JPH04134881A - Superconducting device and manufacture thereof - Google Patents

Abstract

PURPOSE:To make it possible to eliminate the need for a fine processing technology and prepare a high performance device which uses an oxide superconductor by controlling a superconducting current flowing in a superconducting circuit with gate voltage. CONSTITUTION:A gate electrode 4 is installed to a superconducting device in order to control a superconducting channel 10 by an oxide superconductor, a source electrode 2 which passes electric current thereto, a drain electrode 3, and electric current flowing in the superconducting channel. The main current flows in the superconductor. The superconducting channel is turned on and off with the voltage applied to the gate electrode 4. Energy is applied to a part which forms a superconducting channel for a thin film 1 by using focusing ion beam, laser or the like so that the component elements of a substrate 5 located below may be diffused, thereby forming a non-superconducting region in the thin film 1. This construction makes it possible to produce the superconducting channel from the superconductive portion whose thickness is reduced.

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 with a novel configuration and a method for manufacturing the same.

A Josephson device is a typical device using conventional technology superconductivity. A Josephson device has a configuration in which a pair of superconductors are coupled via a tunnel barrier, and is capable of high-speed switching operation. However, the Josephson element is 2
It is a terminal element and requires a complicated circuit configuration to realize a logic circuit.

On the other hand, three-terminal elements using superconductivity include superconducting base transistors, superconducting FETs, and the like. In Figure 3,
A conceptual diagram of a superconducting base transistor is shown. The superconducting base transistor shown in FIG. 3 is composed of an emitter 21 made of a superconductor or a normal conductor, a tunnel barrier 22 made of an insulator, a base 23 made of a superconductor, a semiconductor isolator 24, and a normal conductor. collector 2
It has a structure in which 5 layers are stacked. This superconducting base transistor is a low-power consumption, high-speed operation element that utilizes high-speed electrons that have passed through the tunnel barrier 22.

FIG. 4 shows a conceptual diagram of a superconducting FET. In the superconducting FET of FIG. 4, a superconducting source electrode 41 and a superconducting drain electrode 42 made of a superconductor are connected to a semiconductor layer 43
are placed close to each other on top. The semiconductor layer 43 in the portion between the superconducting source electrode 41 and the superconducting drain electrode 42 has its lower side largely shaved and has a reduced thickness.

Further, a gate insulating film 46 is formed on the lower surface of the semiconductor layer 43, and a gate electrode 44 is provided on the gate insulating film 46.

A superconducting FET has a superconducting source electrode 4 due to the superconducting proximity effect.
1 and the superconducting current flowing through the semiconductor layer 43 between the superconducting drain electrode 42 by controlling the superconducting current with a gate voltage;
It is a high-speed operating element.

Furthermore, a three-terminal superconducting element has been announced in which a channel is formed between a source electrode and a drain electrode using a superconductor, and the current flowing through this superconducting channel is controlled by a voltage applied to a gate electrode.

Problems to be Solved by the Invention The above-described superconducting base transistor and superconducting FET both have a portion in which a semiconductor layer and a superconductor layer are laminated. However, it is difficult to fabricate a stacked structure of a semiconductor layer and a superconductor layer using oxide superconductors, which have been studied in recent years. Moreover, even if this structure could be fabricated, it was difficult to control the interface between the semiconductor layer and the superconductor layer, and the device did not operate satisfactorily.

Furthermore, in order to utilize the superconducting proximity effect, the superconducting FET has a superconducting source electrode 41 and a superconducting drain electrode 42.
must be made close to each other within several times the coherence length of the superconductor that constitutes each. In particular, an oxide superconductor has a short coherence length, so when an oxide superconductor is used, the distance between the superconducting source electrode 41 and the superconducting drain electrode 42 must be several IQ nm or less. Such microfabrication is extremely difficult, and conventionally superconducting F using oxide superconductors
ET could not be produced with good reproducibility.

Furthermore, superconducting devices with conventional superconducting channels are
Although modulation operation was confirmed, complete on/off operation was not possible due to the high carrier density. Since oxide superconductors have a low carrier density, it is expected that by using them for superconducting channels, it will be possible to realize the above-mentioned devices that perform perfect on/off operation. However, the thickness of the superconducting channel must be approximately 5r+m, and it has been difficult to realize such a configuration.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a superconducting element having a novel configuration and a method for manufacturing the same, which solves the problems of the prior art described above.

