JPH0634413B2 - Superconducting device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fixed electron device using an oxide-based superconducting (also referred to as superconducting but also referred to as superconducting here) material.

The present invention relates to a horizontal junction type Josephson device having an input terminal and an output terminal or a control electrode used in such a structure.
A terminal (including three terminals) device.

“Prior art” Conventionally, superconducting materials such as Nb-Ge (for example, Nb ₃ G
Attempts have been made to make solid-state electronic devices using metallic materials such as e).

The representative is the Josephson device shown in FIG. This Josephson device combines the superconducting phenomenon and the tunnel current phenomenon to perform switching.
It consists of a terminal circuit.

In this Josephson junction type device, as shown in FIG. 1, an insulating film (23) is formed on the upper surface of the first superconducting material (21) with a thickness that allows a tunnel current to flow, and further on top of that an insulating film (23) is formed. The superconducting material 2 of (2) was laminated. And it relates to a vertical junction type in which a tunnel current flows vertically.

More recently is also an attempt to implement a superconducting material of one or both of such vertical junction Josephson device of an oxide superconducting material such as _{YBa 2 Cu 3 O 6 ~ 8} .

"Conventional problems" However, when a Josephson device is constructed using an insulating film that is in close contact with the surface of the substrate, as long as an oxide superconducting material is used on or near the surface of the substrate, the amount of oxygen that is originally supposed to be Tended to be scarce compared to. In some cases, even the superconducting property is lost on or near this surface. The present invention has been made to eliminate such drawbacks.

Further, the present invention resides in eliminating the drawback of oxidation concentration sensitivity at or near such surfaces.

The present invention eliminates such drawbacks and provides a Josephson device having a lateral joint structure in which the upper surface is not used for the joint portion. In addition, 4 terminals for ultra high frequency operation
(3 terminals) A circuit device, that is, a control electrode for applying an input signal and an electrode for deriving an output signal are provided.

[Means for Solving the Problem] In order to solve the problem, the present invention provides an oxide superconducting material on the upper surface of the oxide superconducting material or an additive capable of imparting non-superconducting properties to the upper portion of this material by heat treatment. It is added or covered with the same main component material as the oxide superconducting material. The present invention further uses a substrate having a non-superconducting surface in which the same additive is added to the above-mentioned oxide superconducting material or a substrate in which the above-mentioned non-superconducting material is formed on a heterogeneous substrate. A superconducting material having a single crystal or polycrystalline structure in which an ab plane (a plane perpendicular to the c-axis is referred to as a c plane or an ab plane) is oriented parallel to the upper surface of the substrate is used. Furthermore, isolation was performed by adding an additive which continues to lose superconducting properties when heat-treated also in the non-active regions around the periphery of the oxide superconducting material except the active region. This oxide superconducting material has a modified perovskite structure, ab
The current can flow 100 times more in the direction parallel to the plane than in the c-axis direction. Therefore, making this direction parallel to the upper surface of the substrate can produce a large current density, which is effective for a fine process and high integration. By doing so, it is possible to further prevent oxygen from leaking upward at or near the upper surface of the modified perovskite structure in this structure. In addition, as described above, a protective film in which an additive that loses superconducting properties is added to the same material as the oxide superconducting material is provided on the upper surface or the upper portion of the oxide superconducting material, and at the interface with the protective film or in the vicinity thereof. High reliability can be obtained in all regions where superconducting properties should be provided by making the oxygen concentration of the same as or larger than that of the inside (bulk) of the oxide superconducting material.

The peripheral portion of the thus-oriented superconducting material thin film is heat-treated to form an inactive region containing an additive having non-superconducting properties by an ion implantation method of the additive, thereby forming the device, the electrode and the lead. The active region to be formed can be selectively provided without performing any photoetching on the unnecessary portion. If necessary, similar additives may be added to a part of the active region such as the Josephson junction surface (the central region or a region necessary for design).

The order of forming this step and forming the protective film on the upper surface may be reversed.

The present invention is a method for producing a non-superconducting oxide material having finite resistance, in which an additive is added to a predetermined position in a zero resistance oxide superconducting material by an ion implantation method or the like, and heat treatment is further performed. It is an oxide material having a finite resistance.

That is, iron (Fe), nickel (Ni), cobalt (Co), as additives added to the oxide superconducting material having superconducting properties,
Silicon (Si), Germanium (Ge), Boron (B), Aluminum (A
l), gallium (Ga), phosphorus (P), titanium (Ti), tantalum (Ta),
There are one or more types selected from magnesium (Mg). In such a case, the concentration of the additive was 1 to 25 atomic%.

