JPH02194665A - Field effect superconducting device and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable the gap between a source and a drain to be widened for facilitating the manufacture of the title device by a method wherein an oxide high temperature superconducting material is used for the source, the drain, etc. CONSTITUTION:The title device is provided with a thin film 2 comprising an oxide high temperature superconducting region 2S, a normal conductive region 2NS, another oxide high temperature superconducting region 2C, another normal conductive region 2ND and the other oxide high temperature superconducting region 2D as well as a gate electrode 4G formed on the surface or rear surface of the oxide high temperature superconducting region held by the normal conductive regions 2NS and 2ND in the shifting direction of a Cooper pair formed on an insulating substrate 1. Through these procedures, a source, a drain, etc., are composed of the oxide high temperature superconducting material to be operated without depending upon the approximation effect thereof, thereby enabling the gap between the source and the drain to be widened.

Description

[Detailed Description of the Invention] [Summary] Regarding the improvement of a field effect superconducting device using an oxide high temperature superconducting material and its manufacturing method, a source, a drain, etc. are composed of an oxide high temperature superconducting material, and further, The aim is to realize a field-effect superconducting device that operates without relying on such proximity effects and is therefore easy to manufacture. A thin film consisting of a high temperature superconducting region, a normal conducting region, an oxide high temperature superconducting region, a normal conducting region and an oxide high temperature superconducting region, and a gate insulating layer on the surface of the oxide high temperature superconducting region sandwiched between the normal conducting regions. The structure is such that a gate electrode formed through a film can be obtained.

[Industrial application field]

The present invention relates to an improvement in a field effect superconducting device using an oxide high temperature superconducting material and a method for manufacturing the same.

Oxide high-temperature superconductors have a critical temperature T exceeding the boiling point of liquid nitrogen (77 (K)), and are therefore expected to have various applications in the field of electronics.

Currently, as one of its applications, the realization of a three-terminal device that operates similarly to a field-effect transistor using a semiconductor is being considered.

[Prior Art] FIG. 15 shows a cutaway side view of essential parts of a field effect superconducting device for explaining the conventional art.

In the figure, 11 is an n-type silicon semiconductor substrate, 12 is an insulating film made of silicon dioxide (SiOz), 13 is a source made of niobium (Nb), 14 is the same (a drain made of Nb, and 15 is made of SiO2) gate insulating film,
I6 is a gate electrode made of metal such as Aβ, LcN is n
A channel region is generated on the surface of the type silicon semiconductor substrate 11, S indicates a source terminal, G indicates a gate terminal, and D indicates a drain terminal. Note that the length of the channel region LCH is, for example, about 0.1 cμm.

In this superconducting device, the current flowing from the drain electrode 14 to the source electrode 13 through the channel region LcH is controlled by the voltage applied to the gate electrode 16.
Its operation is similar to a normal field effect transistor.

[Problem to be solved by the invention]

In order to operate the field-effect superconducting device shown in Figure 15 in a superconducting state, it must be operated at the liquid helium (1-1e) temperature at which Nb becomes superconducting, and a lot of energy is required to cool it down. It costs money.

Therefore, in recent years, attempts have been made to replace Nb with oxide high-temperature superconducting materials to create field-effect superconducting devices that can operate at much higher temperatures than conventional ones, such as liquid nitrogen (N2) temperatures. ing.

However, it is impossible to obtain a practical device by simply changing the source electrode 13 and drain electrode 14 in the field-effect superconducting device shown in FIG. 15 to oxide high-temperature superconducting materials. be.

The reason for this is that the oxide high-temperature superconductors that are currently attracting attention are so-called ceramics, and their coherence length is very short, about 1 (nm).
In devices that utilize the proximity effect of the source electrode 13 and drain electrode 14, such as the field-effect superconducting device shown in Figure 5, it is necessary to significantly narrow the gap, which is difficult to achieve with current technology. Although it is not impossible to realize such a gear knob, the reproducibility is extremely poor. Note that the coherence length of Nb is approximately 10 (n m
), the gap can be widened accordingly, and the field-effect superconducting device shown in the figure is thereby realized.

