JP2000095518A - Fine oxide superconductor structure and its formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a fine oxide superconductor structure of sub-micron size while preventing the deterioration of superconducting characteristics by forming projections on a substrate or recesses in the substrate and forming oxide superconductor films on the tops of the projections or the bottoms of the recesses or on the side walls of the projections or recesses. SOLUTION: The plane shape of the projections or recesses or the shape of the side walls of the projections or recesses is made almost equal to a pattern formed with an oxide superconductor film. The size of the objective fine structure comprising oxide superconductor films can be reduced to a sub-micron level by reducing the plane shape size or side wall size of the projections or recesses to a sub-micron level. The height from the surface of the substrate to the tops of the projections and the depth from the surface of the substrate to the bottoms of the recesses may be <=1.0 μm, When the plane shape of the tops or bottoms are made polygonal, Josephson coupling is easily formed by utilizing the angular parts. An electrode of a capacitor and SIS joint of a conductor are easily formed by adjusting the plane shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconductor microstructure and a method for forming the same.
The present invention relates to an oxide superconductor microstructure capable of preventing deterioration of superconducting characteristics and a method for forming the same.

[0002]

2. Description of the Related Art In recent years, it has been reported that an oxide sintered body exhibits superconductivity at a high critical temperature, and the practical use of superconductivity technology using this oxide superconductor has been promoted. For example, it has been reported that bismuth-based oxides exhibit superconductivity at 110K. Since these oxide superconductors exhibit superconducting properties in relatively inexpensive liquid nitrogen, their practical use is expected.

One of the fields of application of such oxide superconductors is
For example, application to wiring of a semiconductor device is being studied. Therefore, there is a demand for a fine processing technique for processing the oxide superconductor into wiring and other desired shapes. Such fine processing techniques include lithography techniques such as photolithography and electron beam lithography,
2. Description of the Related Art There is known a technique of performing fine processing in combination with an etching technique such as argon ion etching or chemical etching. Techniques for directly processing an oxide superconductor into a desired shape, such as focused ion beam processing and laser etching, have also been used. The use of these techniques has enabled microfabrication of oxide superconductors in a micron size.

[0004]

By processing an oxide superconductor thin film using such a fine processing technique, wirings, oxide superconductor elements, and oxide superconductor Josephson elements are formed. That is being considered. In order to realize these, considering that the Josephson magnetic field penetration length is about 1 μm, a fine processing technique capable of processing an oxide superconductor thin film with submicron or less precision is required.

Here, if an electron beam lithography technique and a dry etching technique, which are techniques conventionally used in a semiconductor device manufacturing process, are used in combination, as shown in FIG. 23, a wiring having a width of 100 nm or less is formed. It is possible to form a fine structure of an oxide superconductor such as. Here, FIG. 23 is a schematic cross-sectional view of an oxide superconductor fine structure formed using an electron beam lithography technique and a dry etching technique.

Referring to FIG. 23, an oxide superconductor microstructure comprises a substrate 101 and a wiring 10 made of an oxide superconductor.
3a. The wiring 103a is formed on the substrate 101. The line width of the wiring 103a is about 100 nm.

FIGS. 24 to 26 are schematic sectional views showing a method of forming the oxide superconductor fine structure shown in FIG.
With reference to FIGS. 24 to 26, a method for forming an oxide superconductor fine structure will be described.

Referring to FIG. 24, a thin film 103 made of an oxide superconductor is formed on a substrate 101. This thin film 10
3 is formed with a resist film 107.

Next, a resist pattern is drawn on the resist film using an electron beam. Then, by subjecting the resist film 107 to a developing process, a resist pattern 107a is formed as shown in FIG.

Next, as shown in FIG. 26, using the resist pattern 107a as a mask, the thin film 103 is removed by dry etching to form a wiring 103a made of an oxide superconductor.

Thereafter, by removing the resist pattern 107a, an oxide superconductor fine structure as shown in FIG. 23 is obtained.

However, in the above forming method, FIG.
5 and 26, the oxide superconductor thin film 10
3, the side surfaces 108a and 108b of the wiring 103a made of an oxide superconductor are thermally or chemically damaged due to the etching. The superconductivity of the damaged oxide superconductor deteriorates.

