JPH01779A - Superconducting transistor and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a superconducting transistor that utilizes an insulator-semiconductor-superconductor phase transition and a method for manufacturing the same.

(Prior Art) Until now, the development of ultra-high-density electronic devices and ultra-high-speed electronic devices has focused on silicon and compound semiconductors. High density and high speed conventional semiconductor devices have been achieved through advanced microfabrication technology, homogeneous and highly perfect crystal manufacturing technology, and device design technology using simulation.

Heat generation is an issue that will become increasingly important in the future as the density and speed of semiconductor devices are further increased. This is considered to be a major factor that limits the ability to increase the density and speed of semiconductor devices, in addition to crystal perfection and microfabrication technology.

Superconducting devices, such as Josephson junction devices, are superior to semiconductor devices in terms of heat generation. However, to date, there is no prospect of full-scale practical use of superconducting devices. The reasons for this are that superconductivity can only be achieved at extremely low temperatures, such as the temperature of liquid helium, that metals or intermetallic compounds are used as superconducting materials and are easily oxidized, and that they are used as insulating films in Josephson junction devices. They do not have the temporal stability and spatial properties of metal oxides, and are difficult to use because they are essentially two-terminal devices.

In recent years, superconducting transistors combining superconductors and semiconductors have been prototyped to overcome the shortcomings of Josephson junction devices, which are two-terminal devices.

In this method, a pair of superconductor electrodes (source and drain electrodes) are provided on one surface of the semiconductor layer, facing each other with a small distance, and an electrode (gate electrode) that controls the carrier concentration distribution within the semiconductor layer is provided on the other surface. It has a built-in structure. If a bias is applied by the gate electrode in a direction that decreases the carrier concentration near the source and drain, a Josephson junction will not be formed between the source and drain electrodes, and no superconducting current will flow between the source and drain electrodes. This is the off state of the transistor. On the other hand, if a bias is applied to increase the carrier concentration near the source and drain using the gate electrode, the source will increase above a certain voltage.

A Josephson junction (superconducting junction) is formed between the drain electrodes, and the transistor is turned on. In this method, a pair of superconducting electrodes of a Josephson element, which were conventionally opposed in the thickness direction, are expanded on a plane, and it is possible to form a superconducting junction by controlling the carrier concentration between the superconducting electrodes. It can be said that it is controlled. Since current flows through the superconducting junction with zero voltage, this superconducting transistor theoretically does not generate heat.

This superconducting transistor has the advantage of being easier to use than conventional Josephson devices in that it is a three-terminal element, but its operating temperature is extremely low, at or near liquid helium, and the superconducting electrode is Unless the drawback of superconductor devices, which is their instability in air, is resolved, it will be difficult to put them into practical use.

(Problems to be Solved by the Invention) As described above, superconducting devices are attracting attention as they do not generate heat and can exceed the limits of high density and high speed of conventional semiconductor devices, but mainly due to their material properties. It has not been put into practical use due to restrictions.

The present invention has been made in view of these points, and it is an object of the present invention to provide a superconducting transistor that has a new operating principle, can operate at temperatures higher than liquid nitrogen temperature, and has excellent stability in air. purpose.

A further object of the present invention is to provide a method for manufacturing a superconducting transistor based on such a new principle.

[Structure of the Invention (Means for Solving Problems)] A superconducting transistor according to the present invention uses an oxide film having a channel layer in which a superconductor-semiconductor-insulator phase transition occurs by carrier concentration control at high temperatures. , is characterized in that it is provided with a source, a drain electrode, and a gate electrode for controlling the carrier concentration of the channel layer. The specific structures include one in which the gate electrode part has a MrS structure or a Schottky gate structure and the carrier concentration in the channel layer is controlled by electric field effect, and the other in which the carrier concentration in the channel layer is controlled by carrier injection from the gate electrode. There is. Further, as operating modes, there are two possible operating modes: a normally-on type in which the channel layer is a superconductor when the gate voltage is zero, and a normally-off type in which the channel layer is a high-resistance insulator or semiconductor when the gate voltage is zero. Furthermore, there are structures in which the source, drain and gate electrodes are formed on different sides of the oxide film including the channel layer, and structures in which they are all formed on the same side.

