JPH04134877A - Superconducting element and manufacture thereof - Google Patents

Abstract

PURPOSE:To eliminate an ultrafine processing of a special region by composing a superconducting element of a superconductor of a desired thickness formed by inputting oxygen. CONSTITUTION:A resist layer 4 is removed with its middle part left unremoved, and, oxygen ions are deeply implanted from above a compound thin film 2. An oxygen ion implanted region 3 to be formed in this case is formed substantially entirely in thickness of the film 2. On the other hand, an oxygen ion implanted region is not formed at the center masked by the resist layer. Then, after the resist layer is removed, it is annealed in an oxygen atmosphere to increase the oxygen ion implanted region 3, and oxygen in the atmosphere is introduced to the region masked by the resist layer in the previous step. In this case, since oxygen is easily diffused in a horizontal direction in the film 2, the diffused region couples both the oxygen ion implanted region 3 to be weakly connected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a superconducting element and a method for manufacturing the same. More specifically, the present invention relates to a superconducting element including a weak bond formed by an oxide superconducting thin film whose effective film thickness varies, and in particular, a superconducting element having a novel configuration in which the surface thereof is flat; The present invention relates to a novel manufacturing method for realizing this.

BACKGROUND OF THE INVENTION Since conventionally known superconducting materials generally become superconductors only at extremely low temperatures below the temperature of liquid helium, little thought has been given to their practical use. However, [La.

[3a:] 2cu○4 or [:La, Sr]
Since it was discovered in 1986 that composite oxide sintered bodies such as 2cu○2 are superconducting materials with high critical temperatures, Y-BaCu-based or Bi-Ca-3r-C
It has been confirmed one after another that U-based and other complex oxides exhibit superconducting properties in extremely high temperature ranges. Materials that exhibit superconducting properties at such high temperatures can be used with inexpensive liquid nitrogen as a cooling medium, so the application of superconducting technology suddenly began to be considered as a realistic issue.

Josephson devices are known as one of the basic electronic devices that utilize superconductivity.

A Josephson device is formed by a pair of superconducting electrodes connected by so-called weak coupling, and exhibits the DC Josephson effect, which is said to be the tunneling effect of a pair of Coopers, and discrete voltage/current characteristics. It has unique characteristics such as the AC Josephson effect.

On the other hand, a series of oxide superconducting materials were initially obtained as sintered bodies by powder metallurgy, but the sintered materials did not have favorable properties, particularly in terms of critical current density.
Recently, methods for producing thin films have been widely studied. The structure of a planar Josephson element manufactured by processing such an oxide superconducting thin film can be roughly divided into a constant film thickness type and a variable thickness type.

FIGS. 3(a) and 3(a) are diagrams showing a typical structure of a planar Josephson element.

FIG. 3(a) is a diagram showing the structure of a constant-thickness type Josephson device, and as shown in the figure, an oxide superconducting thin film 21 with a constant thickness formed on a substrate 11 is patterned. By doing so, a pair of superconducting electrode regions 11a and 21c having a sufficient line width and a weak coupling region 21a having a very narrow line width W are formed.

On the other hand, FIG. 3 (Corporation) is a diagram showing the structure of a Josephson element of variable thickness type, in which by thinning a specific region of the oxide superconducting thin film 21 formed on the substrate Il,
A pair of superconducting electrode regions 21b, 21 having sufficient thickness
c, and a very thin weak coupling region 21a having a film thickness t.

In various planar Josephson elements having the above configurations, the film width W or the film thickness t of the weak coupling region 21a is
are closely related to the characteristics of the device, and high processing accuracy on the submicron level is required to achieve the desired characteristics with good reproducibility.

Problems to be Solved by the Invention The conventional planar Josephson element as described above has
Each has the following problems.

That is, the fixed-thickness type Josephson device has a relatively flat surface and has a preferable structure as an integrated circuit device. However, in order to form the weak coupling region 21a, it is necessary to pattern the oxide superconducting thin film 21 having a thickness of about 0.5 to 1.0 μm to a width of 0.2 μm or less. It is actually very difficult to carry out such ultra-fine processing with good reproducibility.

On the other hand, the thickness-variable Josephson element has a weak coupling region 2
Although extreme microfabrication technology is not required for patterning 1a itself, it is extremely difficult to uniformly control the residual film thickness t of the weakly coupled region 21a. Furthermore, the flatness of the element surface is poor, which is disadvantageous when used as an element constituting an integrated circuit.

Therefore, the present invention solves the above-mentioned problems of the conventional technology, and provides a new Josephson element configuration that can be manufactured with good reproducibility using already established processing techniques and that allows easy flattening of the element surface. The purpose is to provide a novel manufacturing method for realizing this configuration.

