JP7596650B2 - Superconducting device and manufacturing method thereof - Google Patents

Description

The present invention relates to a superconducting device and a method for manufacturing the same.

In order to integrate superconducting circuits, the use of a structure in which a superconducting circuit integrated chip carrying an integrated circuit is flip-chip mounted on a circuit board is being considered. In this structure, capacitive coupling, which can reduce the wiring of the integrated circuit, and non-contact coupling using inductive coupling are seen as promising methods to suppress signal reflection and interference and ensure the necessary signal quality (transmission characteristics).

A specific structure, for example, can be such that the superconducting integrated circuit chip is provided with the required number of capacitive coupling circuits and inductive coupling circuits for signal input and output, and non-contact coupling circuits are provided on the circuit board at corresponding positions. In order for the two non-contact coupling circuits to form a good non-contact coupling, a technique is required to couple the superconducting integrated circuit chip and the circuit board while maintaining a specified distance between them.

A technology that meets the above requirements is disclosed, for example, in Patent Document 1. In the technology of Patent Document 1, a second metal layer made of tin or tin and lead is laminated on the superconducting wiring provided on the circuit board, and the electrodes of the second metal layer are connected with solder to the electrodes of the superconducting element. In this technology, a second metal layer with good solder wettability is formed on the superconducting wiring to connect the electrodes of the superconducting element and the superconducting wiring of the circuit board. This makes it possible to obtain a highly reliable connection between the superconducting element and the circuit board.

Patent No. 2813093

However, the structure disclosed in Patent Document 1 had the problem that it was not possible to accurately control the distance between the non-contact coupling circuit of the superconducting integrated circuit chip and the non-contact coupling circuit of the circuit board. This was because there was a possibility that the position would shift while the molten solder was solidifying. As a result, there were cases where the input/output characteristics could not be obtained as designed.

The present invention was made in consideration of the above problems, and aims to provide a superconducting device that can obtain the input/output characteristics as designed with non-contact coupling, and a method for manufacturing the same.

In order to solve the above problems, the superconducting device of the present invention has a superconducting integrated circuit chip and a circuit board. The superconducting integrated circuit chip has a first electrode made of a first superconducting material and a first non-contact coupling circuit on its surface. The circuit board has a second electrode and a second non-contact coupling circuit on its surface. The second electrode has a flat upper surface and a protrusion of a first predetermined height. The protrusion has a flat upper surface and a protrusion of a second predetermined height, covered with a first thin film made of a second superconducting material, and the first thin film is covered with a second thin film made of a third superconducting material that is more ductile than the second superconducting material. The upper surface of the protrusion is directly bonded to the surface of the first electrode, and the first non-contact coupling circuit and the second non-contact coupling circuit are arranged opposite each other.

The method for manufacturing a superconducting device of the present invention uses a superconducting integrated circuit chip having a first electrode made of a first superconducting material and a first non-contact coupling circuit on its surface, and a circuit board having a second electrode made of a second superconducting material and a second non-contact coupling circuit on its surface. Then, a protrusion having a flat upper surface and a first predetermined height is formed on the second electrode. This protrusion is formed by forming a protrusion having a flat upper surface and a second predetermined height, covering this protrusion with a first thin film made of a second superconducting material, and further covering the first thin film with a third superconducting material that is more malleable than the second superconducting material. Then, the surface of the first electrode and the upper surface of the protrusion of the second electrode are directly joined, and the first non-contact coupling circuit and the second non-contact coupling circuit are arranged opposite each other.

The effect of the present invention is to provide a superconducting device that can obtain the input/output characteristics as designed with non-contact coupling, and a method for manufacturing the same.

1 is a cross-sectional view showing a configuration of a superconducting device according to a first embodiment. FIG. 11 is a plan view showing a superconducting integrated circuit chip used in a superconducting device of a second embodiment. FIG. 11 is a plan view showing a circuit board used in a superconducting device according to a second embodiment. FIG. 4 is a cross-sectional view showing a superconducting device according to a second embodiment. 5 is a cross-sectional view showing a first part of a method for manufacturing a superconducting device according to a second embodiment. FIG. 6 is a cross-sectional view showing a second part of the method for manufacturing a superconducting device according to the second embodiment. FIG. FIG. 11 is a cross-sectional view showing a third part of the method for manufacturing a superconducting device according to the second embodiment FIG. 11 is a cross-sectional view showing a superconducting device according to a third embodiment.