The size of the region of the oxide superconductor damaged by the etching as described above is determined by the wiring 1
Even if the line width of 03a becomes small, it hardly changes. Therefore, as the line width of the wiring 103a decreases, the ratio of the region damaged by the etching to the entire wiring 103a increases. Here, when the line width of the wiring 103a was larger than about 1 μm, the ratio of the region where the superconducting characteristics were deteriorated due to the damage due to the etching was relatively small and did not pose a problem. However, when the line width of the wiring 103a is set to be equal to or less than submicron, the ratio of the region where the superconductivity is deteriorated due to the damage to the entire wiring 103a becomes large and cannot be ignored. Therefore, when forming an oxide superconductor microstructure having a size of submicron or less, there is a problem that required superconducting characteristics cannot be obtained. As a result, the lower limit of the size that can be processed without deteriorating the superconductivity in the fine processing of the oxide superconductor using the above-described conventional technology is about 1 μm.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and one object of the present invention is to form a submicron-sized fine structure while preventing deterioration of superconducting characteristics. It is an object of the present invention to provide a possible method for forming an oxide superconductor microstructure.

Another object of the present invention is to provide an oxide superconductor microstructure in which deterioration of superconductivity does not occur.

[0016]

In one aspect of the present invention, a method for forming an oxide superconductor microstructure includes forming a convex or concave portion on a substrate. An oxide superconductor film is formed on the top surface of the projection or the bottom surface of the depression (claim 1).

Here, the oxide superconductor film is easily damaged by etching or processing using a focused ion beam or the like, and its superconductivity is likely to deteriorate. Therefore, by making the planar shape of the convex or concave portion substantially the same as the predetermined pattern formed by the oxide superconductor film, direct processing such as etching and focused ion beam processing can be performed on the oxide superconductor film. A structure having a predetermined shape by the oxide superconductor film can be obtained without performing the application.
Further, since the oxide superconductor film is not subjected to direct processing such as etching, it is possible to prevent the oxide superconductor film from being thermally or chemically damaged due to the etching or the like. As a result, it is possible to prevent the superconducting properties of the oxide superconductor film from deteriorating due to these damages.

Further, by setting the planar shape size of the projections or depressions to the submicron level, the size of the microstructure formed of the formed oxide superconductor film can also be set to the submicron level. As a result, a submicron oxide superconductor fine structure can be formed without deteriorating superconducting characteristics.

In another aspect of the present invention, a method for forming an oxide superconductor microstructure includes forming a convex portion or a concave portion on a substrate. An oxide superconductor film is formed on the side wall of the projection or the recess (claim 2).

Therefore, by making the shape of the side wall of the convex portion or the concave portion substantially the same as a predetermined pattern formed by the oxide superconductor film, the oxide superconductor film can be directly formed by etching or focused ion beam processing. It is possible to obtain a structure having a predetermined shape by the oxide superconductor film without performing any special processing. Further, since the oxide superconductor film is not subjected to direct processing such as etching, it is possible to prevent the oxide superconductor film from being thermally or chemically damaged due to the etching or the like. As a result, it is possible to prevent the superconducting properties of the oxide superconductor film from deteriorating due to these damages.

Further, by setting the size of the side wall of the projection or the recess to the submicron level, the size of the microstructure formed of the formed oxide superconductor film can also be set to the submicron level. As a result, a submicron oxide superconductor fine structure can be formed without deteriorating superconducting characteristics.

In the method for forming an oxide superconductor microstructure according to one aspect or another aspect, the height from the surface of the substrate to the top surface of the projection may be 1.0 μm or less. ).

In the method for forming a fine structure of an oxide superconductor according to the first aspect or the other aspect, a depth from a surface of the substrate to a bottom surface of the concave portion may be 1.0 μm or less.

In the method of forming an oxide superconductor microstructure according to one aspect or another aspect, the top surface or the bottom surface may have a polygonal planar shape.

Therefore, the Josephson junction can be easily formed by utilizing the polygonal corners, and thus the Josephson element can be easily formed. Also,
By adjusting the planar shape, the SIS junction of the electrode of the capacitor and the conductor can be easily formed.

In the method of forming an oxide superconductor fine structure according to the above aspect or another aspect, the length of one side of the polygon may be 1.0 μm or less.

Therefore, miniaturization and integration of the device using the oxide superconductor can be more easily performed.

In the method for forming a fine structure of an oxide superconductor according to one aspect or another aspect, the top surface or the bottom surface may have a linear planar shape.

Therefore, it is possible to easily form a wiring or a microwave transmission line made of an oxide superconductor.

[0030] In the method for forming an oxide superconductor microstructure according to the one aspect or the other aspect, the line width may be 1.0 μm.
m or less (claim 8).

