JPH07106647A - Superconducting element - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a superconducting transistor operating method and structure which can obtain a superconducting current for any gate length and whose device dimensions are not restricted by the constraint of the superconducting decay length due to the proximity effect. The purpose is to [Structure] A source electrode and a drain electrode formed on a substrate, a normal conductive layer formed above or below the source electrode and the drain electrode, and a gate on the surface opposite to the normal conductive layer of the source electrode and the drain electrode. In a superconducting element consisting of a gate electrode formed via an insulating film, a channel is formed between a plurality of superconductors arranged in a one-dimensional array or a two-dimensional plane between the source electrode and the drain electrode. It is achieved by [Effect] In the present superconducting device, switching of the superconducting device is realized without being restricted by the size of the gate electrode, and the recombination time of carriers in which the superconducting pair is generated from the quasiparticles, or the superconducting pair is reduced. The time for breaking into quasi-particles is excluded from the switching time, and the switching speed is improved as compared with the conventional superconducting three-terminal element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of superconducting electronics, such as high-speed digital circuits, analog data processing circuits, sensor circuit devices, and minute magnetic field signal detecting devices, which exhibit unique performance by using superconductivity. In particular, the present invention relates to an operation system and a device structure of a superconducting device having high speed and low power consumption.

[0002]

2. Description of the Related Art As a conventional superconducting element, an element having an operation system corresponding to a semiconductor field effect transistor and a bipolar transistor has been obtained. The superconducting field-effect transistor controls the amplitude of the superconducting current between the source and drain electrodes by the gate voltage.The superconducting bipolar transistor determines the quasi-particle current, that is, the value of the normal conducting current. -It is controlled by the voltage bias with respect to the voltage. Among them, the superconducting field effect transistor utilizes the proximity effect of superconductivity and the proximity effect on the carrier distribution of the normal conductive layer. The proximity effect is a phenomenon in which a superconducting carrier exudes from the superconductor into the normal conductor when the superconductor and the normal conductor come into contact with each other. Therefore, if two superconducting electrodes are connected through the normal conductive layer,
A superconducting current flows between the superconducting electrodes. This superconducting current is controlled by applying a gate voltage by the electric field effect. A superconducting field effect transistor having such an operation method is disclosed in Takayanagi Physical Review Letter, Vol. 54, p2449 to p2452, 1985. The transistor is manufactured by using InAs for the normal conductive layer and Nb for the superconducting layer to realize the operation.

[0003]

The superconducting field effect transistor described in the above section of the prior art has the following problems. That is, the distance by which the superconducting carriers seep into the normal conductive layer due to the proximity effect, that is, the superconducting decay length is about 0.1 micrometer. Therefore, in order to obtain a superconducting current between the electrodes, it is necessary to keep the distance between the electrodes at a submicron size. For example, in the conventional superconducting field effect transistor using InAs for the normal conductive layer, the distance between the source and drain electrodes is set to 0.4 micrometer. When the distance between the electrodes is sufficiently longer than the superconducting decay length, the amplitude of the superconducting current decreases. Even if the carrier concentration is increased by a high gate voltage, it does not reach the value expected for the superconducting current, that is, the value obtained by dividing the gap voltage of the superconducting electrode by the element resistance. The reason for this is that the density of superconducting carriers exuded by the proximity effect exponentially decreases at the interface between the superconductor and the normal conductor in units of the superconducting decay length. On the contrary, in order to obtain a field effect transistor as an element having a gain for a switching circuit, it is necessary to make the length of the gate electrode or the like sub-micron in size.

Therefore, an object of the present invention is to provide a superconducting transistor operating system and structure in which a superconducting current can be obtained for an arbitrary gate length in a superconducting element and the element size is not restricted by the restriction of the superconducting attenuation length due to the proximity effect. To give.

[0005]

The above-mentioned object is to provide a one-dimensional array, as shown in FIG. 1 or 3, in which a superconducting source electrode 1 and a drain electrode 4, and a source electrode and a drain electrode are provided. Alternatively, a channel composed of a group of a plurality of superconductors 2 arranged in a two-dimensional plane, a gate insulating film 10 arranged in contact with the channel, and a gate electrode arranged in contact with the gate insulating film. 11 and a plurality of superconductors forming a channel and consisting of a substrate 3 having a finite electric conductivity, and the whole or a part of the superconductor forming the channel is interposed through the gate insulating film. This is achieved by having a structure in which all or at least a part of the superconductor which overlaps with the gate electrode and constitutes the channel has a superconducting property when the device operates.

The above object can also be achieved by having the following structure. The plurality of superconductors forming the channel are electrically coupled by a semiconductor substrate having a characteristic that the temperature coefficient of resistance is negative, that is, the resistance value increases as the temperature decreases.

