio of the above-mentioned layered perovskite structure Characterized by composition control such that the stoichiometric composition of the object superconductors.

More specifically, a step of forming a first layer of a composite oxide containing an element constituting the superconductor having the layered perovskite structure on a substrate, A step of forming a second layer containing a high concentration of an oxide having a pressure of 10 ⁻⁴ Pa or more at 800 ° C. and a step of firing the substrate having the stacked structure in an oxidizing atmosphere containing oxygen. Configure.

Note that the stacked structure of the oxide deposition layer may be a stacked structure in which the composition changes stepwise or a stacked structure in which the composition changes in a graded manner with respect to a specific constituent element. Good.

In addition, as a method of depositing an oxide deposited layer, there are a plasma method, a physical vapor deposition method such as sputtering, evaporation, MBE, etc.
A chemical vapor deposition method or the like may be used.

The stacking order of the stacked structure of the oxide deposited layer is such that a Bi—Sr—Ca—Cu—O composite oxide layer is formed immediately above a substrate (MgO or the like) in order to ensure adhesion between the film and the substrate. It is preferable that the uppermost layer of the laminated structure is a Bi-Sr-Ca-Cu-O composite oxide layer in order to prevent evaporation of the oxide having a high vapor pressure.

In addition, the stacked structure of the oxide deposition layer contains a high concentration of an oxide having a high vapor pressure among oxides of elements constituting a superconductor or oxides containing an element acting as a promoter in superconductor formation. A structure in which a layer to be sandwiched is sandwiched between layers of a Bi—Sr—Ca—Cu—O-based composite oxide (or a mixture of the respective oxides) may be a structure that is repeatedly deposited one or more times and a plurality of times.

[Action]

In the present invention, of the elements constituting the layered provskite structure, only oxides of elements having a high vapor pressure and which are difficult to deposit are concentratedly deposited in the film, so that the deposition time of these layers can be reduced. The change in composition due to evaporation during deposition can be neglected. In addition, by depositing an oxide which hardly evaporates immediately thereon, evaporation during the deposition of the entire film can be suppressed to a very small amount.

As a result, the film composition can be very strictly controlled, and thus, by optimizing the composition, high Tc and high Jc can be achieved.

〔Example〕

FIG. 1 shows the layer structure of a thin film deposited according to the invention. This is an example of the Bi-Sr-Ca-Cu-O system doped with Pb.

The result of the composition analysis of the film baked at 850 ° C. for 1 hour after the deposition is Bi: Pb: Sr: Ca: Cu = 0.87: 0.34: 1.00: 1.27: 1.88. It turns out that it was doped inside.

FIG. 2 shows the temperature change of the electric resistance of the film after firing. Tc
It showed a sufficiently high critical temperature of e = 106.5K.

FIG. 3 shows the characteristics when the temperature change of the electric resistance is observed while changing the current density. At liquid nitrogen temperature, 2.
Sufficient characteristics of 4 × 10 ³ A / cm ² were obtained.

That is, FIG. 1 shows a laminated structure of thin films deposited according to an embodiment of the present invention.

The thin film laminated structure is formed on a MgO single crystal (100) substrate by RF magnetron sputtering under the following conditions with Bi-Sr-Ca
A -Cu-O layer (hereinafter referred to as a BSCCO layer) was deposited.

The MgO substrate is heated to about 400 ° C. Ar: O ₂ = 1: 1,1Pa, RF power is 100W (about 1.3W / cm ² ) Target is (1) Sintered body of Bi ₂ Sr ₂ Ca ₂ Cu ₃ Oz composition Target I (80
(2 hours) Bi ₂ Pb _0.4 Sr ₂ Ca ₂ Cu ₃ O doped with about 20% of Bi
Sintered body target II of z composition (sintering at 800 ° C for 24 hours) (3) Bi ₂ O ₃ target III for Bi compensation (4) PbO target IV for Pb addition was used.