Of these, in particular, Mg and Al have the same price as the oxide superconducting materials with valences II and III of the periodic table, and are easily bonded to oxygen by heat treatment to form an insulating material. for that reason,
1 to 10 atomic% of the oxide superconducting material, preferably 5
Addition at up to 10 atom% can destroy the superconducting properties of heat treatment. And it has almost the same thermal expansion coefficient as this oxide material, and it is possible to prevent the occurrence of cracks due to temperature changes.

Further, elements constituting the oxide superconducting materials represented by IIIaIIa ₂ Cu ₃ O ₆ to ₈ , for example, IIIa group elements Y (yttrium), copper (Cu), IIa group elements barium (Ba), calcium
It may be an oxide non-superconducting material having the same main component as the oxide superconducting material containing (Ca) more than necessary. In such a case, it is necessary to add a large amount such that the stoichiometric ratio exhibiting superconductivity is disturbed. Specifically, 5 x 10 ^{20 to} 2.5 x
It is on the order of 10 ²² cm ^-3 .

However, oxygen constituting a part of the oxide superconducting material is an unsuitable element because it is easily degassed outside in the implanted region in the subsequent thermal annealing.

An example of the superconducting device of the present invention is shown in FIG.

In Fig. 2 (A), a substrate (1) having a non-superconducting material and a superconducting material (1 ') having the same main component on an insulating substrate (1 ") was used. A thin film of oxide conductive material (3
0) was formed on the entire surface. The oxide superconducting materials (3) and (9) are left in order to isolate the peripheral portion of the same as an inactive region to make it an inactive region.
At ~ 2000 KeV, ionize and implant additives such as Al, Mg. By this ion implantation method, the superconducting material is added across (both above and below and in the anterior-posterior direction of the drawing) to form the inactive region (20). At the same time, the thickness of the first oxide material (4) for the device in the active region (2) (see Fig. 2 (A))
(4) Left and right direction) as thin as possible, preferably 1000
It was set to Å or less, and it was made to have the Josephson junction effect.

This area (4) is 1/2 to 1/10 times the density (0.1
-20 atom%). For the peripheral part (20), Al, Mg 5 to 5
Added to a concentration of 10 atom%.

Further, an oxide superconducting thin film (40) is formed on the entire surface by a similar method, and these active regions are covered with a non-active region (11), and a connecting portion (8 ') P (9') for electrodes is formed. Only as the active region, the superconducting property is selectively retained. Then, in exactly the same way, a third layer of oxide superconducting thin film (5
0) is formed. Then, except for the regions of the leads (8) and (9), the same additives as described above are added to the unnecessary thin film in the other regions (21) for insulation. Then, the pair of electrodes / leads (8), (9) for output is formed into a multi-layer wiring, and all active regions of the device, the electrodes, the electrode connecting portions, and the leads are formed of an oxide superconducting material. Further, the non-active region in the peripheral portion can be insulated by adding an additive capable of imparting non-superconducting properties thereto by heat treatment. This electrode (9),
Since both (9 ′) and (5) are oxide superconducting materials and their orientations are such that the ab plane is made parallel to the substrate, there is no problem.

Thus, the Josephson device (2) was constructed and the characteristics shown in FIG. 3 were obtained.

The present invention further provides, in addition to such a two-terminal device, a sufficiently large electrical resistance, preferably an electrical resistance of the first superconducting material, between electrodes connected between a pair of output oxide superconducting materials. Also, a coating having an electric resistance of 10 times or more may be provided on the upper surface, the lower surface or both surfaces, and the control electrode may be provided in close contact with the coating.

Two such examples are shown in FIGS. 2 (B) and (C).

In FIG. 2 (B), the control electrode (10) is provided above the first oxide superconducting material (30), and this electrode is connected to the multilayer wiring connecting portion.
Both (8 '), (9') and electrodes / leads (8), (9), (10) are made of oxide superconducting material.

In Fig. 2 (C), the control electrode (1
0) and (10 ') are provided on both upper and lower sides of the area (4).

Interlayer insulators (11) and (11 ″) also have an additive like the isolation region.
-30 atom%, typically 5-10 atom%, and the same thermal expansion coefficient material or this material may be used as a main component.

2 (B) and (C) of the present invention, a film, preferably an insulating film, having an electric resistance sufficiently larger than that of the oxide superconducting material between the control electrode and the superconducting film. (1
1) was provided by adding the above-mentioned additive only to the upper portion of the oxide superconducting material (30) thereunder. Then, a voltage is applied from the control electrode (10) made of an oxide superconducting material which is an input terminal, and a voltage is applied to the first oxide material (4) below the control electrode.