Means for solving the problem, that is, according to the present invention, a pair of superconducting electrode regions formed by a sufficiently thick oxide superconducting thin film and a thin superconducting thin film weakly coupling the pair of superconducting electrode regions. A compound formed on a substrate using a compound that can be made into an oxide superconductor by implanting oxygen ions into an oxide superconductor by bonding a weak coupling region with a superconducting element mounted on the same surface of the substrate. a thin film; a pair of superconducting electrode regions formed by implanting oxygen ions into the compound thin film;
A superconducting element is provided, comprising a weak coupling region formed to weakly couple the pair of superconducting electrode regions to each other by introducing oxygen into the compound thin film.

Further, as a method for producing the superconducting element according to the present invention, according to the present invention, a thin film is formed on the film-forming surface of the substrate using a compound that can be made into an oxide superconductor by implanting oxygen ions. a step of implanting oxygen ions into the superconducting electrode region of the thin film;
A method for manufacturing a superconducting element is provided, the method comprising the step of introducing oxygen into the weak bonding region.

Function The superconducting element according to the present invention includes a superconducting electrode formed of an oxide superconductor formed by implanting oxygen ions,
Its main feature is that it also has a weak bond formed by an oxide superconductor formed by introducing oxygen.

That is, in conventional superconducting elements, weak bonds are formed by physically processing a previously formed superconducting thin film to thin or thin the weak bond region. However, the film width or film thickness that can achieve weak coupling is extremely small.
Extremely high processing precision was required to fabricate Josephson elements that exhibited desired characteristics.

On the other hand, in the superconducting element according to the present invention, after forming a thin film of a compound in which oxygen is removed or deficient in oxygen from an oxide superconductor on a substrate, oxygen is applied to the thin film of the compound under appropriate conditions. Superconducting electrodes are formed by implanting ions. Further, by utilizing the fact that oxygen easily moves in the horizontal direction when heated in an oxygen atmosphere, weakly bonded regions are bonded by introducing oxygen. Therefore, fine physical processing is not necessary, and the controllability and reproducibility of characteristics are excellent. Furthermore, since the surface of this superconducting element is already flat upon completion, it is suitable for use as an integrated circuit element.

Materials for forming the oxide superconducting thin film in the superconducting element according to the present invention as described above include Yea-cu-o system, Bi-5r-Ca-Cu-0 system, Tl-Ba
-Ca-Cu-0-based composite oxide superconducting materials can be exemplified.

In addition, preferred base substrate materials for forming the above-mentioned oxide superconducting material thin film include MgO1SrTIOh, Cd
An example is an oxide single crystal substrate such as NdAlO4. It is possible to grow highly oriented crystals on these substrates. Further, a semiconductor substrate such as an 81 substrate mounted with a suitable buffer layer can also be used as the base substrate.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention in any way.

Embodiment FIG. 1 is a diagram showing a specific example of the configuration of a superconducting element according to the present invention.

As shown in the figure, this element mainly consists of a substrate 10 and a compound thin film 20 formed on the substrate 10, and a specific region in the compound thin film 20 is an oxygen introduction region 30. It has become. That is, the oxygen introduction region 30 forms an implanted region into which oxygen ions are implanted in the superconducting electrode regions 30b and 30c, and in the weak coupling electrode region 30a,
Oxygen is introduced to form a thin superconducting region.

Here, the compound thin film 20 in this element is formed of a compound that is not a superconductor per se, but becomes an oxide superconductor by implanting oxygen ions. Therefore, the oxygen-introduced region 30 formed by introducing an appropriate amount of oxygen into the compound thin film 20 becomes a superconductor. Note that as such a compound, an oxide superconducting material whose oxygen content is intentionally made insufficient may be used.

FIGS. 2(a) to 2(f) are diagrams showing each step of the manufacturing process of a superconducting element according to the present invention. In this example, a Y-Ba-Cu based composite oxide superconducting material is used as the oxide superconducting material.

A flat substrate l as shown in FIG. 2(a) is prepared.

In this embodiment, an Alga (100) substrate is used as the substrate 1, but it is also possible to preferably use a CdNdA]04 (001) substrate or the like. By using such a substrate, a C-axis oriented oxide superconducting thin film having a large critical current density in a direction parallel to the surface of the substrate 1 can be grown on the substrate.

A compound thin film 2 is formed on the substrate 1 as described above, as shown in FIGS. The compound thin film 2 formed here is a Y-8a-Cu composite oxide, but the oxygen content is intentionally made insufficient, and the compound film 2 itself does not become a superconductor even when cooled.