Further, when the source and drain electrodes, and further, the plurality of superconductors forming the channel are formed of Cu-based oxide superconductor, Cu is contained between the plurality of superconductors forming the channel of the superconducting element. The structure is such that it is electrically coupled by the normal conductor of the oxide contained therein.

When the source and drain electrodes and the plurality of superconductors forming the channel are formed of Cu-based oxide superconductors, the plurality of superconductors forming the channel are usually semiconductors or oxides containing Cu. The conductors are arranged on the substrate, and the superconductor and these substrates are electrically connected.

When a plurality of superconductors forming a channel are arranged on a substrate of an oxide semiconductor or an oxide normal conductor containing Cu, the oxide-based superconductor and the oxide substrate have the same crystal. The structure has a structure in which the superconductor and these substrates are electrically connected.

Further, a part of the plurality of superconductors forming the channel overlaps the gate electrode through the gate insulating film, the plurality of superconductors forming the channel are arranged, and a finite electric conductivity is provided. In the substrate having the structure, there is a region between the source and drain electrodes, which does not overlap with the source or drain electrode or the gate electrode.

The switching operation in the superconducting device having the above structure is achieved by the gate voltage signal realizing a state in which the phase of the superconducting waveguide function is relatively fixed between both ends of the channel and a more indeterminate state. ,
It is basically to control the superconducting current that can flow between the source and drain electrodes. The gate voltage signal does not act on the plurality of superconducting electrodes forming the channel, but is applied to the substrate to which the superconductor is electrically connected.

[0012]

According to the present invention, as shown in FIG. 2, when a large number of superconductors are connected in parallel and in series by resistors, the presence or absence of superconducting current is not limited to the resistance value, but the superconductors connected in series or in parallel. It also depends on the number of superconductors connected to. The magnitude of the superconducting current obtained at both ends of the matrix depends on the phase fluctuation of the superconducting waveguiding function that composes the superconducting current. That is, when the superconductors are connected in series, the phase fluctuation is enlarged at both ends of the superconductor row, and the superconducting current cannot be obtained. On the other hand, if you reduce the number of series connections and increase the number of parallel connection components sufficiently,
Phase fluctuations at both ends of the superconducting train are suppressed, and superconducting current is obtained.

The presence or absence of the superconducting current due to the matrix structure as described above can be adjusted by a control signal from the outside even if the shape and configuration of the matrix are fixed,
Switching action is provided.

[0014]

(Embodiment 1) Embodiment 1 of the present invention will be described with reference to FIGS. 3, 4, and 5.

A single crystal of SrTi oxide is used as the substrate material 9, and the composition ratio of the metal element is 1: on the SrTi oxide substrate.
A 2: 3 PrBaCu oxide thin film is formed by a high frequency magnetron sputtering method to form a channel underlayer 3. The atmosphere gas at the time of film formation is a mixed gas of argon and oxygen, and the film thickness is 300 nm. The PrBaCu oxide thin film is used to form a transfer pattern by an electron beam drawing apparatus using an organic resist film and a channel underlayer pattern of a superconducting element by an ion beam etching method using Ar gas.
Is formed.

Next, a HoBaCu oxide superconducting thin film having a metal element composition ratio of 1: 2: 3 is formed on the PrBaCu oxide thin film by a high frequency magnetron sputtering method. This oxide superconducting thin film is commonly used as the source electrode 1, the drain electrode 4, and the channel superconducting layer 2.
The atmosphere gas during film formation was a mixed gas of argon and oxygen,
The film thickness is 100 nm. The HoBaCu oxide thin film is a transfer pattern formed by an electron beam drawing apparatus using an organic resist film, and a source electrode, a drain electrode, and a channel superconductivity of a superconducting element by an ion beam etching method using Ar gas. Formation of the layer pattern is performed. In the channel superconducting layer, the pattern is particularly miniaturized, and the size and spacing of the superconducting dots are set to 0.05 μm to 0.5 μm.
Submicron up to micron. Next, a SrTi oxide thin film is formed by a laser deposition method to form a gate insulating film 1.
Set to 0. Laser deposition is carried out in an oxygen gas atmosphere with Sr.
The film thickness of the Ti oxide is 300 nm. The SrTi oxide thin film is used to form a pattern for transfer by an optical exposure apparatus using an organic resist film, and an ion beam using Ar gas.
Gate insulating film pattern of superconducting device
Formation is performed. Further, the gate electrode 11
The reverse pattern is formed by an organic resist, an Au thin film is formed thereon by a vacuum deposition method, and a lift-off process is performed to obtain a gate electrode. The gate electrode has a structure that covers the whole or a part of the channel layer between the source and the drain.