The present invention realizes a field-effect superconducting device in which the source, drain, etc. are composed of oxide high-temperature superconducting materials, and in which the operation does not depend on the proximity effect (and is therefore easy to manufacture). We are trying to provide the technology to do so.

[Means to solve the problem]

Needless to say, the present invention has a great advantage in that the critical temperature T of the oxide high temperature superconducting material is high, but in addition, the oxide high temperature superconducting material has a low carrier concentration. It is constructed by taking advantage of the characteristics of In other words, if the channel region made of high-temperature oxide superconducting material has a low carrier concentration, the depletion layer can expand significantly by applying a small voltage, and the operating state of the field-effect superconducting device can be changed. be. In addition, Cooper pairs moving from the source to the drain in a field-effect superconducting device use a tunneling phenomenon, so unlike those that use the proximity effect, the Cooper pairs move from the source to the drain.

There is no need to form an extremely narrow space between drains.

For this reason, in the field effect superconducting device and the manufacturing method thereof of the present invention, an oxide high temperature superconducting region (for example, a source 2S ), a normal conducting region (e.g. normal conducting region 2.3), an oxide high temperature superconducting region (e.g. channel region 2C), and a normal conducting region (e.g. normal conducting region 2.
,,) and oxide high temperature superconducting regions (e.g. drain 2D)
Thin M consisting of! (For example, B15rCaCuO film 2)
and a gate electrode (e.g., gate electrode 4G or 5G) formed also on the surface or back surface of the oxide high-temperature superconducting region sandwiched between the normal-conducting regions via a gate insulating film (e.g., gate insulating film 3 or 6). It is structured so that you can get what you want.

[Effect]

By adopting the above-mentioned means, it is possible to realize a device in which the source, drain, etc. are made of an oxide high-temperature superconducting material, and which operates without depending on the proximity effect of these materials,
Therefore, the distance between the source and drain can be widened, and manufacturing is easy.

〔Example〕

FIG. 1 shows a cutaway side view of essential parts for explaining one embodiment of the present invention.

In the figure, 1 is a substrate made of magnesium oxide (MgO), 2S is a source made of B15rCaCuO, and 2D
is a drain made of B15rCaCuO, 2C is B15
Channel region consisting of rCaCuO, 2 NO+ 2
83 is a normal conduction region, 3 is a gate insulating film made of MgO,
4S indicates a source electrode made of Au, 4G a gate electrode made of Aβ, and 4D a drain electrode made of Au.

As is clear from the figure, in this embodiment, source 2
The superconducting region (S) and the normal conducting region (N
) - superconducting region (S) - normal conducting region (N) - superconducting region (S), and has a 5-N-3-N-3 configuration.

Here, when a voltage is applied to the gate electrode 4G, the superconducting phase of the channel region 2C is broken, and a depletion layer is generated from the interface between the channel region 2C and the gate insulating film 3 in the depth direction of the channel region 2C. As the voltage applied to the gate electrode 4G increases, the depletion layer expands, and the depletion layer expands from the interface to 5 to 1
0 (nm) or so, and the 5-N
-5-N-3 configuration substantially changes to 5-N-5 configuration.

In this embodiment, the above phenomenon is utilized to change the voltage/current characteristics of a field effect superconducting device.

FIG. 2 is a diagram for explaining the voltage/current characteristics of an embodiment of the present invention in conjunction with FIG. 1, with the horizontal axis representing the voltage V and the vertical axis representing the current I. .

In the figure, the characteristic line indicated by O indicates the case where no voltage is applied to the gate electrode 4G, and the characteristic line indicated by ``O'' indicates the case where there is.

By utilizing such irreversible characteristics, the gate electrode 4
It will be understood that depending on the presence or absence of a voltage applied to G, this field effect superconducting device can perform a switching operation.