Means for Solving the Problems According to the present invention, there are provided a superconducting channel formed in an oxide superconducting thin film formed on a substrate, and source electrodes disposed near both ends of the superconducting channel to flow current through the superconducting channel. and a superconducting element comprising a drain electrode and a gate electrode disposed on the superconducting channel to control current flowing through the superconducting channel, in which component elements of the substrate diffuse into the oxide superconducting thin film to achieve superconductivity. A superconducting device is provided, characterized in that a missing non-superconducting region is formed and the thin superconducting channel is provided on the non-superconducting region of the oxide superconducting thin film.

Further, in the present invention, an oxide superconducting thin film is formed on a substrate, and energy is locally applied to a part of the oxide superconducting thin film to diffuse component elements of the substrate to form the non-superconducting region. A method for manufacturing a superconducting element is provided, the method comprising the steps of:

- Surrogate The superconducting element of the present invention includes a superconducting channel made of an oxide superconductor, a source electrode and a drain electrode that allow current to flow through the superconducting channel, and a gate electrode that controls the current flowing through the superconducting channel. In the superconducting element of the present invention, each electrode does not necessarily have to be a superconducting electrode.

Furthermore, while conventional superconducting FETs use the superconducting proximity effect to cause a superconducting current to flow through the semiconductor, in the superconducting element of the present invention, the main current flows through the superconductor. Therefore, restrictions on microfabrication techniques required when manufacturing conventional superconducting FETs are relaxed.

The superconducting channel must have a thickness of the order of 5r+m in the direction of the electric field generated by the gate electrode in order to be opened and closed by the voltage applied to the gate electrode. The main focus of the present invention is to realize such an ultra-thin superconducting channel. In the superconducting element of the present invention, a non-superconducting region is formed in the oxide superconducting thin film by the substrate components diffused into the oxide superconducting thin film, and the superconducting portion thinned by the non-superconducting region is used as a superconducting channel.

In the superconducting element of the present invention, the above-mentioned non-superconducting region allows
Forms ultra-thin superconducting channels. Therefore, this non-superconducting region must be formed in a portion of the oxide superconducting thin film underlying the superconducting channel portion of the superconducting element. Therefore, in the method of the present invention, energy is locally applied to the portion of the oxide superconducting thin film that will become the superconducting channel using, for example, a focused ion beam, laser, etc., thereby diffusing the constituent elements of the underlying substrate.

In the superconducting element of the present invention, the substrate includes MgO, 5r
An oxide single crystal substrate such as TiO3 can be used.

These substrates are preferable because it is possible to grow an oxide superconducting thin film made of highly oriented crystals. Furthermore, a semiconductor substrate having an insulating layer on its surface can also be used.

Further, the superconducting element of the present invention includes Y-Ba-CuO
Any oxide superconductor can be used, such as a Bi-3r-Ca-Cu-''O-based oxide superconductor, a TI-Ba-Ca-Cu-0-based oxide superconductor, and the like.

EXAMPLES Hereinafter, the present invention will be explained 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.

Example FIG. 1 shows a cross-sectional view of the superconducting element of the present invention.

The superconducting element shown in FIG. 1 has an oxide superconducting thin film 1 formed on a substrate 5 and having a non-superconducting region 50 in which substrate components have diffused and lost superconductivity. Oxide superconducting thin film 1
The upper part of the non-superconducting region 50 is an extremely thin superconducting channel 10 with a thickness of about 5 nm. Superconducting channel 1
A gate electrode 4 is arranged on the oxide superconducting thin film 1, and a source electrode 2 and a drain electrode 3 are arranged on both sides of the superconducting channel 10 on the oxide superconducting thin film 1.

Referring to FIG. 2, the procedure for manufacturing the superconducting element of the present invention using the method of the present invention will be described. First, an oxide superconducting thin film 1 as shown in FIG. 2(a) is deposited on a substrate 5 as shown in FIG. to form. The thickness of the oxide superconducting thin film 1 is preferably 200 to 300 nm, and the oxide superconductor is a Y-Ba-Cu-0 based oxide superconductor or a B1-5r-Ca-Cu-0 based oxide superconductor. , TI-Ba-Ca-Cu-0 based oxide superconductors are preferred, and a C-axis oriented thin film is preferred. This is because the C-axis oriented oxide superconducting thin film has a large critical current density in the direction parallel to the substrate. The substrate 5 may be an insulating substrate such as a Mg0 (100) substrate or a SrT+03 (100) substrate, or a surface coated with, for example, MgAl2O4.
A semiconductor substrate made of Si or the like having an insulating film laminated with BaTiO2 and BaTiO2 is preferable.