In the following explanation, a film that is in a superconducting state when no gate voltage is applied is referred to as an "oxide superconductor film," and it becomes a superconducting state by applying a gate voltage and controlling the carrier concentration. This film is called an "oxide semiconductor film."

The method of the present invention is characterized in that, in manufacturing such a superconducting transistor, an oxide film including a channel layer is formed by sputtering.

Many oxide superconductors are known, but
The oxide film material used for the channel layer in the present invention is:
A perovskite-type oxide containing a rare earth element with a high critical temperature is preferred. Contains the rare earth elements mentioned here. It is sufficient that the oxide having a babeskite structure can realize a superconducting state, and A Ba 2 Cu with oxygen defects can be used.
30t-a system (A is Y, Yb, Ho, Dy, Eu, E
r, Tll1. The oxide has a perovskite structure in a broad sense, such as a defective perovskite type such as a rare earth element such as Lu, or a layered perovskite type such as a 5r-La-Cu-0 system. Rare earth elements are also broadly defined to include Sc, Y, and lanthanum elements. As a representative system, Y
In addition to -Ba-Cu-0, Y is Yb.

Ho * D y + E u + E r +
Systems substituted with rare earth elements such as T m and Lu, Sc
Examples include -Ba-Cu-0 series, 5r-La-Cu-0 series, and systems in which Sr is replaced with Ba or Ca. Small deviations from the stoichiometric composition of these materials are tolerated. These oxides can also behave as normal semiconductors depending on their composition. For example, La 2 Cu
04 is known as a high resistance p-type semiconductor. When a predetermined voltage is applied to this, the portion with high carrier density behaves as a superconductor due to a change in carrier density distribution.

(Function) By selecting the composition, the above-mentioned oxide can have a very high critical temperature Tc exhibiting superconductivity of 30 or more, and exhibit superconductivity even at liquid nitrogen temperature by controlling the carrier concentration. With advances in material production technology, there is a strong possibility that materials with even higher critical temperatures will be obtained.

These oxide films also have superior stability in the atmosphere compared to conventional metal or intermetallic superconductors.

It also has excellent interfacial properties with semiconductors such as silicon, and the superconducting transistor of the present invention can be formed using such a semiconductor substrate.

In the device of the present invention, the channel layer behaves as a superconductor in the on state, so that the source 1.・Current flows between the rain electrodes without voltage drop. In particular, if an oxide superconductor is used for the source and drain electrodes as well as the channel layer, current can be passed through the source and drain electrodes without generating heat.

As described above, the present invention has a new operating principle,
It can operate at temperatures that can be obtained with a simple refrigerator, and stable device characteristics with little change over time can be obtained. Moreover, since it is a three-terminal device, it is easy to use and does not generate heat, making it possible to realize ultra-high density integrated circuits and ultra-high speed devices that cannot be obtained with devices using only conventional semiconductor materials.

Further, according to the method of the present invention, a superconducting transistor having the above-mentioned excellent performance can be obtained using a simple film forming technique called sputtering.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows one embodiment of a superconducting transistor. Board 1
is a p-type Si substrate doped with boron at 1019/cm'. A silicon oxide film 2 of about 100 layers is formed on the surface of the substrate 1 by thermal oxidation. An oxide semiconductor film 3 is formed on the oxide film 2 of the substrate 1 by sputtering, which causes a superconductor-semiconductor-insulator phase transition by controlling carrier concentration. On this oxide semiconductor film 3,
Source and drain electrodes 4 and 5 are formed at predetermined intervals. The source and drain electrodes 4.5 are main electrodes 41 made of oxide superconductor films formed at predetermined intervals.
+51, and terminal electrodes 42 and 52 formed of metal films on these main electrodes 41 and 51, respectively. A gate electrode 6 is formed on the back surface of the substrate 1.

To explain the specific manufacturing method of the device of this example, as the oxide semiconductor film 3, CLao, e, Sro, os) 2 CuO4 is formed to a thickness of 1000 nm by sputtering, and the source and drain layers are The oxide superconducting film of the main electrode 41.5□ is (Lao, s, S ro, +s ) 2 Cu 0
3.9 was similarly deposited by sputtering and patterned. The distance between these main electrodes 4.5 is 0.2μ
It is m. Terminal electrodes 4□, 52 made of an Au film are formed on the source and drain main electrodes 41.degree. 51, and a gate electrode 6 is also formed of an Au film on the back surface of the substrate 1.