FIG. 3 shows a cutaway side view of essential parts for explaining another embodiment of the present invention, and the same symbols as those used in FIG. 1 indicate the same parts or have the same meanings. shall be.

In the figure, 5G indicates a gate electrode on the back side, and 6 indicates a gate insulating film on the back side.

In this embodiment, since the gate electrode 4G is formed on the front side of the channel region 2C and the gate electrode 5G is formed on the back side, a voltage is applied to the gate electrodes 4G and 5G to form the channel region 2C. When expanding the depletion layer to
The purpose can be easily achieved with low voltage.

Many modifications can be made to any of the embodiments, for example: (1) For the substrate 1, in addition to MgO, an insulating material that is compatible with oxide high temperature superconducting materials such as 5rTi03 may be appropriately selected; ■ Source 2S, drain 2D and channel region 2C
In addition to B15rCaCuO, TNBaCaCuO
2. The source 28 can be used as the normal conduction regions 2HD and 285.
The oxide high-temperature superconducting material used for such applications can be converted into a normal conducting material by plasma treatment, and semiconductors and insulators can be used; ■ The gate insulating film 3 can be made of insulating materials such as Zr0z, BaF2, or YF in addition to Mg0O. Being able to use , etc.

Figures 4 to 8 are cross-sectional side views of the main parts of a field effect superconducting device at key points in the process for explaining other embodiments of the present invention, and these figures will be described below. I will explain while referring to it. Note that the same symbols as those used in FIGS. 1 to 3 indicate the same parts or have the same meanings.

Refer to FIG. 4 (1) For example, by applying an ion beam sputtering method, a B15rCaCuO film 2 having a thickness of, for example, about 100 [people] is formed on an MgO substrate 1.

The main conditions when performing ion beam sputtering are as follows: Extraction voltage: 2.4 (KV) Total current: 20 (mA) Discharge voltage 70.5 (KV) Discharge current: 10 (mA) Discharge voltage crab 5X10-' [Torr] Gas: Ar Deposition rate: 20 [people/min].

In this process, in addition to the ion beam sputtering method, chemical vapor deposition (chemical vapor deposition)
or deposition:CVD) method, molecular beam epitaxial growth (m.

1ecular beam epitaxy:
Any suitable technique such as the MICE method, sputtering method, or multi-component vapor deposition method may be used.

(2) By applying a resist process in photo-phosphorography technology, a photo-resist film 7 having a thickness of, for example, about 5 [μrn] is formed to cover a portion that is to become an element region.

(3) For example, reactive ion etching using CCβ4 as the etching gas.
The B15rCaCuO film 2 is patterned by using the RIE (etching: RIE) method.

The applied power in this case is, for example, 0. 5(W/c
m”).

In this process, in addition to the RIE method, the etchant is
A wet etching method using NO3 or a method using a plasma polymerized film (see Japanese Patent Application No. 63-40079 if necessary) can be applied.

See Figure 6 (4) Photo used as an etching mask
After removing the resist film 7, a resist process using photolithography is applied again to form a photoresist film (not shown) having an opening in the area where the channel region is to be formed.

(5) By applying the magnetron sputtering method, M with a thickness of, for example, about 100 to 500
A gate insulating film 3 made of gO is formed.

(6) The gate insulating film 3 is patterned by a lift-off method by dissolving and removing the photoresist film.

Refer to FIG. 7 (7) By applying a resist process in photolithography, a photoresist film 8 having an opening in a portion where a normal conduction region is to be formed is formed. Note that the photoresist film 8 can be replaced with other materials, such as a suitable metal.

(8) Set in a parallel plate type RIE apparatus and perform plasma treatment to convert a part of the B15rCaCuO film 2 into a normal conduction region 2N.

Examples of main conditions in this case are as follows.

Gas: Ar (or N2) application type crab 0. 5 (W/cm") Incidentally, since this treatment only needs to damage the B15rCaCuO film 2, ion implantation can also be applied instead of gas plasma treatment.