Incidentally, such a compound thin film 2 can be formed by, for example, an oxidative sputtering method or a reactive vapor deposition method. In this example, the film was formed by the off-axis sputtering method in an Ar-based gas atmosphere of 10 Pa. The substrate temperature was 700°C.

Next, as shown in FIG. 2(C), on the compound thin film 2,
A resist layer 4 is formed in a predetermined pattern.

This resist layer 4 is used for the purpose of suppressing the amount of oxygen ions implanted into the weakly bonded region in the oxygen ion implantation process described later.

Subsequently, as shown in FIG. 2(d), slight grooves 2a are formed in the surface of the compound thin film 2 by anisotropic etching such as reactive ion etching or ion milling using argon gas. Incidentally, here, grooves 2a are formed in the compound thin film 2.
The purpose of forming the weak coupling portion is to sharpen the shape of the weak coupling portion, as will be described later. Therefore, if shallow steps can be formed by etching with good controllability, etching may be performed uniformly leaving only the weak bond portions.

After the above pre-process, as shown in FIG. 2(e), after removing the resist layer 4 leaving the central resist layer 4a, oxygen ions are implanted deeply from above the compound thin film 2. As shown in the figure, the oxygen ion implantation region 3 formed at this time has two sides on both sides which will later become superconducting electrode regions.
It is formed over substantially the entire thickness of the compound thin film 2. On the other hand, no oxygen ion implantation region is formed in the central portion masked by the resist layer 4a.

Next, as shown in FIG. 2(f), by annealing in an oxygen atmosphere after removing the resist layer 4a, the oxygen ion implantation region 3 is enlarged, and the resist layer 4a is masked in the previous step. Oxygen in the atmosphere is introduced into the area that was previously exposed. At this time, within the compound thin film 2, oxygen tends to diffuse horizontally, so the oxygen taken in from the side surfaces of the grooves 2a formed by etching in the previous process diffuses horizontally, and eventually this diffusion region becomes The ion implanted regions 3 are bonded together to form a weak bond.

Through such processing, as shown in the figure, a pair of superconducting electrode regions 3b and 3C into which oxygen ions are deeply implanted,
Oxygen is introduced and horizontally diffused weak bonding regions 3a are formed. Note that this heat treatment was performed at 400° C., and the effective thickness of the superconducting layer in the weak coupling region 3a of the superconducting element finally obtained was about 5 to 1 Onm.

In the manner described above, a superconducting element according to the present invention as shown in FIG. 1 is completed.

As described in detail, the superconducting element according to the present invention does not physically process a portion of a superconducting thin film to form a weak bond, but rather forms a superconducting layer of a desired thickness by incorporating oxygen. It is made up of the body. Therefore, its fabrication does not require ultra-fine processing for specific areas, and at the same time
It requires less man-hours and is highly productive.

Moreover, the superconducting element according to the present invention is easy to handle as an integrated circuit element because the surface of the element is already flattened at the time of manufacture due to its unique configuration.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a specific configuration example of a superconducting element according to the present invention, and FIGS. 2 (a) to (f) are diagrams showing each step of the manufacturing process of a superconducting element according to the present invention. FIGS. 3(a) and 3(b) are diagrams showing a typical configuration of a conventional Brehner type Josephson element. [Main reference numbers] 1.10.11...Substrate, 2.20...Compound thin film (non-superconductor), 2a...
Groove, 3... Oxygen ion implantation region (superconductor), 4... Resist layer, 21... Oxide superconducting thin film, 3a, 21a, 30a... Weak bonding region, 3 b, 3
c, 21b, 21'c. 30...Oxygen introduction region (superconductor), 30b, 30C
...Superconducting electrode area patent applicant Sumitomo Electric Industries, Ltd.

Claims (2)

[Claims] (1) 1 formed from a sufficiently thick oxide superconducting thin film
A superconducting element is formed by mounting a pair of superconducting electrode regions and a weak coupling region formed by a thin superconducting thin film that weakly couples the pair of superconducting electrode regions on the same surface of a substrate, and oxygen ions are implanted into the superconducting element. a compound thin film formed on the substrate using a compound that can be made into an oxide superconductor by A superconducting element comprising: a weak coupling region formed to weakly couple the pair of superconducting electrode regions to each other by introducing oxygen into a thin film. (2) A method for producing a superconducting element according to claim 1, wherein a thin film is formed on the film-forming surface of the substrate using a compound that can be made into an oxide superconductor by implanting oxygen ions. A method for manufacturing a superconducting element, comprising the steps of: injecting oxygen ions into the superconducting electrode region of the thin film; and introducing oxygen into the weak bonding region.