In the method for producing a fine structure of an oxide superconductor according to one aspect or another aspect, the substrate may contain strontium titanate.

Therefore, an oxide superconductor film can be formed on a substrate containing strontium titanate, so that an oxide superconductor film having excellent superconductivity can be obtained.

In the method for forming an oxide superconductor microstructure according to one aspect or the other aspect, when the side wall of the projection or the recess is expressed by a Miller index, the strontium titanate has a [100] direction or a [110] direction. (Claim 10).

Here, on a plane substantially parallel to the [100] and [110] directions of strontium titanate represented by the Miller index, an oxide superconductor film having excellent characteristics can be epitaxially grown. As a result,
An oxide superconductor microstructure including an oxide superconductor film having excellent superconductivity can be easily obtained.

In the method for forming an oxide superconductor microstructure according to one aspect or the other aspect, the step of forming the oxide superconductor film includes the step of forming the oxide superconductor film using molecular beam epitaxy. (Claim 11).

Here, in the molecular beam epitaxy method, a film is formed on a substrate by irradiating the substrate with a molecular beam containing an element to be a material of a film to be formed. At this time, the irradiation directions of the plurality of molecular beams can be independently controlled. Therefore, the surface on which the oxide superconductor film is formed and the crystal orientation of the oxide superconductor film can be easily controlled. As a result, an oxide superconductor film having excellent superconductivity can be easily formed. As a result, an oxide superconductor microstructure having excellent superconducting properties can be obtained.

In the method for forming an oxide superconductor microstructure according to one aspect or the other aspect, the step of forming an oxide superconductor film using a molecular beam epitaxy method includes the steps of: The method may include a step of adjusting an incident direction with respect to the surface (claim 12).

Since the oxide superconductor has particularly strong anisotropy, it is necessary to adjust the crystal orientation to a specific direction with respect to the direction of current flow. Therefore, the crystal orientation of the oxide superconductor film can be controlled by adjusting the incident direction of the molecular beam on the substrate surface. Thereby, an oxide superconductor film having more excellent superconductivity can be obtained. As a result, an oxide superconductor microstructure having better superconducting properties can be obtained.

In the method for forming an oxide superconductor microstructure according to one aspect or another aspect, the oxide superconductor film is a Bi—Sr—Ca—Cu—O-based oxide superconductor film, and the molecular beam is Bi may be contained (claim 13).

Here, the crystal orientation of the oxide superconductor film is
The inventors have confirmed by experiments that the molecular beam containing Bi has a strong dependence on the incident direction to the substrate. Therefore, the crystal orientation of the oxide superconductor film can be reliably controlled by adjusting the incident direction of the Bi molecular beam.

In the method of forming an oxide superconductor microstructure according to one aspect or another aspect, the oxide superconductor film may be a Bi—Sr—Ca—Cu—O-based oxide superconductor film. (Claim 14).

In the method for forming a fine structure of an oxide superconductor according to the above aspect or another aspect, the step of forming the projection or the depression on the substrate may include the step of irradiating the substrate with a focused ion beam. (Claim 15).

Here, in the processing using the focused ion beam, fine processing on the submicron level can be performed with high precision, so that a projection or a depression having a submicron size can be easily formed. As a result, a submicron oxide superconductor microstructure can be easily formed.

Further, since it is not necessary to form a mask pattern on the substrate and the substrate can be processed directly, the manufacturing process can be simplified.

An oxide superconductor microstructure according to another aspect of the present invention includes a substrate and an oxide superconductor film. The substrate has a convex portion or a concave portion. The oxide superconductor film is formed on the top surface of the convex portion or the bottom surface of the concave portion.

For this reason, in the manufacturing process, a convex portion or a concave portion is previously formed on the substrate, and then an oxide superconductor film is formed on the top surface of the convex portion or the bottom surface of the concave portion. An oxide superconductor film having a predetermined shape can be obtained without directly performing etching or the like on the superconductor film. As a result, since the oxide superconductor film is not directly processed by etching, focused ion beam, or the like, it is possible to prevent the oxide superconductor film from being damaged by the processing. For this reason, deterioration of the superconducting characteristics of the oxide superconducting film can be prevented. Thereby, an oxide superconductor fine structure without deterioration of superconductivity can be obtained.

The oxide superconductor microstructure according to another aspect of the present invention includes a substrate and an oxide superconductor film. The substrate has a convex portion or a concave portion. The oxide superconductor film is formed on the side wall of the projection or the recess (claim 17).