After this process, a source 2S, a channel region 2C, and a drain 2D are defined in the B15rCaCuO film 2, respectively.

Refer to FIG. 8 (9) By applying a conventional technique such as a vacuum evaporation method and a lift-off method or a vacuum evaporation method and an RIE method, a gate electrode 4G and a source electrode 4 made of Ae or the like are formed.
S. Form a drain electrode 4D.

In this way, a 5-N-5-N-5 configuration is easily realized.

FIG. 9 shows a cutaway side view of essential parts for explaining another embodiment of the present invention, and the same symbols as those used in FIGS. 1 to 8 indicate the same parts or have the same meanings. shall have.

In the figure, 9S indicates a source, and 9D indicates a drain.

As is clear from the figure, in this embodiment, the source 9S and drain 9D are formed separately later.

Figures 10 to 14 represent cutaway side views of essential parts of a field-effect superconducting device at important process points for explaining other embodiments of the present invention, and these figures will be described below. I will explain while referring to it. Note that the same symbols as those used in FIGS. 1 to 9 indicate the same parts or have the same meanings.

Refer to Figure 10+11 By applying the ion beam sputtering method, a thickness of, for example, 100 [
A YBaCuOX film 2N having a thickness of about 1000 yen is formed. Note that this YBaCuO* film 2N has a normal conduction phase, and to create it, heat treatment is performed in an N2 atmosphere, or
Ar plasma treatment may be performed to lower the X value in OX.

The main conditions when performing ion beam sputtering are as follows: Extraction voltage: 2.4 (KV) Total current: 20 (mA) Discharge voltage: 0.5 (KV) Discharge current: 10 (mA) Discharge voltage Crab 5×10-' [Torr] Gas: Ar Deposition rate: 20 [people/min].

In this step, in addition to the ion beam sputtering method, an appropriate technique such as a CVD method, an MBE method, a sputtering method, or a multi-dimensional vapor deposition method may be used.

(2) By applying a resist process in photolithography technology, a photoresist film 7 having a thickness of, for example, about 5 [μm] is formed to cover a portion that is to become an element region.

See Figure 11 (3) For example, R using CCl4 as the etching gas.
The YBaCuOX film 2N patterning is performed by applying the rE method.

The applied force in this case is, for example, 0.5 (W/c+
++”).

In this process, in addition to the RIE method, the etchant is
A wet etching method using NO3 can be applied, or a method using a plasma polymerized film can be applied.

See Figure 12 (4) Photo mask used as an etching mask.
After removing the resist film 7, a resist process using photolithography is applied again to form a photoresist film (not shown) with openings in the areas (three locations) where the normal conduction region is to be formed. form.

(5) By applying a magnetron sputtering method, an insulating film 3' made of MgO and having a thickness of, for example, about 100 to 500 [people] is formed.

(6) Buttering the insulating film 3' by a lift-off method by dissolving and removing the photoresist film.

Refer to FIG. 13 (7) Place the film into a parallel plate type RIE apparatus and perform plasma treatment to convert a part of the Y Ba Cu OX film 2N into a superconducting region.

Examples of main conditions in this case are as follows.

Gas: 02 Application type crab 0. 2 (W/cm2) After this process, a source 2S, a channel region 2C, and a drain 2D are defined in the YBaCuOx film 2, respectively.

See FIG. 14 (8) A photoresist film (not shown) having an opening on the channel region 2C is formed by applying a resist process in photolithography.

(9) By applying a magnetron sputtering method, a gate insulating film 3 made of MgO with a thickness of, for example, about 100 to 500 mm is formed.

The gate insulating film 3 is patterned by a lift-off method by dissolving and removing the 0ω photoresist film.

00 A gate electrode 4G and a source electrode 4S made of Al or the like are formed by applying a conventional technique such as a vacuum evaporation method and a lift-off method or a vacuum evaporation method and an RIE method.
, forming a drain electrode 4D.

