JPH0360175A - Superconductive switching element - Google Patents

Abstract

PURPOSE:To obtain an element whose power consumption is small and whose response speed is high, by forming superconducting thin films so as to sandwich a nonmagnetic metal, forming an electrode thereon, forming further an insulating film, and forming superconducting lead wires for applying magnetic field on the insulating film. CONSTITUTION:The basic constitution of the title element is composed of the following, a substrate 1, a junction part 2 formed of a nonmagnetic metal thin film, superconducting thin films 3 separated by the junction part 2, and superconducting lead wires 4 for applying magnetic field. In addition, electrodes 5 and an insulating film 6 are formed. The superconducting film 3 is formed by using one of superconductors such as Y1Ba2Cu3Ox, Ln1Ba2Cu3Ox whose critical temperatures are higher than 77K. The metal thin film used for the junction part 2 is formed by using one of Nb, Zn, Al, Cu-Al, etc. The nonmagnetic metal thin film 2, the SiO2 thin film 6, and the superconducting lead wires 4 for applying magnetic field are desirable to be manufactured by using vapor-deposition method. The two superconducting lead wires 4 for applying magnetic field are fixed almost above the junction part 2 so as to be parallel with each other. The junction part 2 and the lead wires 4 are manufactured by using photolithography method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a superconducting switch element, and more particularly to an oxide high-temperature superconducting switch element applied to a switch part of an integrated circuit such as a computer.

[Prior art]

Research and development of superconducting materials has been actively conducted everywhere, and most of them are Nb-based superconducting alloys. However, recently, oxide-based superconductors have been attracting attention as new materials that can be applied to the field of electronics. However, the reality is that its application range is largely limited to Josephson elements, 5QUIDs, infrared sensors, etc.

However, photoresponsive switching devices using oxide high-temperature superconductors as switching devices are known (T, Nl5I
NO, H, NAKANE AND U, KASU ABE,
Jpn, J., Appl.

Phys, 26 (1987), L1320), this device is constructed using an MgO substrate 11. Y,
Ba, Cu, Ox superconducting thin film 12. It is composed of a CdS photoconductive thin film 13, an electrode 14, and an optical fiber 15. The superconducting thin film 12 here is formed by heat treatment after being formed using a high frequency sputtering method, and is said to have a thickness of 2 μm and a critical temperature of 85K. A groove with a width of 8II11 and a depth of 5 μm is previously provided in the center of the superconducting thin film 12, and the thickness of the superconducting thin film attached to the bottom edge of this groove is 0.5 μl or less. This portion is called a weak coupling portion, and a CdS thin film 13 is further applied thereon to a thickness of 0.2 μm by vacuum evaporation. When a current is passed through the electrode 14 provided on the top of the superconducting thin film 12, it initially flows at a voltage of O, but as the current value increases, the voltage increases as the current increases. When irradiated with light having a wavelength of 0.35 .mu.l to 0.8 .mu.l, the current value decreases compared to before irradiation. This effect is used for switching operation. FIG. 4 shows the current-voltage characteristics of the switch element shown in FIG. 3. Fourth
In the figure, a is before irradiation and b is after irradiation.

However, the switch element adopting the structure shown in Fig. 3 does not necessarily have good IV characteristics before and after irradiation with light, and therefore there is room for improvement in dealing with 0N-OFF operation. left behind.

[Problems to be solved by the invention] The present invention utilizes the characteristics of superconductors, such as low power consumption and high-speed response, to provide a novel device (superconducting switch element) using an oxide high-temperature superconductor. The purpose is to

[Means to solve the problem]

In the superconducting switch element of the present invention, a superconducting thin film is formed in the plane direction by sandwiching a non-magnetic metal or alloy thin film (junction) on an insulating substrate, and electrodes are placed on the superconducting thin film on both sides of the junction. is formed, an insulating film is further formed on these, and a superconducting conductive wire for applying a magnetic field is provided on the insulating film in proximity to the junction.

The present invention will be explained in more detail below with reference to the drawings.

To put it simply, the switch element of the present invention is made of insulating ceramic tMg (LSrTiO
, etc., a bonding portion 2 formed of a non-magnetic metal (alloy) thin film, a superconducting thin film 3 attached to separate the bonding portion 2, and a superconducting conductive wire 4 for applying a magnetic field.
In addition, In or Au electrode 5.5 int film 6 (insulating film)
It has been established.

The superconducting thin film 3 has a
Cu.

Ox, LnlBa, Cu30x (Ln=Nd, Sm
, Eu, Gd, Dy, Ha, Er, Tm,
Yb, etc.), or Bi, Sr, Ca, Cu30x,
T12Ha2Ca, Cu, Ox superconductor, and the metal or alloy thin film used for the joint part 2 includes Nb, Zn, A1. There are Cu-A1 and the like. As for the method for producing the superconducting thin film 3.

Sputtering method, vapor deposition (resistance heating, electron beam) method,
Ion blating method, MB2 method or thermal decomposition method,
Spray pyrosis method, plasma CVD method and other methods are used. Also, non-magnetic metal (alloy) thin film 2.5i
The 02 Wt film 6 and the superconducting wire 4 for applying a magnetic field are preferably produced using a sputtering method or a vapor deposition method. In this case,
The superconducting wire 4 is made of oxide.