This material is in an intermediate state between a state of having superconductivity and a state of not having superconductivity at all (partly having superconductivity,
Part of it is in a non-superconducting state, that is, in the temperature range between Tc onset and Tco) and has semiconductor or insulator properties, so its potential depends on the voltage applied to the input control electrode. It can be changed and controlled.

In FIG. 2 of the present invention, the second oxide superconducting material (3), (5)
Is formed over the entire surface, and a large amount of the additive used in the present invention is added to the outer periphery of the desired shape to measure the insulation separation (20) from the adjacent device. Therefore, after adding the additives as described above, or in the case where this step is performed a plurality of times, after each of them or after these steps, the whole of them is heated in oxygen at 400 to 1000 ° C., 0.5 to
50 hours, for example 3 hours at 900 ℃ and 400 while slowly cooling
The temperature was set to 0 ° C., and annealing was further performed at this temperature for 1 hour in oxygen to partially oxidize or replace the impurities with an oxide superconducting material and adjust the crystal structure.

The present invention does not make the oxide superconducting material only on the first layer on the same substrate, but also stacks the oxide superconducting material on the same layer to make the oxide superconducting material on the second layer or further on the third layer. obtain. The active region is selectively formed with respect to these by forming an inactive region by adding an additive. Contrary to the one shown in FIG. 2, the first layer has electrodes and leads.
It is also possible to use a device as the layer. It is also possible in the present invention to arrange the device for each layer. The substrate (1 ″) in FIG. 2 may be a silicon substrate provided with a semiconductor integrated circuit, and the silicon integrated circuit and the superconducting device may be integrated together. The buffer layer (1 ') in the figure is particularly effective.

"Operation" By adopting such a structure, it becomes a lateral junction type, and the superconducting device or its electrode / lead having long-term reliability is used as a protection film for the isolation inactive region under the isolation. It can be left and integrated.

Since the oxide superconducting material has ab planes aligned in parallel with the plane of the substrate, its top surface is also flat and the peripheral part is insulated by adding additives to it. I was able to eliminate the obstacles above.

Thus, a plurality of devices can be made, and when interconnecting such devices based on design logic, when the superconducting integrated circuit is made, its interconnection can be made with zero resistance.

Embodiments will be described below with reference to the drawings.

Example 1 This example shows the structure of FIG. 2 (A).

YSZ (yttrium stabilized zircon) was used as the substrate (1 ″), which was prepared by applying a magnetic field applied plasma coating method, MBE (molecular beam epitaxial) method, CVD (vapor phase reaction) method, An oxide non-superconducting material (1 ′) was formed by using a sputtering method, etc., and was used as a substrate (1). As an example, (A _1-X Bx) yCuzOw, x = 0.1 to 1, y = 2.0 to 4.0, preferably 2.5 to 3.5, z = 1 to 4, preferably 1.5 to 3.5, W =
4-10, preferably 6-8. A is Y (yttrium), Gd (gadrilium), Yb (ytterbium), Eu (europium), Tb (terbium), Dy (dysprosium), Ho (
Holmium), Er (erbium), Tm (thulium), Lu (lutetium), Sc (scandium) or other periodic table
It is selected from one or more kinds of group IIIa.

As B, one or more elements selected from the group IIa of the periodic table of elements Be (barium), Sr (strontium), and Ca (calcium) are used. Particularly, as a specific example thereof, (YBa ₂ ) Cu ₃ O ₆ ~
₈ was used. Further, as A, a lanthanide element or actinide element other than the above-mentioned elements in the periodic table can be used. In addition, the periodic table of elements in this specification is based on a dictionary of physics and chemistry (Iwanami Shoten, published on April 1, 1963).
Simultaneously with or after this formation, thermal annealing was performed at a temperature of 600 to 950 ° C. for 5 to 20 hours, followed by gradual cooling. Thus, the Tco was 91 K as a characteristic of the superconducting material provided with the oxide superconducting material (1) having the same main component on the lower side of the oxide superconducting material (30).

Next, an impurity such as magnesium or aluminum is added to the periphery (20) of the region where the device is to be formed by an ion implantation method to insulate it. Further, impurities are added to the region (4) by reducing it by about 1/5.
That is, in FIG. 2 (A), a photoresist is provided on the regions (3) and (5), and the additive is selectively added to the regions (4) and (20) without the resist by the ion implantation method. I was made to do it. The inactive region (20) was provided by adding an additive of aluminum or magnesium to a concentration of 5 to 10 atomic%, for example, 8 atomic%. After that, the photoresist is removed, and the whole of these is again covered with a thin film of the second layer oxide superconducting material.
(40) was formed. The other parts except the connecting parts (8 ') and (9') were made into the inactive region by the ion implantation method. Thus, a passivation film could be formed above the active region 12 by using the same main component material to which the additive was added. Repeat this again to make the second layer oxide superconducting material (50),
Leads (8), (9) and inactive region (21) were provided by using it. After this, all of them are heated in an oxidizing atmosphere at about 300-950 ° C.
For example, oxidize the entire surface at a temperature of 900 ℃ to fit each film and stack it.
After the temperature reached 0 ° C., oxygen was again added by an ion implantation method as needed to the interface region that had decreased from the stoichiometric ratio by the oxidation step. The heat treatment described above oxidizes the previously added additive and transforms this region into an insulator.