This element uses the surface portion of the oxide semiconductor film 3 as a channel layer, and by controlling the carrier strength of the channel layer with the gate electrode 6, this channel layer portion is formed between a high-resistance semiconductor and a superconductor. It is a normally-off transistor whose operating principle is phase transition. now,
Zero voltage is applied to the gate electrode 6 or the carrier density near the surface (
In this embodiment, when a negative bias voltage is applied that reduces the hole density, the source and drain electrodes 4.
The oxide semiconductor film 3 between the transistors 5 and 5 exhibits high resistance, and the transistor is kept in an off state. When the gate electrode 6 is positively biased, contrary to the above, holes are collected on the surface of the oxide semiconductor film 3 and the hole density increases. behaves as a superconductor. In other words, the channel layer becomes a superconductor state and becomes a source.

A current flows between the drain electrodes 4.5 without a voltage drop. This is the on state of the transistor.

A in FIG. 3 shows the gate voltage dependence of the superconducting critical current between the source and drain of the superconducting transistor of this example. A rapid increase in superconducting critical current is observed at a gate voltage of 500 mV. The measurement temperature is 20°C.

FIG. 2 shows a superconducting transistor according to another embodiment. The element of this example differs from that in FIG. 1 in that the oxide semiconductor film 3 in FIG. 1 has a stacked structure of a p-type St film 7 and the oxide semiconductor film 3. Other parts corresponding to those in FIG. 1 are designated by the same reference numerals as in FIG. 1, and detailed description thereof will be omitted. The p-type Si film 7 has a thickness of, for example, 500, and the oxide semiconductor film 3 has a thickness of, for example, 100, using the same materials and manufacturing method as in the previous embodiment.
Assume 0 people.

The superconducting transistor of this embodiment basically operates in the same way as the previous embodiment. In this example, p-type S
The t film 7 serves as a carrier supply source, and when a positive voltage is applied to the gate electrode 6, a large amount of holes are supplied from the p-type Si film 7 to the oxide semiconductor film 3. Therefore, the superconducting critical current flows at a lower gate voltage than in the previous embodiment. The situation is shown in the third part.
It is shown by curve B in the figure. A superconducting critical current rapidly flows at a gate voltage of about 200 mV.

The present invention can be further modified in various ways by combining the structure of the gate electrode portion, the carrier concentration control method of the channel layer, the operation mode, etc. Examples of these will be described below. In the following embodiments, parts corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

The film forming conditions for each part are also the same as in the previous example unless otherwise explained.

FIG. 4 shows an example of a MOS type superconducting transistor in which the gate electrode is formed on the same side as the source and drain electrodes. In contrast to FIGS. 1 and 2, the gate electrode 6 is formed on the back surface of the substrate 1, whereas in this embodiment, the oxide semiconductor film 3 is formed, and the main electrodes 4 for source and drain are formed. ．． 51
After forming, a gate electrode 6 is formed on the channel layer portion of the surface of the oxide semiconductor film 3 with a gate insulating film 6 interposed therebetween.

If the material composition and manufacturing conditions of the oxide semiconductor film 3 are the same as in the previous embodiment, this transistor is normally off. When a negative voltage is applied to the gate electrode 6, the hole concentration in the surface channel layer portion of the oxide semiconductor film 3 increases, and this channel layer portion becomes a superconductor state at a predetermined voltage or higher.

This is on. In FIG. 4, it is effective to provide a p-type Si layer serving as a hole supply source under the oxide semiconductor film 3 as in FIG. 2.

The embodiment shown in FIG. 5 differs from that in FIG. 4 in the structure of the gate electrode 6 portion. In contrast to the MOS structure shown in FIG. 4, this example has a structure in which the gate electrode 6 is brought into direct contact with the oxide semiconductor film 3 and holes can be injected from the gate electrode 6 into the oxide semiconductor film 3. . In order to efficiently inject holes into the oxide semiconductor film 3 from the gate electrode 6, it is preferable to use a metal such as Au, Ag, Cr, or Nl as the gate electrode 6.

This superconducting transistor is also of the normally-off type, as in each of the previous embodiments. When the hole concentration in the channel layer is increased by applying a positive voltage to the gate electrode 6 and injecting holes into the oxide semiconductor film 3, this portion transitions to a superconductor state and turns on.