The thickness of the superconducting thin film 3 is preferably 0.5 μl to 12 μm, the thickness of the metal or alloy thin film 2 is similarly 0.5 μl to 2 μm, and the width of the joint 2 is preferably 0.2 μl to 1 μm.
, the membrane 6 and the superconducting wire 4 each have a thickness of 0.2 to 0.5 μ, and a wire width of 0°2 to 0.5 μ. Two superconducting conductive wires 4 for applying a magnetic field are attached approximately on the joint portion 2 at an interval of about 0.5 μm.

The joint portion 2 and the conductive wire 4 are manufactured using a photolithography method.

Next, the operating principle of the switch element of the present invention will be explained.

In a superconducting state, when a current is passed from the electrode 5, the superconducting current leaks into the non-magnetic metal or alloy thin film 2 side.
Due to the "proximity effect", current flows from the superconductor (superconducting thin film 3) to the other superconducting thin film 3 via the non-magnetic metal or alloy thin film 2.This superconducting current flows at zero voltage up to a certain value. (maximum zero voltage current), the voltage begins to increase as the current increases, resulting in a current-voltage characteristic curve as shown in FIG.

Next, currents are applied in opposite directions to the two superconducting conductive wires 4 provided in parallel to each other to generate a magnetic field. The magnitude of the magnetic field is preferably below the lower critical magnetic field of the superconductor, for example Y1
In the case of Ba2Cu and Ox, it is about 1000e or less.

Further, it is necessary that the magnitude of the conductor current required to generate the magnetic field does not exceed the critical current value of the superconductor. The applied magnetic field concentrates on the junction 2, and the current flowing through the junction 2 decreases due to the magnetoresistive effect caused by this magnetic field, showing a curve as shown in FIG. Current (voltage) before and after applying magnetic field
The change corresponds to ON-OFF operation, and switching operation is performed.

〔Example〕

Er-
A Ba-Cu-0 superconducting thin film was provided. The target composition was set to be close to Er:Ba:Cu=1:2:3, and after depositing a film with a thickness of approximately 1.2 μm in a mixed gas atmosphere of Ar and oxygen at a substrate temperature of approximately 500°C, Annealing was performed at 900° C. for 2 hours in an oxygen atmosphere using a furnace. The film was oriented along the C-axis and exhibited a critical temperature of 84K.

Next, the superconducting film was patterned using a photoresist method so that a gap of about 1.2 μm in width was formed at the center of the film, and the superconducting film was removed by wet etching. However, avoid using wet materials that contain water.

Then, Nb is applied as a metal thin film to this groove. The metal film was formed to a thickness of about 1.5 μm by DC magnetron sputtering in an Ar gas atmosphere at a substrate temperature of about 350° C. to form a bonding portion. The Nb film was a C-axis oriented film. A mask is placed on the edge of the surface of this material, and a Si film with a thickness of approximately 0°2 μm is placed.
n. A film was formed by a vacuum evaporation method to serve as a protective film. The part of the mask that does not have a membrane is the part where the electrodes are attached.
Its width is approximately 2-3II11. Next, a superconducting wire with a width of about 0.2 μm and a thickness of about 2 μm is placed on the joint.
■Two wires were attached in parallel at intervals. The same Er-based superconductor as above was used for this superconducting wire.

This differs from the previous method because the film is fabricated on SiO□.

After forming an amorphous film without heating the substrate, the film is crystallized by laser annealing. This film is a polycrystalline film, with Jc of approximately 10'A/a# and Tc of approximately 80
It was close to. Then, a conductive wire pattern was created using a photoresist method.

Finally, an Au electrode was fabricated by the spuck method to form a device.

The current-voltage curve when a current was passed through the electrodes and no magnetic field was generated was as shown in Figure 2a. However, the temperature around the element was 77°C. Next, attach two wires to each conductor in opposite directions.
When a current of ~3 A was applied and a magnetic field of about 6006 mm was applied, a current was passed through the electrodes and the current-voltage characteristics were measured, resulting in a curve as shown in Figure 2. a to ON state, b
By turning OFF, switching operation can be performed.

〔Effect of the invention〕

As can be seen from FIG. 2, a switch element made with a specific structure using the oxide-based high temperature superconductor of the present invention has low power consumption and excellent high-speed response.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the main parts of a superconducting switch element according to the present invention, and FIG. 2 is a characteristic diagram of this switch element. Figure 3 is a schematic diagram of the main parts of a conventional superconducting switch element.
FIG. 4 is a characteristic diagram of the conventional switch element. l...Insulating substrate 2...Joint part (non-magnetic metal or alloy thin film) 3...Superconducting thin film 4...Superconducting conductor wire for magnetic field application 5...Electrode 6...Insulating film ( Protective film)

Claims (1)

[Claims] (1) A superconducting thin film is formed in the plane direction by sandwiching a nonmagnetic metal or alloy thin film on an insulating substrate, and electrodes are formed on the superconducting thin film on both sides of the joint, and further insulated on top of these. 1. A superconducting switch element comprising: a film formed thereon; and a superconducting wire for applying a magnetic field provided on the insulating film so as to be close to the junction.