JP2596337B2 - Superconducting element - Google Patents

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 a high-speed digital circuit, an analog data processing circuit, a sensor circuit device, and a small magnetic field signal detecting device, which exhibit a specific performance by using superconductivity. In particular, the present invention relates to an operation method and an element structure of a superconducting element having high speed and low power consumption.

[0002]

2. Description of the Related Art As a conventional superconducting element, an element of an operation system corresponding to a semiconductor field-effect transistor and a bipolar transistor has been obtained. A superconducting field effect transistor controls the amplitude of superconducting current between a source and a drain electrode by a gate voltage, and a superconducting bipolar transistor uses a quasiparticle current, that is, a normal conducting current, as a superconducting base. The voltage is controlled by a voltage bias to the negative electrode. Among these, 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 when a superconductor and a normal conductor come into contact with each other, a superconducting carrier seeps out of the superconductor into the normal conductor. Therefore, when two superconducting electrodes are connected via the normal conductive layer,
A superconducting current flows between the superconducting poles. The 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 described in H.-J. Takayanagi Physical Review Letter 54, p2449-p2452, 1985. The above-described transistor is manufactured using InAs for the normal conductive layer and Nb for the superconducting layer, and the operation is realized.

[0003]

The superconducting field-effect transistor described in the section of the prior art has the following problems. That is, the distance over which the superconducting carrier permeates 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 attenuation 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 as 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 the superconducting carriers exuded by the proximity effect decreases exponentially at the interface between the superconductor and the normal conductor, in units of the superconducting decay length. Conversely, in order to obtain a field-effect transistor as an element having a gain for a switching circuit, the length of the gate electrode and the like must necessarily be set to submicron dimensions.

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

[0005]

The object of the present invention is to provide a superconductive source electrode 1 and a drain electrode 4 as shown in FIG. 1 or 3, and a one-dimensional array between a source electrode and a drain electrode. Alternatively, a channel composed of a group of a plurality of superconductors 2 arranged in a two-dimensional plane, a gate insulating film 10 disposed in contact with the channel, and a gate electrode disposed in contact with the gate insulating film 11 and a substrate 3 on which a plurality of superconductors constituting a channel are deposited and which has a finite electric conductivity, and all or a part of the superconductor constituting the channel is provided via a gate insulating film. This is attained by a structure in which all or at least a part of the superconductor overlapping the gate electrode and constituting the channel has a structure exhibiting superconductivity during operation of the device.

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

Further, when a plurality of superconductors constituting the source and drain electrodes and the channel are composed of a Cu-based oxide superconductor, Cu is used between the plurality of superconductors constituting the channel of the superconducting element. The structure is such that the oxides are electrically coupled by a normal conductor.

In the case where the plurality of superconductors constituting the source and drain electrodes and the channel are made of a Cu-based oxide superconductor, the plurality of superconductors constituting the channel are usually made of a semiconductor or an oxide containing Cu. The superconductor is arranged on a conductor substrate, and the substrate is electrically connected to the superconductor.

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

Further, a plurality of superconductors constituting a channel overlap with a gate electrode via a gate insulating film, a plurality of superconductors constituting a channel are provided, and a finite electric conductivity is provided. The substrate has a structure in which a region is present between the source and drain electrodes and does not overlap with any of the source and drain electrodes and the gate electrode.

The switching operation of the superconducting element having the above structure is realized by a gate voltage signal that realizes a state where the phase of the superconducting waveguide function is relatively determined between both ends of the channel and a state where the phase is more uncertain. ,
Basically, the superconducting current that can flow between the source and drain electrodes is controlled. The gate voltage signal does not act on a plurality of superconducting electrodes constituting a channel, but is applied to a substrate to which the superconductor is electrically connected.

[0012]

In the present invention, as shown in FIG. 2, when a large number of superconductors are connected in parallel and in series by a resistor, the presence or absence of superconducting current depends not only on the resistance value but also on the superconductors connected in series or in parallel. Also depends on the number of superconductors connected to the superconductor. The magnitude of the superconducting current obtained at both ends of the matrix depends on the fluctuation of the phase of the superconducting waveguide function that forms 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 the number of series connection is reduced and the parallel connection component is sufficiently increased,
Phase fluctuations at both ends of the superconducting train are suppressed, and a superconducting current is obtained.

The presence or absence of the superconducting current due to the above matrix structure can be adjusted by an external control signal even if the shape and configuration of the matrix are fixed.
A switching operation is provided.

[0014]

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

A single crystal of SrTi oxide is used as the substrate material 9 and the composition ratio of the metal element on the SrTi oxide substrate is 1:
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. For the PrBaCu oxide thin film, a transfer pattern is formed by an electron beam lithography 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.
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 a source electrode 1, a drain electrode 4, and a channel superconducting layer 2.
The atmosphere gas at the time of film formation is a mixed gas of argon and oxygen,
The thickness is 100 nm. The HoBaCu oxide thin film is formed with a transfer pattern by an electron beam lithography apparatus using an organic resist film, and the source electrode, the drain electrode, and the channel superconductivity of the superconducting element by an ion beam etching method using Ar gas. A layer pattern is formed. The channel superconducting layer has a particularly fine pattern, and the size and spacing of the superconducting dots are reduced from 0.05 μm to 0.5 μm.
Submicron down to microns. Next, an SrTi oxide thin film is formed by a laser deposition method, and a gate insulating film 1 is formed.
Set to 0. Laser deposition is performed in an oxygen gas atmosphere and Sr
The thickness of the Ti 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 an ion beam using Ar gas is used.
Gate insulating film pattern of superconducting element by
Is formed. Further, the gate electrode 11 is
Is formed by an organic resist, an Au thin film is formed thereon by a vacuum evaporation 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 element manufactured by this method is the sixth type.
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 and the positive electrode is applied to the gate electrode. When a positive electric field is applied to the channel layer, the superconducting current flowing between the source and the drain decreases. Therefore, the present superconducting element can control the superconducting current by the gate voltage. (Embodiment 2) Embodiment 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 with a metal element composition ratio of 1: 2: 3
An oxide superconducting thin film is formed by a high-frequency magnetron sputtering method. Gate electrode 11 made of organic resist
Is formed, and the pattern is transferred to the HoBaCu oxide superconducting thin film by an ion beam etching method using Ar gas. The gate electrode is located between the source and the drain, and is arranged below a row of micro superconducting regions arranged in the width direction of the channel.