In the examples so far, a relatively thick oxide semiconductor film formed by a sputtering method is used as it is, and a transistor is constructed in which the surface portion thereof serves as a channel layer. Next, an example will be described in which, after forming an oxide film, ions are implanted into the surface portion that will become the channel layer, so that the composition and characteristics of the channel layer portion and the portions below it are made different.

In the embodiment shown in FIG. 6, an oxide superconductor film 8 which becomes a built-in superconductor is formed on the oxide film 3 shown in FIG. A high resistance layer 9 that is a semiconductor or an insulator is formed. Specifically, the oxide superconductor film 8 is, for example, a high temperature superconductor (Lao, 85Sro, +5) 2 Cu o
A 4-y film is formed by sputtering, and A, 1
A high resistance layer 9 is formed by implanting 1' ions. This high-resistance layer 9 causes a phase transition between a high-resistance material and a superconductor by controlling the carrier concentration. In addition to AI ion, B.

Cations such as Mg, Be, Ca, etc. can be used.

In the superconducting transistor of this example, only the surface part of the oxide superconductor film is made into a semiconductor or insulator by ion implantation, and the part below it is made into a superconducting state.The operating principle is as shown in FIG. Same as example.

The elements shown in FIGS. 7 and 8 are based on the same idea and are modified examples of the structures shown in FIGS. 4 and 5, respectively. As described above, a normally-off type device can be obtained by forming a high resistance layer by ion implantation on the surface of an oxide superconductor film, which is a superconductor in the steady state, and using it as a channel layer. . Conversely, if we form an oxide semiconductor film, which is a semiconductor or insulator with high resistance in its steady state, and form a superconductor by implanting negative ions such as oxygen into its surface, we can create a normally-on device. Obtainable.

In the above, a relatively thick oxide film is formed by sputtering, and the surface portion thereof is used as a channel layer. can be taken as a thing. Such an embodiment will now be described.

FIG. 9 shows a superconducting transistor of such an embodiment. For example, a 50-layer oxide superconductor film 10 is formed on a substrate 1 on which an oxide film 2 is formed, and a high-resistance layer 11 is formed by implanting positive ions into a portion to be used as a channel layer. As described in the previous embodiments, the oxide superconductor film 10 has, for example, CLao, s, Sro, +, )
2Cu 0a-y film, and the high resistance layer 11 portion is formed by ion implantation of A. In this case, high resistance layer 1
The oxide superconductor films 10 left on both sides of the electrode 1 function as the source and drain main electrodes 41+51 in each of the previous embodiments. Therefore, there is a metal terminal electrode 42 directly on top of these.
+52 is formed. Gate electrode 6 is formed directly on high resistance layer 11. The gate electrode 6 is the fifth
It is formed of, for example, an Au film, as shown in FIGS.
Holes can be injected into the high resistance layer 11.

This superconducting transistor is also of the normally-off type, like the ones shown in FIGS. 5 and 8. By applying a positive voltage to the gate electrode 6 and injecting holes into the high resistance layer 11, this portion can undergo a phase transition to a superconductor, thereby turning on the device.

C in FIG. 11 shows the gate voltage dependence of the source-drain resistance of the device of this example. Gate voltage V as shown. At a certain value (1.4 V in the case of the figure), a phenomenon of sudden resistance value is observed.

The resistance when off is approximately 2Ω. The measurement temperature is 20°C.

FIG. 10 is a modification of FIG. 9. In this embodiment, as in the case of FIG. 9, a thin oxide superconductor film is formed by sputtering, and then patterned by photolithography to separately form source and drain main electrodes 4z and 5+. After this, a high resistance layer 11 is deposited by sputtering on a portion that will become a channel region. The portions that will become the source and drain main electrodes 41°5 are made of the same oxide superconductor film as in the previous embodiment, for example (Lao, g, Sro, +5
)2CuO4-y film, and the high-resistance layer 11 serving as a channel layer is an oxide semiconductor film, for example, a (Lao, s Sro, o2)2Cu04-y film.

The operating principle of the superconducting transistor of this embodiment is the same as that of the previous embodiment. In the case of this embodiment, the source-to-drain resistance during off-state can be made higher than in the previous embodiment shown in FIG. D shown in FIG. 11 is an example of the characteristic. The threshold voltage has increased to about 2.4V, but the resistance when off has also increased to 4.7Ω.