[Comparative Example 1] First, in order to determine how much Bi should be compensated, a thin film was formed into a single BSCCO sintered target I (Bi: Sr: Ca:
(Cu = 2: 2: 2: 3 target composition), deposited on a MgO substrate heated to 400 ° C. to a thickness of about 1 μm by a single layer method, and then heat-treated at 875 ° C. for 5 hours in air. .

The X-ray diffraction pattern of the heat-treated sample is shown in FIG.
As shown in FIG. 4, after baking at 875 ° C. for 5 hours, Tce is 10K.
Low Tc of Bi ₂ Sr ₂ CuOx and Bi ₂ Sr ₂ CaCu ₂ Ox of 80K class
A phase is formed.

The thin film composition determined by the EPMA method is, as shown in FIG. 4, the composition of the target (Bi: Sr: Ca: Cu = 2: 2: 2: 3)
The composition of the thin film (Bi: Sr: Ca: Cu = 0.63: 1.00: 1.07:
As shown in 1.40), the decrease of Bi is remarkable.

Comparative Example 2 Single Pb-doped BSCCO sintered target II (Bi: Pb: Sr:
(Ca: Cu = 2: 0.4: 2: 2: 3 target composition), deposited on a MgO substrate heated to 400 ° C to a thickness of about 1 μm by a single layer method, and then heat-treated at 850 ° C for 12 hours in air Thus, a superconductor film was formed.

FIG. 5 shows the X-ray diffraction pattern. As shown in the X-ray diffraction pattern of FIG. 5, the ratio of the high Tc phase of the thin film is smaller than that of the low Tc phase even after firing at 850 ° C. for 12 hours.

FIG. 6 shows the temperature dependence of the electric resistance. The onset temperature is over 100K, but Tce is 75K.

The thin film composition was determined by the EPMA method. The films are Bi-deficient and non-stoichiometric. Also, it was found that only a small amount of Pb was doped in the thin film, which was insufficient for forming a high Tc phase.

Example 1 _{BSCCO (Bi 2 Sr 2 Ca 2} Cu 3 Oz) sintered target I composition
And Bi ₂ O ₃ target III, 40
On a MgO substrate heated to 0 ° C, Bi-Sr-Ca-
Deposited by Cu-O layers and Bi ₂ O ₃ layer a magnetron sputtering method.

BiSrCaCuO layer: 2000 mm thick, 4 layers Bi ₂ O ₃ layer: 150 mm thick, 3 layers stacked structure, deposited to a total thickness of about 1 μm.

Thereafter, annealing was performed in air at 875 ° C. for 5 hours. The thin film thus formed was analyzed for composition by EPMA,
Can be adequately compensated and the composition is found to be very close to the stoichiometric composition of the high Tc phase.

However, according to the X-ray diffraction pattern of the thin film,
The Tc phase was found to be barely detectable.

Example 2 400 ° C. by RF magnetron sputtering using _three targets of a sintered body target I having a BSCCO composition (Bi ₂ Sr ₂ Ca ₂ Cu ₃ Oz), a Bi ₂ O ₃ target III and a PbO target IV. Bi-Sr- on a MgO substrate heated by
The steps of sequentially depositing a Ca—Cu—O layer, a Bi ₂ O ₃ layer, and a PbO layer were repeated to form an oxide deposited multilayer structure shown in FIG.

Each layer thickness of the BiSrCaCuO layer 3000Å, Bi ₂ O ₃ layers each layer thickness of 20
The PbO layer was deposited so as to have a thickness of 0 ° and a thickness of 100 °, and the thickness of the entire laminated structure was about 1 μm. (Note, Bi-Sr-Ca-Cu -O layers, Bi ₂ O ₃ layer, the thickness of the PbO layer, the number of stacked, layered structure, the heat treatment temperature, heat treatment time, taking into account the film composition of interest, appropriately selected・ Controlled.) Thereafter, firing was performed at 850 ° C. for a predetermined time (10 minutes to 15 hours) in the atmosphere.