Below, an embodiment of the present invention will be described in detail with reference to the drawings. However, the embodiment described below has limitations that are technically preferable for implementing the present invention, but does not limit the scope of the invention to the following. Note that similar components in each drawing are given the same numbers, and descriptions may be omitted.

(First embodiment)
FIG. 1 is a cross-sectional view showing a superconducting device 1 of this embodiment. The superconducting device 1 has a superconducting integrated circuit chip 10 and a circuit board 20. The superconducting integrated circuit chip 10 has a first electrode 11 made of a first superconducting material and a first non-contact coupling circuit 12 on its surface. The circuit board 20 has a second electrode 21 and a second non-contact coupling circuit 22 on its surface. The second electrode 21 has a protrusion 21a with a first predetermined height and a flat upper surface 21b. The protrusion 21a has a flat upper surface and a protrusion 23 with a second predetermined height, covered with a first thin film 21c made of a second superconducting material, and the first thin film 21c is covered with a second thin film 21d made of a third superconducting material that is more ductile than the second superconducting material.

The upper surface 21b of the protrusion 21a is directly bonded to the surface of the first electrode 11, and the first non-contact coupling circuit 12 and the second non-contact coupling circuit 22 are arranged opposite each other.

With the above configuration, the presence of the protrusion 21a allows for precise control of the distance between the first non-contact coupling circuit 12 and the second non-contact coupling circuit. As a result, input/output characteristics can be obtained as designed with non-contact coupling. In addition, because the second thin film, which is more ductile than the first thin film, is bonded to the first electrode, damage due to stress caused by differences in the thermal expansion coefficients of the components can be suppressed at extremely low temperatures, which is the operating environment of superconducting devices. As a result, it is possible to ensure high bonding reliability.

Second Embodiment
In this embodiment, a superconducting device that is easier to handle than the first embodiment will be described. A wiring portion is provided under the second electrode provided on the circuit board. By providing the wiring portion, it is possible to improve heat dissipation and perform processing in a normal conductive state. FIG. 2 is a plan view showing a superconducting integrated circuit chip 100 used in a superconducting device. The superconducting integrated circuit chip 100 has a chip base material 101, and a first electrode 110 made of a first superconducting material and a first non-contact coupling circuit 120 are formed on the surface of the chip base material 101. The first electrode 110 is connected to, for example, a ground circuit (not shown). The first non-contact coupling circuit 120 is connected to, for example, a superconducting element (not shown). For the first superconducting material, for example, niobium, niobium nitride, aluminum, indium, lead, tin, rhenium, palladium, titanium, titanium nitride, tantalum, or an alloy containing these can be used. For example, silicon can be used for the chip base material 101. The first non-contact coupling circuit 120 is, for example, a capacitive coupling circuit or an inductive coupling circuit for inputting and outputting signals to and from the circuit board 200 .

Figure 3 is a plan view showing a circuit board 200 used in a superconducting device. The substrate base material 201 of the circuit board 200 can be made of, for example, silicon. A second electrode 210 and a second non-contact coupling circuit 220 are formed on the surface of the circuit board 200. The second electrode has a protrusion 211 having a predetermined height and a flat upper surface. The second electrode 210 has a laminated structure in which, from the side closer to the substrate of the circuit board 20, a first thin film made of a second superconducting material and a second thin film made of a third superconducting material having higher ductility than the second superconducting material are laminated. Therefore, the upper surface of the protrusion 211 shown in the plan view of Figure 3 is the second thin film. The second electrode 210 is connected, for example, to a ground circuit not shown. The second non-contact coupling circuit 220 is connected, for example, to an electronic circuit not shown. Furthermore, if the circuit board 200 is further connected to an external electronic device, the circuit board serves as an interposer.

The protrusion 211 has a smooth surface on the upper surface, and is formed so that the roughness is, for example, Ra 1 nm or less. The height of the protrusion 211 is set to a height that allows the designed input/output characteristics of the signal to be obtained between the non-contact coupling between the first non-contact coupling circuit 120 and the second non-contact coupling circuit 220. A specific numerical value can be, for example, a height of 2 μm to 10 μm.

Figure 4 is a cross-sectional view showing a superconducting device 1000 formed by joining a superconducting integrated circuit chip 100 and a circuit board 200.