In the embodiments shown in FIGS. 9 and 10, the source, drain electrode, and gate electrode were formed on one surface of the oxide film serving as the channel layer, but the source, drain electrode, and gate electrode may be formed on different surfaces. is possible. Such an embodiment will now be described.

FIG. 12 shows an embodiment that is a modification of the embodiment shown in FIG. 9, in which a gate electrode 6 is first formed on a substrate 1 on which an oxide film 2 is formed, and an oxide superconductor film 10 is applied thereon by sputtering. The high resistance layer 11 is formed by ion implantation into the channel layer portion.
It was converted into . The operating principle is the same as that shown in FIG. 9, except that the manufacturing process is different. Therefore the 9th
The same normally-off characteristics as shown in the figure can be obtained.

FIG. 13 is a modification of FIG. 10, in which the gate electrode 6 is formed on the substrate before the oxide superconductor film is formed. The superconducting transistor of this embodiment also has characteristics similar to those shown in FIG. 10.

In the embodiments shown in FIGS. 9 to 13, the gate electrode was used as a carrier injection electrode, but a similar thin oxide film was used to transform the gate electrode into MO as described below.
It can have three structures.

In the embodiment shown in FIG. 14, a gate insulating film 7 is interposed between the gate electrode 6 and the high resistance layer 11 in the structure shown in FIG. The device of this embodiment is a normally-off type, and by applying a negative voltage to the gate electrode 6, a positive voltage is applied to the high resistance layer 11 under the gate electrode 6 from the oxide superconductor film 10 on both sides. The pores are collected, and the high resistance layer 11 becomes a superconductor state, that is, an on state, when the gate voltage exceeds a certain level.

The embodiment shown in FIG. 15 is similar to the structure shown in FIG. 10 in which a gate insulating film 7 is interposed between the gate electrode 6 and the high resistance layer 11. The device of this embodiment operates similarly to the device of the previous embodiment.

According to the present invention, a normally-on transistor can be constructed using a thin oxide superconductor film. Such embodiments are described below.

FIG. 16 shows an example of this, in which an oxide superconductor film 12 is formed by sputtering on a substrate 1 on which an oxide film 2 is formed, and a gate electrode 6 and source and drain electrodes 42r42 are formed thereon. . Here, source and drain electrodes 42 and 52
A material that makes ohmic contact with the oxide superconductor film 12 is selected for the gate electrode 6, and a material that forms a barrier similar to a Schottky gate structure is selected for the gate electrode 6.

In the device of this example, the gate voltage is zero and the source voltage is zero.

The drains are short-circuited by the oxide superconductor film 12 and are on. When a positive voltage is applied to the gate electrode 6,
Holes in the channel layer under the gate electrode 6 are removed by the electric field, and the channel layer becomes depleted at a predetermined voltage or higher, becoming a high-resistance semiconductor or insulator. That is, the element is turned off.

E in FIG. 18 is an example of the characteristic. The resistance between the source and the drain increases at a threshold voltage of 1.2V, and becomes 1.6Ω in the off state. The measurement temperature is 20°C.

FIG. 17 shows the gate electrode 6 in the embodiment of FIG.
This is an example in which a thin n-type St film 13 of about 50 layers is interposed between the oxide superconductor film 12 and the oxide superconductor film 12. The device of this embodiment basically operates in the same way as the device shown in FIG. 16 above.

In this embodiment, when a negative voltage is applied to the gate electrode 6, holes in the oxide superconductor film 12 under the gate electrode 6 are sucked out to the n-type St film 13, and as a result, the oxide film in the channel region resistance increases. That is, as in the previous embodiment, it is normally on, but it is turned on by applying a voltage of opposite polarity to the gate electrode. The characteristics of the device of this example are shown in FIG. 18F. In the case of this embodiment, the gate voltage vG is shown in absolute value in FIG. Although the threshold voltage is higher than in the previous example,
Off resistance is also high.

FIG. 19 shows the gate electrode 6 in the embodiment of FIG.
A gate insulating film 7 is interposed between the oxide superconductor film 12 and the oxide superconductor film 12, so that the gate portion has an MO3 structure. The device in this embodiment is also normally on. and gate electrode 6
By applying a positive voltage to and removing holes from the channel layer portion under the gate electrode 6, the channel layer can be made into a high resistance layer and the device can be turned off.