In the multilayer deposition method of the present invention, as the thin film continues to be heat-treated and baked, more Pb evaporates and 85
After 3 hours at 0 ° C., it was found that only a small amount of Pb remained in the thin film. During the calcination at 850 ° C. for 10 minutes, the oxide film, which was amorphous after deposition, reacted, and one third of the film was in the high Tc phase. After firing for 1 hour, more than 1/2 had a high Tc phase. 1
After calcination for 5 hours, only a small amount of Pb remained, but most of the thin film had a high Tc phase. This suggests that Pb promotes high Tc phase formation, but high Tc phase does not always require Pb.

According to the method of the present invention, Bi ₂ O ₃ , PbO
The temperature dependence of the electrical resistance of the thin film obtained by stacking a Bi ₂ O ₃ layer and a PbO layer for compensating for evaporation during the heat treatment and repeatedly stacking these layers is as shown in FIG. is there. The electric resistance decreases linearly with temperature, and decreases rapidly near 110K. Tce after firing for 10 minutes
The value was 94.5K, and the Tce value after firing for 1 hour was 106.5K. For a 15 hour bake, the onset temperature will be slightly higher. However, the Tce values turned out to be almost the same.

As described above, using a conventional single-fired target (target composition Bi ₂ Sr ₂ Ca ₂ Cu ₃ Oz), a thin film is deposited on a substrate such as MgO by RF magnetron sputtering, and then oxygen When heat treatment is performed in an atmosphere, the formed thin film lacks Bi and has a non-stoichiometric composition. Also high Tc
Single sintered target (target composition Bi ₂ Pb _0.4 Sr ₂ Ca ₂ Cu ₃ O) doped with Pb, which is said to promote phase formation
The thin film formed in the same process using z) has a short stoichiometric composition due to a shortage of Bi. In addition, sufficient Pb for high Tc phase formation
Cannot be deposited. As a result, the conventional thin film formed by the single-layer method using a single target has a multi-phase, and the single-phase of the high Tc phase superconductor cannot be achieved. The high Tc phase is small even if it is formed.

On the other hand, the sintered target (target composition Bi ₂ S) used for depositing the composite oxide layer containing the element constituting the superconductor having the layered perovskite structure of the present invention is used.
r ₂ Ca ₂ Cu ₃ Oz, Bi ₂ Pb _0.4 Sr ₂ Ca ₂ Cu ₃ Oz), among the elements that make up the superconductor, such as Bi ₂ O ₃ , the layer deposition temperature or the deposited layer annealing temperature Vapor pressure is high under the conditions, and in such a processing step, a compensating component target (such as Bi ₂ O ₃ ) used for depositing a compensating layer that compensates for a component that evaporates and becomes insufficient from the superconductor composition. Although it is not an essential component as a high Tc phase component of the superconductor, it has an action to promote the generation of a high Tc phase, but has a high Tc phase content such as PbO which is easily evaporated at the temperature conditions of the layer deposition step or the heat treatment step of the deposited layer. The high level used to deposit layers that provide a sufficient supply of Tc phase formation promoting components
Bi-component can be appropriately compensated by the multilayer method of the present invention in which multiple targets such as a target for Tc phase generation promoting component (such as PbO) are deposited on a substrate in multiple layers and then heat-treated and annealed. The composition of the superconductor film to be formed can be a stoichiometric composition.

Sufficient Pb to promote high Tc phase formation in superconductors
Can be doped.

As described above, the composition of the formed thin film is
It can approach the stoichiometric composition of the Tc phase and can be sufficiently doped with Pb, which acts as an accelerator for the generation of a high Tc phase, so that it can exhibit a high-quality high Tc phase in a very short heat treatment. A superconductor film can be formed.