For this reason, in the manufacturing process, a convex portion or a concave portion is formed on the substrate in advance, and then the oxide superconducting film is formed on the side wall of the convex portion or the concave portion. An oxide superconductor film having a predetermined shape can be obtained without directly performing etching or the like on the body film. As a result, the oxide superconductor film is not directly processed by etching or a focused ion beam.
It is possible to prevent the oxide superconductor film from being damaged due to these processes. For this reason, deterioration of the superconducting characteristics of the oxide superconducting film can be prevented. Thereby, an oxide superconductor fine structure without deterioration of superconductivity can be obtained.

[0049]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a process flow chart in Embodiment 1 of a method for forming an oxide superconductor fine structure according to the present invention. With reference to FIG. 1, a method for forming an oxide superconductor fine structure will be described.

Referring to FIG. 1, the method for forming an oxide superconductor fine structure includes a step of forming a pattern on a substrate (S
1) and a step (S2) of forming a superconductor thin film made of an oxide superconductor on the pattern. in this way,
Since the superconducting thin film is formed on a pattern formed in advance on the substrate, the superconducting thin film can be formed into a predetermined shape without directly processing such as etching.

FIGS. 2 to 4 are schematic perspective views showing Embodiment 1 of the method for forming an oxide superconductor fine structure according to the present invention. With reference to FIGS. 2 to 4, a method for forming the oxide superconductor fine structure will be specifically described.

As shown in FIG. 2, first, a substrate 1 is prepared. As the substrate 1, a single crystal substrate of (001) strontium titanate (SrTiO ₃ ) is used. The external dimensions of the substrate 1 are 5 mm long × 5 mm wide × 0.5 m thick.
m.

Next, as shown in FIG. 3, a mesa pattern 2 is formed on the surface of the substrate 1 by processing the flat surface of the substrate 1 using a focused ion beam. Here, when the mesa pattern 2 is formed using the focused ion beam, the surface of the substrate 1 can be directly processed without forming a mask pattern or the like on the substrate 1. The beam diameter of the focused ion beam is about 50 nm. Therefore, the mesa pattern 2 can be formed with an accuracy of a resolution of 100 nm or less.

When the mesa pattern 2 is formed, the substrate 1 may be damaged due to the processing using the focused ion beam. The damaged surface of the substrate 1 may be partially amorphous. However, such an amorphous substrate 1 is subjected to a heat treatment of raising the temperature to 740 ° C. in an oxygen atmosphere before forming the oxide superconductor thin film, whereby the amorphous portion is formed. Can be restored to the state before the damage was dealt.

Here, as the conditions for using the focused ion beam, the following conditions were used. The acceleration voltage of the ion beam was 30 kV. The beam diameter is about 50 nm when the ion current is 80 pA. The ion irradiation density is 4.8 × 10 ¹⁸ ions / cm ² .

Thus, the mesa pattern 2 having a length of 0.1 to 1 μm × a width of 0.1 to 1 μm × a height of 0.1 to 1 μm is obtained.
To form

Next, as shown in FIG. 4, a bismuth-based oxide superconductor (Bi ₂ Sr ₂ CaCu) is formed on the surface of the substrate 1 and the mesa pattern 2 by using a molecular beam epitaxy method.
₂ O _X) of the thin film 3a, it forms a 3b. The substrate temperature at this time was 740 ° C. Further, an oxygen gas having an ozone concentration of about 10% was blown to the vicinity of the substrate 1 as an oxidizing agent. The amount of the oxygen gas sprayed is adjusted so that the back pressure of the chamber of the molecular beam epitaxy apparatus becomes 2.5 × 10 ⁻⁵ Ba. Thus, by using the molecular beam epitaxy method, a thin film of an oxide superconductor having excellent orientation and good crystallinity can be formed. Also,
At this time, since the oxide superconductor thin film 3a grows on the mesa pattern 2 in a self-organizing manner, a fine structure surrounded by facets (crystal faces) that are flat at the electronic level can be formed.

As described above, by forming the mesa pattern 2 in advance and forming the oxide superconductor thin film 3a thereon, the oxide superconductor thin film 3a having a predetermined shape can be obtained. Therefore, it is not necessary to directly etch the oxide superconductor thin film 3a. As a result, it is possible to prevent the thin film 3a of the oxide superconductor from being damaged due to the etching step and the like. Thereby, due to the damage, the oxide superconductor thin film 3
It is possible to prevent the superconducting characteristic of a from deteriorating.