In FIGS. 16, 17, and 19, the thin oxide superconductor film itself is used as the channel layer, and the source, drain, and gate electrodes are formed on the negative side of the channel layer.
It constitutes an on-type transistor. It is also possible to have a structure basically similar to these, but to form the gate electrode, source, and drain electrodes on different surfaces of the oxide superconductor film.

For example, in FIG. 20, the gate voltage +56 in FIG.
This is an example in which the oxide superconductor film 12 is formed under the oxide superconductor film 12.

In the present invention, it is further possible to use an oxide magnetic film or an oxide film showing a magnetic material-non-columnar transition as a carrier supply source for an oxide film showing a superconductor-semiconductor-insulator phase transition. can.

The superconducting critical temperature of the oxide film exhibiting high temperature superconductivity used in the present invention is greatly lowered by the influence of iron group ions such as Cr, Mn, and Ni, so such characteristics are utilized. Such embodiments are described below.

FIG. 21 shows a superconducting transistor of one embodiment.

An oxide film 2 is formed on the substrate 1. First, an oxide magnetic film 1 is formed on the substrate 1.
4 is formed by a sputtering method, and an oxide superconductor film 15 is laminated thereon as a channel layer by a sputtering method. Specifically, the oxide magnetic film 14 has, for example, Lao of about 5OA, 9Sro, +Mn
It is an O3 film. The oxide superconductor film 15 on this is an oxide film exhibiting high-temperature superconductivity, such as (Lao, a, S
ro, +q ) 2 Cu 04 film. On the oxide superconductor film 15, there are source and drain main electrodes 4 made of an oxide superconductor film with an interval of about 0.5 μm, for example.
+, 5z are formed, and a gate insulating film 7 is formed on the channel region.
A gate electrode 6 is formed through the gate electrode 6.

The device of this embodiment is of a normally-on type because the channel layer, that is, the oxide superconductor film 15 is in a superconductor state when the gate voltage is zero. When a negative voltage is applied to the gate electrode 6, holes are transferred from the oxide magnetic film 14 to the oxide superconductor film 15.
However, these holes also have the properties of magnetic ions. As a result, the critical temperature of the oxide superconductor film 15 in the superconductor state decreases, and the film transitions to a normal conductor at the operating temperature. This creates a resistance between the source and drain,
The transistor is turned off.

G in FIG. 23 shows the gate voltage dependence of the superconducting critical current between the source and drain of this device.

In this figure, the gate voltage is shown as an absolute value, and it is observed that the current suddenly decreases when the gate voltage reaches -50 mV. The measurement temperature is 20°C.

The superconducting transistor of this example can be turned off even if a positive voltage is applied to the gate electrode. That is, when a positive voltage is applied to the gate electrode 6, the hole concentration in the channel region below it decreases, resulting in a high resistance l;.

FIG. 22 shows a modification of FIG. 21, in which a gate electrode 6 is formed on the back surface of the substrate 1. In the structure of this example,
By applying a positive voltage to the gate electrode 6, holes are injected from the oxide magnetic film 14 into the oxide superconductor film 14, and the device is turned off on the same principle as the device of the previous embodiment.

FIG. 24 shows the oxide magnetic film 1 only under the gate electrode 6.
4 was formed. The device of this example can also be turned off by applying a positive voltage to the gate electrode 6 and injecting holes from the oxide magnetic film 14 into the oxide superconductor film 15 which is the channel layer. .

In these examples, any one of a paramagnetic material, a ferromagnetic material, and a diamagnetic material can be used as the magnetic oxide. It is also possible to use a chalcogenide compound magnetic material instead of an oxide. In the embodiment shown in FIG. 21, the oxide magnetic film 14 is Tl doped with 0.1% vanadium.
The characteristics when an O2 film is used are shown in H in FIG.

In the embodiments of FIGS. 21, 22 and 24,
It is also effective to use, as the oxide magnetic film 14, an oxide film that causes a nonmagnetic-magnetic phase transition. When such a material is used, when a bias is applied to the gate electrode and holes are injected from the non-magnetic oxide film into the oxide film of the channel layer, the critical temperature of the channel layer increases as in the previous example. decreases.