Thus, the characteristics shown in Fig. 3 could be created in the structure shown in Fig. 2 (A).

Example 2 Further, FIG. 2 (B) was manufactured by the same method. In this structure, a silicon substrate is used as the substrate (1 ″), and an integrated circuit has been already formed. A silicon oxide or silicon nitride insulating film is provided on the silicon substrate.
In order to match the coefficient of thermal expansion with this, as shown in FIG. 2 (B), the oxide non-superconducting material (1 ') was provided to a thickness of 2 .mu.m, and the substrate (1) was combined. Further, an active region (2), a non-active region (20) and an upper oxide superconducting material (1 ') were formed on this by the same method as in the first embodiment. Particularly when the leads (8) and (9) were formed, the control electrode (10) was also formed by adding the additive to the peripheral portion at the same time. The output electrode was in close contact with the ceramic thin film so that ohmic contact was made. Examination of the electrical characteristics of such a device revealed that it had the Josephson characteristics shown in FIG. 3 at liquid nitrogen temperature.

The connecting line with the semiconductor integrated circuit (1 ″) was not heat-treated at 400 ℃ or more, and the oxide superconducting material was formed at a temperature up to 400 ℃. This is to prevent the silicon and the silicon constituting the semiconductor from reacting with each other to form silicon oxide at the interface.
Refractory metal (W, Mo, Ti or its silicide) -Non-oxidizing metal
The (Au, Ag) -oxide superconducting material can withstand processing or film formation at 700 ° C for up to 1 hour.

"Effects" In the present invention, a superconducting device, which has been a vertical junction type two-terminal device up to now, is changed to a horizontal junction type two-terminal device or a multi-terminal device and integrated on the same substrate.

Furthermore, because the electrodes and leads are composed of two-layer wiring,
In such a temperature range, the interconnection is made of an oxide superconducting material having a resistance of zero or sufficiently close to zero.

Therefore, it is possible to provide a large number of superconducting devices on the same substrate and integrate them.

In the present invention, 0 or 1 control electrode is shown, but 2 or more control electrodes may be provided in series or in parallel.

At the same time, the periphery of the substrate was selectively separated with an insulator.
You may make a superconducting coil and use it as a SQUID.

In the present invention, the title oxide superconducting material was used. However, this is because the superconducting material is an oxide. It is clear from the technical idea of the present invention that the crystal structure may be polycrystalline or single crystal. Particularly in the case of a single crystal structure, when a superconducting material is used, epitaxial growth may be performed on the substrate.

[Brief description of drawings]

 FIG. 1 shows a vertical sectional view of a conventional superconducting device. FIG. 2 shows a vertical sectional view of the superconducting device of the present invention. FIG. 3 shows the characteristics of the superconducting device made according to the present invention.

Continuation of front page (56) Reference JP-A-58-73172 (JP, A) JP-A-61-206279 (JP, A) JP-A-62-238674 (JP, A) -Jpn. J. Appl. Phys. , vol. 25, no. 7, (JULY 1986), pp. 1132 to 1133 ・ IBM Technical Disclosure Bulletin, vol. 23, no. 4, (Sep. 1980), p. 1683 ・ Appl. Phys. Lett. vol. 51, no. 11, (14 Sep. 1987), pp. 861-863 ・ Appl. Phys. Lett. , Vol. 51, no. 8, (24 Aug. 1987), pp. 619 ~ 621

Claims (3)

[Claims] 1. A superconducting device using an oxide superconducting thin film provided on a substrate, wherein the ab plane of the oxide superconducting thin film is oriented parallel to the upper face of the substrate. A superconducting device, characterized in that a material having the same main component as said oxide superconducting thin film and having non-superconducting properties is provided on the upper surface, lower surface and side periphery of the superconducting thin film. 2. The oxide superconducting thin film according to claim 1, wherein the oxide superconducting thin film is partially doped, and the superconducting property is destroyed in the region where the impurity is added. A superconducting device. 3. The superconducting device according to claim 1, wherein the material having non-superconducting properties is a material forming an oxide superconducting thin film to which impurities are added.