(Effect of the present invention)

As described above, according to the present invention, Bi, P which evaporates from the film during film deposition, is defective, or cannot be sufficiently added.
The layered perovskite type, which has a sufficiently high critical temperature and a sufficiently high critical current density, even if it is fired for a short time, can be strictly controlled in the composition of elements such as b, and precisely adjusted to the composition for generating a high-temperature phase. A superconducting film can be formed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a laminated structure of an oxide deposition layer in one embodiment of the present invention, and FIG. 2 is a temperature dependence of electric resistance of a superconductor film manufactured according to the present invention. FIG. 3 is a diagram showing the temperature dependence of the electric resistance when the current density of the superconductor film manufactured according to the present invention is changed. FIG. 4 is a single BSCCO sintered body according to the conventional method. Target I
FIG. 5 is a view showing an X-ray diffraction pattern of a film manufactured by using the method. FIG. 5 is a view showing an X-ray diffraction pattern of a film manufactured by using a single Pb-doped BSCCO sintered body target II according to a conventional method. FIG. 4 is a diagram showing the temperature dependence of the electrical resistance of a film manufactured using a single Pb-doped BSCCO sintered target II according to a conventional method.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-44029 (JP, A) JP-A-2-97427 (JP, A)

Claims (11)

(57) [Claims] 1. A substrate having a layered perovskite structure on a substrate
Bi- (Pb)-containing elements that make up Bi-based oxide superconductors
A plurality of steps of forming an Sr—Ca—Cu—O composite oxide layer, a first element constituting the Bi-based oxide superconductor or an oxide thereof, or the Bi-based oxide superconductor A second element or an oxide thereof that acts as a promoter in the formation of the first and / or the second element or an oxide thereof having a vapor pressure of 10 ^-4 Pa or more at 800 ° C. At least one step of forming a compensating layer containing the Bi- (Pb) -Sr-Ca-Cu-O composite oxide layer adjacent to the Bi- (Pb) -Sr-Ca-Cu-O composite oxide layer;
A method for producing a superconducting film, comprising a step of firing a substrate on which a laminated structure of an Sr-Ca-Cu-O composite oxide layer and a compensation layer is formed in an oxidizing atmosphere containing oxygen. (However,
Bi- (Pb) -Sr-Ca-Cu-O represents a composite oxide containing or not containing Pb.) 2. The Bi- (Pb) -Sr-Ca-Cu-O composite oxide layer or the compensation layer is formed by sputtering, vapor deposition, physical vapor deposition of MBE, plasma, or chemical vapor deposition. The method for producing a superconducting film according to claim 1, wherein 3. A method for producing a superconducting film according to claim 1, wherein said calcination is carried out at a temperature of 750 ° C. to 890 ° C. in the atmosphere or in an atmosphere having an oxygen partial pressure of 1 atm or less. . 4. A sintered body target of a Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _z composition, wherein the Bi— (Pb) —Sr—Ca—Cu—O composite oxide layer is
RF using sintered target of Bi ₂ Pb _0.4 Sr ₂ Ca ₂ Cu ₃ O _z composition
2. The method for producing a superconducting film according to claim 1, wherein the superconducting film is formed by magnetron sputtering. 5. The method according to claim 1, wherein said compensation layer is made of PbO, Pb, Bi ₂ O ₃ , Bi. 6. The method according to claim 1, wherein said compensation layer is a Bi ₂ O ₃ layer and is formed by RF magnetron sputtering using a Bi ₂ O ₃ target. 7. The method according to claim 1, wherein the compensation layer is a PbO layer and is formed by RF magnetron sputtering using a PbO target. 8. The composite oxide layer according to claim 1, wherein the Bi- (Pb) -Sr-Ca-Cu-O composite oxide layer is formed immediately above the substrate and on the uppermost layer of the laminated structure. The method for producing a superconducting film according to the above. 9. The method according to claim 1, wherein the Bi- (Pb) -Sr-Ca-Cu-O composite oxide layer and / or the compensation layer are formed on a substrate heated to a temperature lower than the firing temperature. 9. The method for manufacturing a superconducting film according to claim 1-8. 10. A patent wherein the Bi- (Pb) -Sr-Ca-Cu-O composite oxide layer and / or the compensation layer is formed on a MgO single crystal substrate heated to 400 ° C. A method for manufacturing a superconducting film according to claim 9. 11. The Bi-based oxide superconductor of the general formula Bi ₂ (S
r _1-x Ca _x ) _m Cu _n O _z [where 0 <x <1, (m = 3, n = 2) or (m = 4, n = 3), 0 <z] The method for producing a superconducting film according to claim 1, wherein the method is a conductive material.