At the same time, the nonmagnetic oxide film becomes magnetic, and the superconducting critical temperature of the channel layer further decreases due to the proximity effect. Therefore, depending on the gate voltage, the transistor is turned on and
Off control is effectively performed.

The present invention is not limited to the above embodiments, and can be implemented with various modifications. For example, in each of the above embodiments, a metal electrode was used for the gate electrode, but the source,
An oxide superconductor can be used similarly to the drain main electrode. In this way, when the element of the present invention is incorporated into a concrete circuit, it is possible to prevent the gate electrode wiring from becoming long and generating heat there, which is advantageous in practice. Further, in the embodiment, an oxide superconductor film was used for the main electrodes of the source and drain, but the present invention is also effective when these are composed of only metal electrodes. The oxide film material used in the present invention that exhibits a superconductor-semiconductor-insulator phase transition by carrier concentration control may be a perovskite-type oxide containing a rare earth element with a high critical temperature as described above. .

Further, in the embodiment, a Si substrate was exclusively used as the substrate, but it is also possible to use other semiconductor substrates, dielectric substrates, or metal substrates. In particular, in order for the high-temperature superconductor to exhibit high-temperature superconductivity characteristics, it is preferable to select a material whose oxide film and substrate have the same coefficient of thermal expansion.

[Effects of the Invention] As described above, according to the present invention, an oxide film that exhibits a superconductor-semiconductor-insulator phase transition at high temperatures is used in the channel layer portion, and the field effect or carrier injection by the gate electrode is suppressed. to control the carrier concentration in the channel layer,
As a result, a new superconducting transistor that performs on/off control can be obtained. If this transistor is used, it will be possible to construct excellent electronic circuits that, in principle, do not generate heat by taking advantage of its superconducting properties at liquid nitrogen temperatures or higher temperatures.

Further, according to the method of the present invention, a superconducting transistor based on such a new principle can be easily manufactured by using a simple film forming technique called sputtering and, if necessary, also using ion implantation technique.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a normally-off superconducting transistor using a relatively thick oxide semiconductor film, and FIG.
The figure shows a modified example, Figure 3 shows the characteristics of these superconducting transistors, and Figure 4 shows a normally-off superconductor example using a similar oxide semiconductor film and MO3 structure gate. Figure 5 shows a normally-off type superconducting transistor using the same charge injection type gate electrode structure, and Figure 6 shows a channel layer formed on the surface of an oxide superconductor by ion implantation. FIG. 7 is a diagram showing a normally-off superconducting transistor of the formed example, FIG. 7 is a diagram showing a normally-off superconducting transistor with a MOS gate structure using a similar channel layer, and FIG. 8 is also a charge injection type superconducting transistor. Figure 9 shows a normally-off superconducting transistor using a gate electrode; FIG. 9 shows a normally-off superconducting transistor using a thin oxide semiconductor film and a charge injection gate electrode. , FIG. 10 is a diagram showing a modification thereof, FIG. 11 is a diagram showing the characteristics of the superconducting transistor shown in FIGS. 9 and 10, and FIG.
The figure shows a superconducting transistor according to an example in which the gate electrode is placed under an oxide semiconductor film, and FIG. 13 is a diagram showing an embodiment of the superconducting transistor shown in FIG. FIG. 14 is a diagram showing an example superconducting transistor in which the superconducting transistor in FIG. 9 is a MOS type, and FIG.
FIG. 16 shows a normally-on type superconducting transistor using a thin oxide superconductor film, and FIG. 17 shows a modified example of the OS type superconducting transistor. Figure 18 shows the characteristics of the superconducting transistor shown in Figures 16 and 17. Figure 19 shows the superconducting transistor of the MO'S type superconducting transistor shown in Figure 16. 20 is a diagram showing a superconducting transistor according to an embodiment in which the gate electrode of FIG. 16 is placed under an oxide superconductor film, and FIG. 21 is a diagram showing a superconducting transistor using an oxide magnetic film as a carrier supply source. 22 is a diagram showing a modified example thereof, FIG. 23 is a diagram showing the characteristics of the superconducting transistor according to the embodiment of FIG. 21, and FIG. FIG. 2 is a diagram showing a superconducting transistor according to an example in which an oxide magnetic film is used as a carrier supply source in a gate electrode portion. DESCRIPTION OF SYMBOLS 1... P-type Si substrate, 2... Oxide film, 3... Oxide semiconductor film (superconductor-semiconductor-insulator 4... Source electrode, 5... Drain electrode, 41+51...・Lord 15
Pole (oxide superconductor film), 42 + 52... terminal electrode, 6... gate electrode, 3o... p-type Si film,
7... Gate insulating film, 8... Oxide superconductor film, 9
... High resistance layer (ion implantation layer), 10 ... Oxide superconductor film, 11 ... High resistance layer, 12 ... Oxide superconductor film,] 3 ... N-type Si Film, 14... Oxide magnetic film, 15... Oxide semiconductor film. Applicant's agent Patent attorney Takehiko Suzue D Fig. 1 j I 2 Gate voltage Ve (mV) 3rd factor 4th prisoner Fig. 5 G 6th factor Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Figure 14 Figure 16 Figure 17 Gate voltage vG [■] Figure 18 Figure 19 Figure 20 Cause Figure 21 Figure 22 Figure 23 Figure 24