The second electrode 210 of the circuit board 200 is formed by laminating a first thin film 213 made of a second superconducting material and a second thin film 214 made of a third superconducting material having higher ductility than the second superconducting material on a wiring section 230 formed on the substrate base material 201. The wiring section 230 can be formed using, for example, copper, silver, gold, platinum, or an alloy containing these. For the second superconducting material forming the first thin film, for example, niobium, niobium nitride, aluminum, lead, tin, rhenium, palladium, titanium, titanium nitride, tantalum, or an alloy containing these can be used. For the third superconducting material forming the second thin film, a material having higher ductility than the second superconducting material is used. Therefore, the choice of the third superconducting material varies depending on the second superconducting material used, but for example, if the second superconducting material is niobium, the third superconducting material can be indium.

The protrusion 211 has a structure in which the protrusion 212 formed using a material different from the second superconducting material, for example, a metal such as copper, silver, gold, platinum, or an alloy containing these, is covered with a laminated film of the first thin film 213 and the second thin film 214. Some superconducting materials such as niobium are poorly processable, and it is difficult to create a three-dimensional structure such as the protrusion 212. Therefore, the protrusion 212 can be easily formed by using a material that is easy to process. In addition, by using a material that is easy to process, the height of the protrusion 212 can be accurately controlled. Then, the height of the protrusion 211 can be accurately controlled by stacking the first thin film 213 and the second thin film 214, whose film thicknesses are accurately controlled, on the protrusion 212. Thereafter, the second electrode 210 and the protrusion 211 can be easily formed by processing the above-mentioned laminated film by photolithography, etching, or the like. In addition, in order to ensure the adhesion strength between the first thin film 213 and the wiring part 230, a base such as titanium or titanium nitride may be added. In addition, a superconducting material such as Ti may be added between the first thin film 213 and the second thin film 214 as an adhesive layer, so that the first thin film 213 is made up of multiple layers. In addition, by chamfering the periphery of the upper surface of the protrusion 212, it is possible to ensure the film-forming properties of the first thin film 213 and the second thin film 214 and to suppress damage to the thin films caused by stress concentration at the corners. In addition, the wiring section 230 may be configured to have a base layer to increase the adhesion between the wiring section 230 and the substrate base material 201.

The superconducting integrated circuit chip 100 and the circuit board 200 are connected and fixed by directly joining the first electrode 110 and the upper surface 211a of the protrusion 211. This connection is so-called face-down mounting, in which the circuit surface of the superconducting integrated circuit chip 100 faces the circuit surface of the circuit board 200. Here, the first non-contact coupling circuit 120 and the second non-contact coupling circuit 220 are accurately positioned so that they face each other. The distance between them is accurately controlled by the protrusion 211. As a result, it is possible to obtain the desired values for the capacitance in capacitive coupling and the mutual inductance in inductive coupling.

The upper surface 211a of the protrusion 211 and the first electrode 110 are joined by activating the surfaces and then bringing them into contact with each other. This technique is commonly known as room temperature bonding. This bonding creates a strong bond between the first electrode 110 and the upper surface 211a of the protrusion 211, with an amorphous layer formed at the interface by the superconducting materials that make up the first electrode 110 and the upper surface 211a of the protrusion 211. In addition, the upper surface 211a of the protrusion 211, which forms the bonding portion, is a second thin film made of a third superconducting material that is more ductile than the first thin film, so that damage due to stress caused by differences in the thermal expansion coefficients of the components can be suppressed at extremely low temperatures, which is the operating environment of superconducting devices.

In the above description, a structure in which the first thin film 213 and the second thin film 214 are not arranged on the second non-contact coupling circuit 220 has been shown, but a structure in which the first thin film 213 and the second thin film 214 are laminated on the second non-contact coupling circuit 220 may be used. In addition, the shape and arrangement of the protrusions 211 shown in FIG. 4 are not limited to this, and a polygonal column shape or the like can be applied, and they can be arranged at any position where the designed input/output characteristics are obtained. In addition, an example in which the first non-contact coupling circuit 120 and the second non-contact coupling circuit 220 are in a cross shape has been shown, but this is not a limitation and any shape can be used. In addition, an example in which four protrusions 211 are arranged around the second non-contact coupling circuit 220 has been shown, but this is not a limitation and any arrangement can be used.