Further, even when a submicron-sized structure made of a thin film of a high-temperature superconductor is formed, deterioration of the superconductivity due to an etching process does not occur, so that an oxide superconductor fine structure having good superconductivity is obtained. Obtainable.

Further, by forming the planar shape of the mesa pattern 2 into a square shape or a polygonal shape, a Josephson junction can be easily formed by utilizing the corners of the polygonal shape. In addition, by adjusting the planar shape of the mesa pattern 2, circuit elements such as capacitors and inductors can be easily formed using oxide superconductors.

Further, by adjusting the irradiation direction of the molecular beam in the molecular beam epitaxy, the crystal orientation of the mesa pattern surface on which the thin film 3a of the oxide superconductor is formed and the side surface of the thin film 3a can be controlled. .

Here, the oxide superconductor thin film 3
Although the molecular beam epitaxy method was used to form a and 3b, similar effects can be obtained by using another method of forming a thin film of an oxide superconductor.

FIGS. 5 and 6 are electron micrographs of Embodiment 1 of the oxide superconductor microstructure according to the present invention.

FIG. 7 is a schematic diagram of the electron micrograph shown in FIG. Referring to FIG. 7, the side surface of the mesa pattern 2 is substantially parallel to the [010] direction or the [100] direction of the strontium titanate substrate when represented by the Miller index. Further, a thin film 3a made of an oxide superconductor is formed on the mesa pattern 2. The arrows in the figure indicate Bi, Cu, C in the molecular beam epitaxy method.
The irradiation direction of the molecular beam containing a and Sr is shown.

FIG. 8 is an electron micrograph of the oxide superconductor microstructure in the region shown in FIG.

FIG. 9 is a schematic view of the electron micrograph shown in FIG. Referring to FIG. 9, thin films 3 a and 3 b of bismuth-based oxide superconductor are formed on the top surface and side surfaces of mesa pattern 2.

When the thin film 3a of the oxide superconductor thus obtained was examined by using X-ray diffraction, the c-axis of the thin film 3a was oriented perpendicular to the substrate 1 (see FIG. 4). Confirmed that. In addition, the [110] direction and [1-1]
It was confirmed that the a-axis or b-axis of the thin film 3a was oriented substantially parallel to the [0] direction. According to observation with an electron microscope, the thin films 3a and 3b were found to have (100), (01)
0), (001), (110), and (1-10). Here, the negative value of the Miller index is represented by, for example, “−1”.

In this case, since the direction of incidence of the molecular beam on the substrate is inclined by 35 ° with respect to the vertical direction, the thin film 3c is also formed on the side surface of the mesa pattern 2.

Here, since strontium titanate is used as the substrate 1, the oxide superconductor thin films 3a and 3c having excellent superconductivity can be easily formed. Further, the side surface of the mesa pattern 2 is [100] of the substrate.
Direction, a plane substantially parallel to the [010] direction. It is easy to form an oxide superconductor by epitaxial growth on a plane substantially parallel to the [100] and [010] directions of the substrate, and to form a thin film having good superconducting properties. Can be.

In the molecular beam epitaxy method, the crystal orientation of the oxide superconductor thin films 3a and 3c can be controlled by adjusting the irradiation direction of the molecular beam.
Here, since the oxide superconductor has strong anisotropy, it is necessary to direct the a-axis or the b-axis of the crystal of the oxide superconductor in the direction in which current flows. Also in this case, by adjusting the irradiation direction of the molecular beam in the molecular beam epitaxy method,
The crystal orientation can be controlled so that the a-axis or b-axis of the crystals of the thin films 3a and 3c made of oxide superconductors are oriented in a predetermined direction.

Here, as a result of the SEM analysis and the EDX analysis, the crystal orientation of the thin films 3a and 3c showed a strong dependence on the incident direction of the molecular beam including Bi in particular. Therefore, if the incident direction of the molecular beam containing Bi to the substrate 1 is adjusted, the crystal orientation of the thin films 3a and 3c can be surely controlled.

FIGS. 10 and 11 are schematic perspective views showing a modification of the first embodiment of the method for forming an oxide superconductor fine structure according to the present invention. Referring to FIGS. 10 and 11,
A modification of the method for forming an oxide superconductor fine structure according to the first embodiment of the present invention will be described.