Claims (15)

[Claims] (1) A substrate, an oxide film formed on the substrate that has a channel layer that causes a superconductor-semiconductor-insulator phase transition by carrier concentration control, and a predetermined space between the oxide film and the oxide film. A superconducting transistor comprising source and drain electrodes formed therein, and a gate electrode controlling carrier concentration in a channel layer of the oxide film. (2) The superconducting transistor according to claim 1, wherein the oxide film having the channel layer is a perovskite-type oxide film containing a rare earth element. (3) The oxide film having the channel layer is an ABa_2Cu_3O_7_-_8-based film (A is Y, Y
2. The superconducting transistor according to claim 1, wherein the superconducting transistor is one of the following: b, Ho, Dy, Eu, Er, Tm, Lu. (4) The superconducting transistor according to claim 1, wherein the source and drain electrodes are formed of an oxide superconductor film. (5) The superconducting transistor according to claim 1, wherein the source and drain electrodes are formed on one surface of the oxide film, and the gate electrode is formed on the other surface of the oxide film. . (6) The superconducting transistor according to claim 1, wherein the source, drain electrode, and gate electrode are formed on the same side of the oxide film. (7) The superconducting transistor according to claim 1, wherein the gate electrode portion has an MIS structure in which a gate electrode is formed on the channel layer of the oxide film with an insulating film interposed therebetween. (8) The superconducting transistor according to claim 1, wherein the gate electrode portion has a Schottky gate structure in which the gate electrode is formed in direct contact with the channel layer of the oxide film. (9) The gate electrode is formed in direct contact with the channel layer of the oxide film, and the carrier concentration of the channel layer is controlled by carrier injection from the gate electrode. superconducting transistor. (10) The channel layer is in a high-resistance insulator or semiconductor state when the voltage applied to the gate electrode is zero, and becomes a superconductor state by applying a predetermined voltage to the gate electrode. The superconducting transistor according to item 1. (11) The channel layer is in a superconductor state when the voltage applied to the gate electrode is zero, and becomes a high-resistance insulator or semiconductor state by applying a predetermined voltage to the gate electrode. The superconducting transistor according to item 1. (12) The oxide film has a structure in which the channel layer is laminated on a magnetic oxide film.
Superconducting transistor described in Section 1. (13) A substrate, an oxide film formed on the substrate and having a channel layer that causes a superconductor-semiconductor-insulator phase transition by controlling carrier concentration, and a predetermined interval spaced between the oxide film and the oxide film. When manufacturing a superconducting transistor including the formed source and drain electrodes and a gate electrode that controls the carrier concentration of the channel layer of the oxide film,
A method for manufacturing a superconducting transistor, characterized in that the oxide film is formed by a sputtering method. (14) The oxide film is a high-resistance insulator or semiconductor in its built-in state, and ions are implanted entirely or selectively into the surface portion that will become the channel layer to form a superconductor layer. - A method for manufacturing a superconducting transistor according to claim 13, which is an on-type superconducting transistor. (15) The oxide film is a superconductor in its built-in state, and ions are implanted entirely or selectively into the surface portion that will become the channel layer to form a high-resistance insulator or semiconductor layer. 14. The method of manufacturing a superconducting transistor according to claim 13, wherein the superconducting transistor is of an off type.