Next, as shown in FIG. 1(C), the oxide superconducting thin film 1 is locally irradiated with a laser beam or a focused ion beam as shown by the arrow to remove the constituent elements of the substrate 5 from the oxide superconducting thin film 1.
to form a non-superconducting region 50. A portion of the oxide superconducting thin film 1 above the non-superconducting region 50 becomes a superconducting channel 10.

When forming the non-superconducting region 50 by irradiating a laser beam, the laser is preferably a high-power laser such as an excimer laser, a carbon dioxide laser, or a YAG laser. for example,
When using an Ar radar with a wavelength of 514 r++++,
The irradiation output is 2. It is preferable to use OW and scan at 100 μm/sec. On the other hand, when forming the non-superconducting region 50 by irradiating a focused ion beam, the irradiated ions are preferably Ar ions, the beam diameter is preferably 0.2 μm or less, and the acceleration voltage is preferably 50 kV or less.

Next, a gate electrode is fabricated on the superconducting channel 10.

The gate electrode preferably has a structure in which a metal layer is laminated on an insulator layer. Therefore, an insulating film 6 and a metal film 7 are laminated on the oxide superconducting thin film 1 as shown in FIG. 2(d). It is preferable to use an insulator such as MgO that does not create a large level at the interface with the oxide superconducting thin film for the insulating film 6, and the thickness thereof is set to 10 nm or more. Further, it is preferable to use a high melting point metal such as Au or T11W, or a silicide thereof for the metal film 7. The stacked films are removed by etching leaving only the portion above the superconducting channel 10, as shown in FIG. 2(e), to form the gate electrode 4.

Finally, as shown in FIG.
Then, a drain electrode 3 is formed to complete the superconducting element of the present invention.

When the superconducting element of the present invention is manufactured by the method of the present invention, restrictions on microfabrication techniques required when manufacturing a superconducting FET are relaxed. Furthermore, since the surface can be made flat, it becomes easier to form wiring later as required. Therefore,
It is easy to manufacture, has stable device performance, and has good reproducibility.

As described in detail, the superconducting element of the present invention has a configuration in which the superconducting current flowing in the superconducting channel is controlled by the gate voltage. Therefore, like the conventional superconducting FET,
Since the superconducting proximity effect is not used, microfabrication technology is relaxed. Furthermore, since there is no need to stack a superconductor and a semiconductor, high-performance devices can be manufactured using oxide superconductors.

The present invention further promotes the application of superconducting technology to electronic devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the superconducting device of the present invention, FIG. 2 is a schematic diagram showing the steps for producing the superconducting device of the present invention by the method of the present invention, and FIG. 3 is a schematic diagram of the superconducting device of the present invention. FIG. 4 is a schematic diagram of a base transistor; FIG. 4 is a schematic diagram of a superconducting FET. [Main reference numbers] 1... Oxide superconducting thin film, 2... Source electrode, 3... Drain electrode, 4... Gate electrode, 5... Substrate patent applicant Sumitomo Electric Industries, Ltd.

Claims (2)

[Claims] (1) A superconducting channel formed in an oxide superconducting thin film formed on a substrate, a source electrode and a drain electrode arranged near both ends of the superconducting channel to flow a current through the superconducting channel, and a source electrode and a drain electrode arranged on the superconducting channel. In a superconducting element comprising a gate electrode disposed in a gate electrode for controlling a current flowing through the superconducting channel, a non-superconducting region is formed in which component elements of the substrate diffuse into the oxide superconducting thin film and lose superconductivity; A superconducting element, characterized in that the thin superconducting channel is provided on the non-superconducting region of the oxide superconducting thin film. (2) In the method for producing a superconducting element according to claim 1, an oxide superconducting thin film is formed on a substrate, and energy is locally applied to a part of the oxide superconducting thin film to obtain the constituent elements of the substrate. A method for manufacturing a superconducting element, the method comprising the step of diffusing the non-superconducting region to form the non-superconducting region.