Even in this case, the 5-N-3-N-3 configuration can be easily realized, similar to the embodiment described with reference to FIGS. 4 to 8.

In the present invention, in addition to the above-described embodiments, other structures can be easily manufactured. For example, the double gate electrode structure explained with reference to FIG. This can be realized by forming the gate electrode ti5G on the back surface side and the gate insulating film 6 covering it, and then going through the same steps as the embodiment described with reference to FIGS. 4 to 8.

〔Effect of the invention〕

In the field-effect superconducting device and the manufacturing method thereof according to the present invention, an oxide high-temperature superconducting region, a normal-conducting region, and an oxide high-temperature superconducting region are formed on an insulating substrate and sequentially in the moving direction of Cooper pairs. A thin film consisting of a normal conducting region and an oxide high temperature superconducting region, and a gate electrode formed also on the surface or back surface of the oxide high temperature superconducting region sandwiched between the normal conducting region via a gate insulating film. It is structured so that you can get something.

By adopting the above configuration, it is possible to realize a device in which the source, drain, etc. are made of an oxide high-temperature superconducting material, and which operates without depending on the proximity effect of these materials,
Therefore, the distance between the source and drain can be widened, and manufacturing is easy.

[Brief explanation of the drawing]

FIG. 1 is a cutaway side view of essential parts of a field-effect superconducting device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the voltage vs. current characteristics of the embodiment shown in FIG. Figure 3 is a cutaway side view of essential parts of a field-effect superconducting device that is another embodiment of the present invention, and Figures 4 to 8 are key steps for explaining the manufacturing method that is one embodiment of the present invention. FIG. 9 is a cut-away side view of the main part of a field-effect superconducting device according to an embodiment of the present invention, and FIGS. A cut-away side view of the main part of a field-effect superconducting device at key points in the process for explaining the manufacturing method as an example, and FIG. 15 is a cut-away side view of the main part of a conventional field-effect superconducting device. Each represents a diagram. In the figure, 1 is a substrate made of MgO, 2S is B15r
Source consisting of CaCuO, 2D is the same <B15rCa
Drain made of CuO, 2C is the same <B15rCaC
A channel region made of uO, 2ND+2N3 a normal conduction region, 3 a gate insulating film made of MgO, 4S a source electrode made of Au, 4G a gate electrode made of Al, and 4D a drain electrode made of Au. ing. Patent applicant: Fujitsu Ltd. Representative Patent Attorney Shoji Aitani

Claims (4)

[Claims] (1) A thin film formed on an insulating substrate and consisting of an oxide high temperature superconducting region, a normal conducting region, an oxide high temperature superconducting region, a normal conducting region, and an oxide high temperature superconducting region in order in the moving direction of the Cooper pair. A field effect superconducting device comprising: a gate electrode formed on the surface of an oxide high temperature superconducting region sandwiched between the normal conducting regions with a gate insulating film interposed therebetween. (2) The field-effect superconducting device according to claim (1), further comprising a gate electrode formed on the back surface of the oxide high-temperature superconducting region sandwiched between the normal-conducting regions via a gate insulating film. (3) Forming an oxide high-temperature superconducting material film on an insulating substrate, and then selectively plasma-treating the oxide high-temperature superconducting material film to sandwich a channel region made of the oxide high-temperature superconducting material. A method for manufacturing a field-effect superconducting device, comprising the step of forming a normal-conducting region and a source and drain made of an oxide high-temperature superconducting material sandwiching the normal-conducting region. (4) A step of forming a normal conducting material film on an insulating substrate, and then selectively plasma-treating the normal conducting material film to form a normal conducting region sandwiching a channel region made of an oxide high temperature superconducting material, etc. 1. A method for manufacturing a field-effect superconducting device, comprising the step of forming a source and a drain made of an oxide high-temperature superconducting material sandwiching a source and a drain.