Next, an SrTi oxide thin film is formed by a laser vapor deposition method to form a gate insulating film 10. Laser deposition was performed in an oxygen gas atmosphere, and the thickness of the SrTi oxide was 30
It is set to 0 nm. For the SrTi oxide thin film, a transfer pattern is formed by an electron beam lithography 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. Done.

Further, H having a metal element composition ratio of 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 a source electrode 1, a drain electrode 4, and a channel superconducting layer 2. The atmosphere gas at the time of film formation is a mixed gas of argon and oxygen, and the film thickness is 100 nm. H
The oBaCu oxide thin film is formed with a transfer pattern by an electron beam lithography apparatus using an organic resist film, and a source electrode, a drain electrode, and a channel superconducting element of a superconducting element by an ion beam etching method using Ar gas. A layer pattern is formed. The channel superconducting layer has a particularly fine pattern, and the size and spacing of the superconducting dots are reduced by 0.0.
Submicron from 5 microns to 0.5 microns.

On this, a PrBaCu oxide thin film having a metal element composition ratio of 1: 2: 3 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. For the PrBaCu oxide thin film, a transfer pattern is formed by an electron beam lithography 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. You.

The superconducting element manufactured by this method is the sixth type.
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, and a positive voltage is applied to the gate electrode. Is applied, and when a positive electric field is applied to the channel layer, the superconducting current flowing between the source and the drain decreases. 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 on the SrTi oxide substrate is 1.
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 transfer pattern of the LaBaCu oxide thin film is formed by an electron beam lithography apparatus using an organic resist film, and the channel underlayer pattern of the superconducting element is formed by an ion beam etching method using Ar gas. You.

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 at the time of film formation is a mixed gas of argon and oxygen, and the film thickness is 100 nm. The HoBaCu oxide thin film is formed with a transfer pattern by an electron beam lithography apparatus using an organic resist film, and the source electrode, the drain electrode, and the channel superconductivity of the superconducting element by an ion beam etching method using Ar gas. A layer pattern is formed. The channel superconducting layer has a particularly fine pattern, and the size and spacing of the superconducting dots are in the submicron range of 0.05 to 0.5 microns. Next, an 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 thickness of the 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. Will be

Further, H having a metal element composition ratio of 1: 2: 3
An oBaCu oxide superconducting thin film is formed by a high-frequency magnetron sputtering method. Organic resist
Then, a pattern is formed on the HoBaCu oxide superconducting thin film by an ion beam etching method using Ar gas.

The wiring between the superconducting elements is made of a HoBaCu oxide superconducting thin film, and the gate electrode and the source,
A 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 formed. 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 element, the recombination time of carriers in which a superconducting pair is generated from quasiparticles or the time in which a superconducting pair is broken into quasiparticles is excluded from the switching time, and the conventional superconducting three-terminal is used. Switching speed is improved as compared with the element.

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

[Brief description of the 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 shows voltage-current characteristics 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 ... minute superconducting region, 3 ... normal conductive layer, 4 ... drain, 5 ... phase, 6 ... superconducting electrode,
7: resistance, 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.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Tsukamoto 1-280 Higashi Koigakubo, Kokubunji, Tokyo, Japan Inside the Central Research Laboratory, Hitachi, Ltd. (72) Inventor Shoichi Akamatsu 1-280 Higashi Koigakubo, Kokubunji, Tokyo Inside the Central Research Laboratory (72) Inventor Masakuni Okamoto 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory Hitachi, Ltd. (72) Kazumasa Takagi 1-1280 Higashi Koikekubo, Kokubunji-shi, Tokyo Hitachi Central, Ltd. (56) References JP-A-61-206278 (JP, A) JP-A-4-118977 (JP, A)

Claims (5)

(57) [Claims] 1. A semiconductor device comprising: a channel layer made of a normal conductor; a source electrode and a drain electrode made of a superconductor formed separately on the channel layer; and a region formed between the source electrode and the drain electrode of the channel layer. A plurality of dot-shaped regions formed of a superconductor joined to the upper surface of the substrate, and an insulating film on the channel layer and a gate electrode for applying an electric field through at least one of the dot-shaped regions; Have dimensions of 0.05 to 0.5 microns, respectively, and are two-dimensionally provided on the upper surface between the electrode forming regions at an interval of 0.05 to 0.5 microns. Characteristic superconducting element. 2. The method according to claim 1, wherein said dot-shaped regions are electrically connected by a semiconductor.
A superconducting element according to the item. 3. The superconducting element according to claim 1, wherein said dot-shaped regions are electrically connected by a normal conductor of an oxide containing Cu. 4. The superconducting element according to claim 1, wherein said dot-like region and said channel layer are formed of an oxide having the same crystal structure. 5. A superconducting element according to claim 1, wherein a plurality of superconducting wirings and resistors are mounted on one substrate together with a superconducting integrated circuit having a switching function. Superconducting element.