Next, a method for manufacturing a superconducting device will be described. First, as shown in Fig. 5, the superconducting integrated circuit chip 100 and the circuit board 200 are placed in a vacuum chamber (not shown) with their bonding surfaces facing each other, and a vacuum is drawn. At this time, the superconducting integrated circuit chip 100 is fixed by a chip fixing jig 300. As a fixing method, a clamp method or an electrostatic chuck method can be applied. The circuit board 200 is also fixed by a substrate fixing jig 310, and a similar fixing method can be applied. The degree of vacuum in the chamber is preferably about 10 ^-6 Pa, for example.

Next, as shown in FIG. 6, an activation device 400 is used to remove adsorbed materials and oxides from the surface of the first electrode 110, which will be the joint of the superconducting integrated circuit chip 100, to activate the joint. As the activation device 400, for example, a device that irradiates ions or neutral atomic beams can be used. Similarly, the activation device 400 is used to remove adsorbed materials and oxides from the surface of the upper surface 211a of the protrusion 211, which will be the joint of the circuit board 200, to activate the joint.

Next, as shown in FIG. 7, the superconducting integrated circuit chip 100 and the circuit board 200 are aligned so that the first non-contact coupling circuit 120 and the second non-contact coupling circuit 220 face each other. Then, while maintaining the vacuum, the first electrode 110 and the upper surface 211a of the protrusion 211 are brought into contact and pressurized. The temperature may be, for example, room temperature. At this time, the first superconducting material of the first electrode 110 and the third superconducting material of the upper surface 211a of the protrusion 211 form an amorphous layer at the bonding interface, and the two are firmly bonded. Although not shown, for example, alignment marks can be provided on each of the superconducting integrated circuit chip 100 and the circuit board 200, and the positions can be adjusted using a transmitted image taken by an infrared camera, thereby aligning the two.

As described above, according to this embodiment, the non-contact coupling circuit of the superconducting integrated circuit chip and the non-contact coupling circuit of the circuit board can be mounted with a predetermined distance and highly accurately positioned. As a result, it is possible to obtain input/output characteristics according to the design values with non-contact coupling.

In addition, by bonding the ductile second thin film to the first electrode of the superconducting integrated circuit chip, damage caused by stress resulting from differences in the thermal expansion coefficients of the components in the extremely low temperatures in which the device is used can be suppressed. As a result, it is possible to ensure high bonding reliability.

In addition, in the manufacturing method of this embodiment, the bonding surfaces are activated and bonded in a vacuum, so that the first electrode surface of the superconducting integrated circuit chip and the upper surface of the protruding portion of the second electrode of the circuit board can be bonded without reoxidation. This makes it possible to form a highly reliable bond.

In addition, the second thin film on the bonding surface is malleable and its surface conforms to the roughness of the surface of the first electrode, resulting in a stable bonding state.

Furthermore, because the bonding is done at room temperature, there is no change in the state of the superconducting element due to heating, and no misalignment during mounting due to thermal expansion of the components, allowing for accurate mounting.

Third Embodiment
In the second embodiment, an example was described in which a protrusion was formed on the wiring portion of the circuit board using a material such as metal, and the protrusion was then covered with a second superconducting material thin film to form the protrusion. In the present embodiment, another method for forming the protrusion will be described.

Figure 8 is a cross-sectional view showing the superconducting device 1100 of this embodiment. The circuit board 200a used in the superconducting device 1100 of this embodiment has a protrusion 212a formed from a substrate base material 201a. A thin film of the wiring part 230a is laminated covering the protrusion 212a, and a first thin film 213 and a second thin film 214 are further laminated. Here, the first thin film 213 is a thin film of a second superconducting material as in the second embodiment, and the second thin film 214 is a thin film of a third superconducting material having higher ductility than the first thin film. By laminating these thin films and patterning them, a circuit board 200a having an external shape similar to that of the second embodiment is manufactured. For example, silicon can be used as the substrate base material 201a. Various methods for performing three-dimensional processing with high precision have been developed for silicon, and the protrusion 212a can be formed with high precision using these methods. The configuration and manufacturing method for joining the upper surface 211a of the protrusion 211 to the first electrode 110 are the same as those in the second embodiment.