The superconducting device manufactured by this method is
As shown in the figure, when a negative voltage is applied to the gate electrode and a negative electric field is applied to the channel layer, the superconducting current flowing between the source and the drain increases at 21 and the positive electric field is applied to the gate electrode. When a positive electric field is applied to the channel layer by applying the voltage of, the superconducting current flowing between the source and the drain is reduced at 22. Therefore, the present superconducting element can control the superconducting current by the gate voltage. (Example 2) Example 2 of the present invention
Will be described with reference to FIG.

A single crystal of SrTi oxide 9 is used as a substrate material. HoBaCu in which the composition ratio of metal elements is 1: 2: 3
An oxide superconducting thin film is formed by a high frequency magnetron sputtering method. Gate electrode 11 with organic resist
And the pattern is transferred to the HoBaCu oxide superconducting thin film by the ion beam etching method using Ar gas. The gate electrode is located between the source and the drain, and is arranged at the bottom of the row of minute superconducting regions arranged in the width direction of the channel.

Next, a SrTi oxide thin film is formed by laser vapor deposition to form a gate insulating film 10. Laser deposition is performed in an oxygen gas atmosphere, and the film thickness of SrTi oxide is 30.
0 nm. The SrTi oxide thin film has a transfer pattern formed by an electron beam drawing apparatus using an organic resist film, and a gate insulating film pattern for a superconducting element formed by an ion beam etching method using Ar gas. Done.

Further, the composition ratio of metal elements is H in which the composition ratio is 1: 2: 3.
An oBaCu oxide superconducting thin film is formed by a high frequency magnetron sputtering method. This oxide superconducting thin film is commonly used as the source electrode 1, the drain electrode 4, and the channel superconducting layer 2. The atmosphere gas during film formation is a mixed gas of argon and oxygen, and the film thickness is 100 nm. H
The oBaCu oxide thin film is a source pattern, a drain electrode, and a channel superconducting element of a superconducting element formed by an electron beam drawing apparatus using an organic resist film for forming a transfer pattern and an ion beam etching method using Ar gas. Formation of the layer pattern is performed. In the channel superconducting layer, the pattern is particularly miniaturized, and the size and spacing of the superconducting dots are set to 0.0.
Submicron from 5 microns to 0.5 microns.

A PrBaCu oxide thin film having a metal element composition ratio of 1: 2: 3 is formed thereon by a high frequency magnetron sputtering method to form a channel underlayer 3. The atmosphere gas at the time of film formation is a mixed gas of argon and oxygen, and the film thickness is 300 nm. On the PrBaCu oxide thin film, a transfer pattern is formed by an electron beam drawing apparatus using an organic resist film, and a channel underlayer pattern of a superconducting element is formed by an ion beam etching method using Ar gas. It

The superconducting device manufactured by this method is
As in the figure, when a negative voltage is applied to the gate electrode and a negative electric field is applied to the channel layer, the superconducting current flowing between the source and drain increases, and a positive voltage is applied to the gate electrode. Is applied and a positive electric field is applied to the channel layer, the superconducting current flowing between the source and the drain is reduced. Therefore, the present superconducting element can control the superconducting current by the gate voltage.

(Embodiment 3) A third embodiment of the present invention will be described with reference to FIG.

A single crystal of SrTi oxide is used as the substrate material, and the composition ratio of the metal element is 1. on the SrTi oxide substrate.
A 5: 1.5: 3 LaBaCu oxide thin film is formed by a high frequency magnetron sputtering method to form a channel underlayer. The atmosphere gas at the time of film formation is a mixed gas of argon and oxygen, and the film thickness is 300 nm. The LaBaCu oxide thin film is formed with a transfer pattern by an electron beam drawing apparatus using an organic resist film and a channel underlayer pattern of a superconducting element by an ion beam etching method using Ar gas. It

Next, a HoBaCu oxide superconducting thin film having a metal element composition ratio of 1: 2: 3 is formed on the LaBaCu oxide thin film by a high frequency magnetron sputtering method. This oxide superconducting thin film is commonly used as a source electrode, a drain electrode, and a channel superconducting layer. The atmosphere gas during film formation is a mixed gas of argon and oxygen, and the film thickness is 100 nm. The HoBaCu oxide thin film is a transfer pattern formed by an electron beam drawing apparatus using an organic resist film, and a source electrode, a drain electrode, and a channel superconductivity of a superconducting element by an ion beam etching method using Ar gas. Formation of the layer pattern is performed. In the channel superconducting layer, the pattern is particularly miniaturized, and the superconducting dots are dimensioned and spaced from 0.05 micron to 0.5 micron submicron. Next, a SrTi oxide thin film is formed by a laser deposition method to form a gate insulating film. Laser deposition is performed in an oxygen gas atmosphere, and the film thickness of SrTi oxide is 300 nm. For the SrTi oxide thin film, a transfer pattern is formed by an optical exposure apparatus using an organic resist film, and a gate insulating film pattern of a superconducting element is formed by an ion beam etching method using Ar gas. Be seen.