First, a strontium titanate substrate 1 is prepared in the same manner as in the step shown in FIG. And FIG.
As shown in (1), an opening 4 is formed in the surface of the substrate 1 using a focused ion beam. Here, the planar shape of the opening 4 is 0.1 to 1 μm square, and the depth of the opening 4 is 0.1 μm.
The thickness was 1 to 1 μm. The processing conditions are the same as the processing conditions using a focused ion beam used in the method for forming an oxide superconductor microstructure shown in FIGS.

Next, as shown in FIG. 11, the oxide superconductor thin films 3b and 3d were formed on the substrate 1 by using the same steps as those shown in FIG. As a result, the same effect as in the first embodiment of the present invention can be obtained.

(Embodiment 2) FIGS. 12 and 13 are schematic perspective views showing Embodiment 2 of a method for forming an oxide superconductor fine structure according to the present invention. A method for forming an oxide superconductor microstructure will be described with reference to FIGS.

First, as in the process shown in FIG.
Prepare Next, as shown in FIG. 12, a line pattern 5 is formed on the substrate 1 using a focused ion beam.
The line pattern 5 has a line width of 0.1 to 1 μm, a height of 0.1 to 1 μm, and a length of 0.1 to 1 μm. The processing conditions using the focused ion beam at this time were the same as the processing conditions using the focused ion beam in the first embodiment of the present invention.

Next, as shown in FIG. 13, the oxide superconductor thin films 3b, 3e are formed on the substrate 1 and the line pattern 5.
To form For forming the oxide superconductor thin films 3b and 3e, a molecular beam epitaxy method is used as in the first embodiment of the present invention. The process conditions of this molecular beam epitaxy method were basically the same as those of the first embodiment of the present invention.
A bismuth-based oxide superconductor was formed as the oxide superconductor.

Here, the formed oxide superconductor thin film 3
e was investigated by X-ray diffraction. As a result, the c-axis of the oxide superconductor thin film 3 e was oriented almost perpendicular to the surface of the substrate 1. In addition, the [110] direction and [1-10] direction of the substrate 1 were obtained by reflection high energy electron diffraction.
It was confirmed that the a-axis or the b-axis of the crystal of the thin film 3e was oriented substantially parallel to the direction. Further, by observing the thin film 3e formed on the line pattern 5 with an electron microscope, the thin film 3e of the oxide superconductor becomes
(100), (010), (001), (110),
It was confirmed that it had a structure surrounded by the crystal plane of (1-10).

Here, the thin film 3e is formed on the line pattern 5 to form a linear pattern. Then, the linear thin film 3 made of this oxide superconductor
Since e has not been subjected to processing such as etching, e is not damaged. Therefore, it is possible to prevent the problem that the superconductivity of the thin film 3e is deteriorated due to the damage.

Further, since the linear thin film 3e can be formed without deteriorating the superconducting characteristics, elements and wiring using the oxide superconductor can be easily formed. . Further, even if a wiring having a submicron level line width smaller than the conventional processing limit is formed, the superconducting characteristics are not deteriorated. Therefore, miniaturization and high integration of an element using an oxide superconductor are performed. It becomes easier.

FIGS. 14 and 15 are schematic perspective views showing a modification of the second embodiment of the method for forming an oxide superconductor fine structure according to the present invention. Referring to FIGS. 14 and 15,
A modification of the method for forming the oxide superconductor microstructure will be described.

First, as in the process shown in FIG.
Prepare Next, as shown in FIG. 14, a groove 6 is formed on the surface of the substrate 1 using a focused ion beam. The width of the groove 6 is about 0.1 to 1 μm, and the depth is about 0.1 to 1 μm. The processing conditions using the focused ion beam were basically the same as the processing conditions using the focused ion beam used in the process shown in FIG.

Next, as shown in FIG. 15, the oxide superconductor thin films 3b and 3f are formed on the surface of the substrate 1 by using the molecular beam epitaxy method. The conditions of the molecular beam epitaxy method are basically the same as the conditions of the molecular beam epitaxy method in the step shown in FIG. As a result, a linear oxide superconductor thin film 3f can be formed on the bottom surface of the groove 6. As a result, the same effects as those of the method for forming an oxide superconductor fine structure according to the second embodiment of the present invention shown in FIGS. 12 and 13 can be obtained.

FIGS. 16 and 17 are electron micrographs of the oxide superconductor microstructure according to the second embodiment of the present invention.

Referring to FIG. 16, there is shown a thin line formed of an oxide superconductor extending obliquely from upper right to lower left. The fine line is formed so as to extend substantially parallel to the [110] direction of the substrate. Referring to FIG. 17, a thin line made of an oxide superconductor is shown extending in the horizontal direction. This thin line corresponds to [10] on the substrate.
0] direction.