As in the second embodiment, the wiring portion 230a may be made of metals such as copper, silver, gold, platinum, or alloys containing these metals. In addition, in order to ensure the adhesive strength between the first thin film 213 and the wiring portion 230a, a base such as titanium or titanium nitride may be added to the first thin film 213. In addition, a superconducting material such as Ti may be added as an adhesive layer between the first thin film 213 and the second thin film 214, and the first thin film 213 may be configured with multiple layers. In addition, by making the periphery of the upper surface of the protrusion 212 into a chamfered shape, it is possible to ensure the film formation of the thin film of the second superconducting material and to suppress damage to the thin film due to stress concentration at the corners. In addition, the wiring portion 230a may be configured to have a base layer such as titanium to increase the adhesiveness between the wiring portion 230a and the substrate base material 201a.

In the above structure, the protrusion 212a is formed from the substrate base material 201a, which is resistant to deformation (high rigidity), and the protrusion 211 is formed, so that deformation of the protrusion 211 due to pressure can be suppressed when mounting the superconducting integrated circuit chip 100. For example, silicon is a material that is less prone to deformation than copper. With the above configuration, the distance between the first non-contact coupling circuit 120 and the second non-contact coupling circuit 220 can be positioned with higher accuracy. As a result, it becomes possible to bring the input/output characteristics in non-contact coupling closer to the design values.

The present invention has been described above using the above-mentioned embodiment as an exemplary example. However, the present invention is not limited to the above-mentioned embodiment. In other words, the present invention can be applied in various aspects that can be understood by a person skilled in the art within the scope of the present invention.

A part or all of the above-described embodiments can be described as, but is not limited to, the following supplementary notes.
(Appendix 1)
a superconducting integrated circuit chip having a first electrode made of a first superconducting material and a first non-contact coupling circuit on a surface thereof;
a circuit board having a second electrode on a surface thereof, the second electrode having a protrusion with a first predetermined height, and a second non-contact coupling circuit;
having
the protrusion has a structure in which a protrusion having a second predetermined height is covered with a first thin film made of a second superconducting material, and the first thin film is covered with a second thin film made of a third superconducting material having higher ductility than the second superconducting material;
a surface of the first electrode and an upper surface of the protrusion of the second electrode are directly bonded to each other;
A superconducting device, characterized in that the first non-contact coupling circuit and the second non-contact coupling circuit are disposed opposite each other.
(Appendix 2)
2. The superconducting device according to claim 1, wherein the protrusion is made of the same material as a base material of the circuit board.
(Appendix 3)
3. The superconducting device according to claim 1 or 2, wherein a joint between the first electrode and the protruding portion of the second electrode has an amorphous layer containing the first superconducting material and the third superconducting material.
(Appendix 4)
4. The superconducting device according to claim 1, wherein the upper surface of the protrusion has an arithmetic mean roughness Ra of 1 nm or less.
(Appendix 5)
5. The superconducting device according to claim 1, wherein the outer periphery of the upper surface of the protrusion is formed into an arc-shaped chamfer.
(Appendix 6)
6. The superconducting device according to claim 1, wherein the first electrode and the second electrode are ground electrodes.
(Appendix 7)
7. The superconducting device according to claim 1, wherein the second superconducting material is niobium.
(Appendix 8)
8. The superconducting device according to claim 1, wherein the third superconducting material is indium.
(Appendix 9)
A method for manufacturing a superconducting device having a superconducting integrated circuit chip having a first electrode made of a first superconducting material and a first non-contact coupling circuit on a surface thereof, and a circuit board having a second electrode made of a second superconducting material and a second non-contact coupling circuit on a surface thereof, comprising:
forming a protrusion having a flat upper surface and a first predetermined height on the second electrode;
The protrusion has a flat upper surface and a second predetermined height, the protrusion is covered with a first thin film made of a second superconducting material, and the first thin film is covered with a third superconducting material having a higher malleability than the second superconducting material,
directly bonding a surface of the first electrode and an upper surface of the protrusion of the second electrode;
a first non-contact coupling circuit and a second non-contact coupling circuit disposed opposite each other;
(Appendix 10)
The superconducting integrated circuit chip and the circuit board are placed in a chamber with the first electrode and the second electrode facing each other;
The chamber is evacuated,
activating the first electrode and the upper surface of the protrusion of the second electrode;
Aligning the first non-contact coupling circuit and the second non-contact coupling circuit so that they face each other;
while maintaining the vacuum level of the chamber, the first electrode and an upper surface of the protrusion of the second electrode are brought into contact with each other and pressurized.
10. A method for manufacturing a superconducting device according to claim 9.
(Appendix 11)
The method for manufacturing a superconducting device according to claim 9 or 10, wherein the protrusion is formed from the same material as a base material of the circuit board.
(Appendix 12)
12. The method for manufacturing a superconducting device according to claim 9, wherein the upper surface of the protrusion has an arithmetic mean roughness Ra of 1 nm or less.
(Appendix 13)
13. The method for manufacturing a superconducting device according to any one of claims 9 to 12, wherein an outer periphery of the upper surface of the protrusion is formed into an arc-shaped chamfer.
(Appendix 14)
14. The method for manufacturing a superconducting device according to any one of claims 9 to 13, wherein the second superconducting material is niobium.
(Appendix 15)
15. The method for manufacturing a superconducting device according to any one of claims 9 to 14, wherein the third superconducting material is indium.