Further, H having a composition ratio of metal elements of 1: 2: 3
An oBaCu oxide superconducting thin film is formed by a high frequency magnetron sputtering method. With an organic resist
A pattern is formed as a cathode electrode, and the pattern is transferred to the HoBaCu oxide superconducting thin film by an ion beam etching method using Ar gas.

Wiring between the superconducting elements is made of a HoBaCu oxide superconducting thin film, and a gate electrode and a source,
The HoBaCu oxide superconducting thin film common to the drain electrode is used for the wiring film.

According to this method, an inverter circuit composed of two superconducting elements and a resistor is constructed. The resistance element is made of an Au thin film. The inverter circuit correctly outputs an inverted signal with respect to the input signal.

[0029]

The present invention has the following effects.

(1) In the present superconducting device, the recombination time of carriers in which a superconducting pair is generated from a quasi-particle, or the time when the superconducting pair is destroyed to become a quasi-particle is excluded from the switching time. The switching speed is improved as compared with the device.

(2) Switching of the superconducting element is realized without being restricted by the size of the gate electrode.

[Brief description of drawings]

FIG. 1 is a schematic view of a superconducting element according to the present invention.

FIG. 2 is an equivalent circuit of a superconducting element according to the present invention.

FIG. 3 is a structural diagram 1 of a superconducting element according to the present invention.

FIG. 4 is a structural diagram 2 of a superconducting element according to the present invention.

FIG. 5 is a structural diagram 3 of a superconducting element according to the present invention.

FIG. 6 is a voltage-current characteristic of a superconducting element.

FIG. 7 is a structural diagram 4 of a superconducting element according to the present invention.

FIG. 8 is an inverter circuit using a superconducting element according to the present invention.

[Explanation of symbols]

1 ... Source, 2 ... Small superconducting region, 3 ... Normal conductive layer, 4 ... Drain, 5 ... Phase, 6 ... Superconducting electrode,
7 ... Resistor, 8 ... Josephson coupling, 9 ... Substrate, 1
0 ... Gate insulating film, 11 ... Gate electrode, 20 ... Gate voltage zero, 21 ... Gate voltage negative, 22 ... Gate voltage positive, 31 ... Superconducting element.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Tsukamoto 1-280, Higashi Koikeku, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor Shoichi Akamatsu 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. Central Research Laboratory (72) Inventor Masakuni Okamoto 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Central Research Institute (72) Inventor Kazumasa Takagi 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Central In the laboratory

Claims (8)

[Claims] 1. A source electrode and a drain electrode formed on a substrate, a normal conductive layer formed above or below the source electrode and the drain electrode, and a surface opposite to the normal conductive layer of the source electrode and the drain electrode. A superconducting element comprising a gate electrode formed via a gate insulating film, and a channel comprising a group of a plurality of superconductors arranged in a one-dimensional array or two-dimensional plane between the source electrode and the drain electrode. Forming a superconducting element. 2. A superconducting element according to claim 1, wherein a plurality of superconductors forming a channel are electrically coupled by a semiconductor. 3. The superconducting element according to claim 1, wherein a plurality of superconductors forming a channel are electrically coupled by a normal conductor of an oxide containing Cu. And superconducting element. 4. A superconductor according to claim 1, wherein a plurality of superconductors forming a channel are arranged on a substrate of an oxide semiconductor or an oxide normal conductor containing Cu. A superconducting device characterized in that these substrates are electrically connected to each other. 5. The superconducting element according to claim 1 or 2, wherein the plurality of superconductors constituting the channel are made of oxide, and the normal conductivity of the oxide semiconductor or the oxide containing Cu. A superconducting element arranged on a body substrate, wherein the oxide-based superconductor and the oxide substrate have the same crystal structure, and the superconductor and these substrates are electrically connected. 6. The superconducting device according to claim 1, wherein a gate voltage signal causes a state in which the phase of the superconducting waveguide function is relatively fixed and a state in which it is more uncertain between the two ends of the channel. When realized, a superconducting device capable of controlling a superconducting current flowing between a source and a drain electrode. 7. The superconducting device according to claim 1, wherein a part of a plurality of superconductors forming a channel overlaps with the gate electrode via the gate insulating film, and further, In a substrate having a plurality of superconductors forming a channel and having a finite electric conductivity, it is located between the source and drain electrodes, and the source and drain electrodes as well as the gate electrode are provided. A superconducting element characterized by having non-overlapping regions. 8. The superconducting element according to claim 1, wherein a plurality of superconducting wirings and resistors are mounted on a single substrate together with a superconducting wiring to form a superconducting integrated circuit having a switching function. Superconducting element.