(Embodiment 3) FIGS. 18 and 19 are a scanning ion micrograph and an electron micrograph showing Embodiment 3 of the method for forming an oxide superconductor microstructure according to the present invention.

As shown in FIG. 18, a mesa pattern of three sizes was formed on a strontium titanate single crystal substrate using a focused ion beam. The size of the mesa pattern is 2 μm × 2 μm, 1 μm × 1 μm
m, length 0.5 μm × width 0.5 μm.

Next, as shown in FIG. 19, a thin film made of an oxide superconductor was formed on the mesa pattern.

The method of forming the mesa pattern and the thin film is basically the same as that of the first embodiment of the present invention.

FIG. 20 is a schematic diagram of the electron micrograph shown in FIG. Here, the arrow in the figure indicates the irradiation direction of the molecular beam containing Bi, Cu, Ca, and Sr in the molecular beam epitaxy method.

FIGS. 21 and 22 show the results of X-ray analysis performed on the region shown in FIG.

FIG. 21 is a graph showing T in the area shown in FIG.
It is a figure showing the measurement result of i concentration distribution.

FIG. 22 is a view showing the state of B in the area shown in FIG.
It is a figure showing the measurement result of i concentration distribution.

It should be noted that the embodiment disclosed this time is an example in all respects and is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0096]

As described above, according to the first to seventeenth aspects of the present invention, a convex portion or a concave portion is previously formed on the substrate, and the oxide superconductor is formed on the top surface of the convex portion or the bottom surface of the concave portion. Since a film is formed, an oxide superconductor film having a required shape can be obtained by adjusting the shape of the top surface of the convex portion or the bottom surface of the concave portion. Further, at this time, the oxide superconductor film is not directly subjected to processing such as etching, so that it is not damaged. As a result, it is possible to prevent the superconducting properties of the oxide superconductor film from deteriorating due to these damages. As a result, it has become possible to form a submicron-sized oxide superconductor fine structure without deteriorating the superconducting characteristics.

[Brief description of the drawings]

FIG. 1 is a process flow chart in Embodiment 1 of a method for forming an oxide superconductor microstructure according to the present invention.

FIG. 2 is a schematic perspective view showing a first step of Embodiment 1 of the method for forming an oxide superconductor fine structure according to the present invention.

FIG. 3 is a schematic perspective view showing a second step of Embodiment 1 of the method for forming an oxide superconductor fine structure according to the present invention.

FIG. 4 is a schematic perspective view showing a third step of the first embodiment of the method for forming an oxide superconductor fine structure according to the present invention.

FIG. 5 is an electron micrograph of Embodiment 1 of the oxide superconductor microstructure according to the present invention.

FIG. 6 is an electron micrograph of Embodiment 1 of the oxide superconductor microstructure according to the present invention.

FIG. 7 is a schematic view of the electron micrograph shown in FIG.

8 is an electron micrograph of the oxide superconductor microstructure in the region shown in FIG. 6, which is obliquely observed.

FIG. 9 is a schematic diagram of the electron micrograph shown in FIG.

FIG. 10 is a schematic perspective view showing a first step of a modification of the first embodiment of the method for forming an oxide superconductor fine structure according to the present invention.

FIG. 11 is a schematic perspective view showing a second step of the modified example of the first embodiment of the method for forming an oxide superconductor fine structure according to the present invention.

FIG. 12 is a schematic perspective view showing a first step of Embodiment 2 of the method for forming an oxide superconductor fine structure according to the present invention.

FIG. 13 is a schematic perspective view showing a second step of Embodiment 2 of the method for forming an oxide superconductor fine structure according to the present invention.

FIG. 14 is a schematic perspective view showing a first step of a modification of the second embodiment of the method for forming an oxide superconductor fine structure according to the present invention.

FIG. 15 is a schematic perspective view showing a second step of the modified example of the second embodiment of the method for forming an oxide superconductor fine structure according to the present invention.

FIG. 16 is an electron micrograph of Embodiment 2 of the oxide superconductor microstructure according to the present invention.

FIG. 17 is an electron micrograph of Embodiment 2 of the oxide superconductor microstructure according to the present invention.

FIG. 18 is a scanning ion micrograph showing a first step of Embodiment 3 of the method for forming an oxide superconductor fine structure according to the present invention.

FIG. 19 is an electron micrograph showing a second step in Embodiment 3 of the method for forming an oxide superconductor fine structure according to the present invention.