REFERENCE SIGNS LIST 1, 1000, 1100 Superconducting device 10, 100 Superconducting integrated circuit chip 11, 110 First electrode 12, 120 First non-contact coupling circuit 20, 200, 200a Circuit board 21, 210 Second electrode 21a, 211 Protrusion 21b, 211a Top surface 21c, 213 First thin film 21d, 214 Second thin film 22, 220 Second non-contact coupling circuit 23, 212, 212a Protrusion 101 Chip base material 201, 201a Substrate base material 212, 212a Protrusion 230, 230a Wiring portion 300 Chip fixing jig 310 Substrate fixing jig 400 Activation device

Claims (9)

a superconducting integrated circuit chip having a first electrode made of a first superconducting material and a first non-contact coupling circuit on a surface thereof;
a circuit board having a second electrode on a surface thereof, the second electrode having a protrusion with a first predetermined height, and a second non-contact coupling circuit;
having
the protruding portion has a structure in which a protrusion having a second predetermined height is covered with a first thin film made of a second superconducting material, and the first thin film is covered with a second thin film made of a third superconducting material having higher ductility than the second superconducting material;
a surface of the first electrode and an upper surface of the protrusion of the second electrode are directly bonded to each other;
the first non-contact coupling circuit and the second non-contact coupling circuit are disposed opposite to each other,
The protrusion is made of the same material as the base material of the circuit board.
A superconducting device comprising: 2. The superconducting device according to claim 1, wherein a joint between the first electrode and the protruding portion of the second electrode has an amorphous layer containing the first superconducting material and the third superconducting material. 3. The superconducting device according to claim 1, wherein the upper surface of the protrusion has an arithmetic mean roughness Ra of 1 nm or less. 4. The superconducting device according to claim 1 , wherein an outer periphery of the upper surface of the protrusion is formed into an arc-shaped chamfer. 5. The superconducting device according to claim 1, wherein the first electrode and the second electrode are ground electrodes. 6. The superconducting device of claim 1, wherein the second superconducting material is niobium. 7. The superconducting device according to claim 1, wherein the third superconducting material is indium. A method for manufacturing a superconducting device having a superconducting integrated circuit chip having a first electrode made of a first superconducting material and a first non-contact coupling circuit on a surface thereof, and a circuit board having a second electrode made of a second superconducting material and a second non-contact coupling circuit on a surface thereof, comprising:
forming a protrusion having a flat upper surface and a first predetermined height on the second electrode;
the protrusion is formed by three-dimensionally processing a surface of a base material of the circuit board to form a protrusion having a flat upper surface and a second predetermined height, covering the protrusion with a first thin film made of a second superconducting material, and covering the first thin film with a third superconducting material having higher ductility than the second superconducting material;
directly bonding a surface of the first electrode and an upper surface of the protrusion of the second electrode;
a first non-contact coupling circuit and a second non-contact coupling circuit disposed opposite each other; The superconducting integrated circuit chip and the circuit board are placed in a chamber with the first electrode and the second electrode facing each other;
The chamber is evacuated,
activating the first electrode and the upper surface of the protrusion of the second electrode;
Aligning the first non-contact coupling circuit and the second non-contact coupling circuit so that they face each other;
while maintaining the vacuum level of the chamber, the first electrode and an upper surface of the protrusion of the second electrode are brought into contact with each other and pressurized.
9. The method of claim 8, wherein the superconducting device is made of a material selected from the group consisting of fluororesin, ...rubber, and fluororesin.

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