20 is a schematic view of the electron micrograph shown in FIG.

21 is a diagram showing a measurement result of the Ti concentration distribution in the region shown in FIG. 19 by X-ray analysis.

22 is a diagram showing a measurement result of the Bi concentration distribution in the region shown in FIG. 19 by X-ray analysis.

FIG. 23 is a schematic cross-sectional view showing a conventional oxide superconductor microstructure.

24 is a schematic cross-sectional view showing a first step of the method for forming the conventional oxide superconductor microstructure shown in FIG.

FIG. 25 is a schematic cross-sectional view showing a second step of the method for forming the conventional oxide superconductor fine structure shown in FIG. 23.

FIG. 26 is a schematic sectional view showing a third step of the method for forming the conventional oxide superconductor fine structure shown in FIG. 23.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Mesa pattern 3, 3a-3f Thin film of oxide superconductor 4 Opening 5 Line pattern 6 Groove

Continued on the front page (72) Inventor Sedai Kawahara 2-24-16 Nakamachi, Koganei-shi, Tokyo Tokyo University of Agriculture and Technology Department of Physical Systems Engineering (72) Inventor Hisato Kaneko 2-24-16, Nakamachi, Koganei-shi, Tokyo (72) Inventor Katsuaki Sato 1087-169 Kami Aso, Aso-ku, Kawasaki City, Kanagawa Prefecture F term (reference) 4G047 JA03 JB02 JC10 KE07 KG01 KG03 KG07 5G321 AA05 BA07 CA04 CA21 CA27 CA28 DB36

Claims (17)

[Claims] An oxide superconductor microstructure comprising: a step of forming a projection or a depression on a substrate; and a step of forming an oxide superconductor film on a top surface of the projection or a bottom surface of the depression. Formation method. 2. A method for forming a fine oxide superconductor structure, comprising: forming a convex portion or a concave portion on a substrate; and forming an oxide superconductor film on a side wall of the convex portion or the concave portion. . 3. The method for forming an oxide superconductor fine structure according to claim 1, wherein a height from a surface of the substrate to a top surface of the projection is 1.0 μm or less. 4. The method according to claim 1, wherein a depth from a surface of the substrate to a bottom surface of the concave portion is 1.0 μm or less. 5. The method for forming an oxide superconductor fine structure according to claim 1, wherein the top surface or the bottom surface has a polygonal planar shape. 6. The method for forming an oxide superconductor fine structure according to claim 5, wherein one side of the polygon has a length of 1.0 μm or less. 7. The method for forming an oxide superconductor microstructure according to claim 1, wherein a planar shape of the top surface or the bottom surface is linear. 8. The method according to claim 7, wherein the width of the line is 1.0 μm or less. 9. The method for forming an oxide superconductor microstructure according to claim 1, wherein the substrate contains strontium titanate. 10. The side wall of the ridge or the valley of the strontium titanate represented by Miller index [1].
The method for forming an oxide superconductor microstructure according to claim 9, which has a plane substantially parallel to the [00] direction or the [110] direction. 11. The method according to claim 1, wherein the step of forming the oxide superconductor film includes a step of forming the oxide superconductor film using a molecular beam epitaxy method.
13. The method for forming an oxide superconductor microstructure according to item 8. 12. The step of forming the oxide superconductor film by using the molecular beam epitaxy method includes a step of adjusting an incident direction of a molecular beam irradiated on the substrate with respect to the substrate surface. 12. The method for forming an oxide superconductor microstructure according to item 11. 13. The oxide superconductor film according to claim 1, wherein the Bi-Sr-
The method for forming an oxide superconductor microstructure according to claim 12, wherein the method is a Ca-Cu-O-based oxide superconductor film, wherein the molecular beam contains Bi. 14. The oxide superconductor film is formed of Bi-Sr-
A Ca-Cu-O-based oxide superconductor film,
13. The method for forming an oxide superconductor microstructure according to any one of 12 above. 15. The oxide superconductor microstructure according to claim 1, wherein the step of forming the projection or the depression on the substrate includes a step of irradiating the substrate with a focused ion beam. Formation method. 16. An oxide superconductor microstructure comprising: a substrate having a projection or a depression formed thereon; and an oxide superconductor film formed on a top surface of the projection or a bottom surface of the depression. 17. An oxide superconductor microstructure comprising: a substrate on which a projection or a recess is formed; and an oxide superconductor film formed on a sidewall of the projection or the recess.