JP7600546B2 - 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 amount of wiring in 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 made of a second superconducting material and a second non-contact coupling circuit on its surface. The second electrode has a flat upper surface and a protrusion of a predetermined height. 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. A protrusion having a flat upper surface and a predetermined height is then formed on the second electrode, and the surface of the first electrode and the upper surface of the protrusion are directly joined to place the first non-contact coupling circuit and the second non-contact coupling circuit 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
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 made of a second superconducting material and a second non-contact coupling circuit 22 on its surface. The second electrode 21 has a protrusion 21a with a flat upper surface and a predetermined height. The upper surface 21b of the protrusion 21a is directly joined 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 to face each other.

With the above configuration, the presence of the protrusion 21a allows the distance between the first non-contact coupling circuit 12 and the second non-contact coupling circuit to be accurately controlled. As a result, input/output characteristics can be obtained as designed with non-contact coupling.

Second Embodiment
In this embodiment, a superconducting device that is easier to manufacture than the first embodiment will be described. FIG. 2 is a plan view showing a superconducting integrated circuit chip 100 used in the 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 a 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, for example, silicon. A second electrode 210 made of a second superconductor material and a second non-contact coupling circuit 220 are formed on the surface of the circuit board 200. The second electrode 210 has a protrusion 211 having a predetermined height and a flat upper surface. The second superconducting material can be, for example, niobium, niobium nitride, aluminum, indium, lead, tin, rhenium, palladium, titanium, titanium nitride, tantalum, or an alloy containing these. 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). Note that when the circuit board 200 is further connected to an external electronic device, the circuit board plays the role of 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 thin film of a second superconducting material on the 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. By providing the wiring section, it is possible to improve heat dissipation and perform processing in a normal conductive state. The protrusion section 211 is formed by laminating a thin film of the second superconducting material on the protrusion section 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. Some superconducting materials such as niobium are poorly processable, and it is difficult to create a three-dimensional structure such as the protrusion section 212. Therefore, the protrusion section 212 can be easily formed by using a material that is easy to process. In addition, the height of the protrusion section 212 can be accurately controlled by using a material that is easily processable. Then, by stacking a thin film of the second superconducting material with an accurately controlled thickness on the protrusion 212, the height of the protrusion 211 can be accurately controlled. After that, the thin film of the second superconducting material is processed by photolithography, etching, or the like, to easily form the second electrode 210 and the protrusion 211. In addition, a base such as titanium or titanium nitride may be added to ensure the adhesive strength between the second electrode 210 and the wiring part 230. 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 part 230 may be configured to have a base layer to increase the adhesiveness between the wiring part 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 bonded by activating the surfaces and then bringing them into contact. 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 material that constitutes each of them.

In the above description, a structure in which the second superconducting material thin film is not disposed on the second non-contact coupling circuit 220 has been shown, but a structure in which the second superconducting material thin film is laminated on the second non-contact coupling circuit 220 may also 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 also be applied, and they can be disposed 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 shaped like a cross 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 disposed 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 second 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, it is possible to obtain the signal input/output characteristics as designed with non-contact coupling. This is because the second electrode of the circuit board has a protrusion of a predetermined height with a flat upper surface, so that the non-contact coupling circuit of the superconducting integrated circuit chip and the non-contact coupling circuit on the circuit board can be mounted with a predetermined distance between them and positioned with high precision.

In addition, high bonding reliability and performance can be ensured. This is because activating and bonding the bonding surfaces in a vacuum allows the surfaces of the first and second electrodes to be bonded without reoxidation. Furthermore, because bonding is performed at room temperature, there is no change in the state of the superconducting element due to heating, and no misalignment of the mounting position due to thermal expansion of the components, and high performance can be maintained.

Furthermore, when the first and second superconducting materials are the same material, high joint reliability can be ensured even in operation in an extremely low temperature environment. This is because the same superconducting materials are directly joined together. With this configuration, damage due to stress caused by differences in the thermal expansion coefficients of the components can be suppressed, particularly at the extremely low temperatures (10 mK) in which superconducting circuits are used.

In addition, stable electrical properties can be ensured. This is because by joining the same superconducting materials together, no compound layer that inhibits the superconducting properties is formed at the joining interface.

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 portion 230a is then laminated over the protrusion 212a, and a thin film of a second superconducting material is further laminated and patterned to produce a circuit board 200a having an external shape similar to that of the second embodiment. For example, silicon can be used as the substrate base material 201a. Various methods for performing three-dimensional processing with high accuracy have been developed for silicon, and these methods can be used to form the protrusion 212a with high accuracy. 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 of the second embodiment.

As in the second embodiment, the wiring portion 230a can be made of metals such as copper, silver, gold, platinum, or alloys containing these metals. In addition, a base such as titanium or titanium nitride may be added to ensure the adhesive strength between the second electrode 210 and the wiring portion 230. 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 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 of Ti or the like to increase the adhesiveness between the wiring portion 230a and the substrate base material 201a.

By forming the protrusion 212a from the substrate base material 201a, which is resistant to deformation (high rigidity), and forming the protrusion 211, 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 of the 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 made of a second superconducting material and a second non-contact coupling circuit on a surface thereof;
having
the second electrode has a protrusion having a predetermined height and a flat upper surface;
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 a protrusion made of a material different from the second superconducting material is disposed inside the second superconducting material covering an upper surface of the protrusion.
(Appendix 3)
3. The superconducting device according to claim 2, wherein the different material is the same material as a base material of the circuit board.
(Appendix 4)
3. The superconducting device of claim 2, wherein the different material is a metal.
(Appendix 5)
5. The superconducting device according to claim 1, wherein a joint between the first electrode and the protrusion of the second electrode has an amorphous layer containing the first superconducting material and the second superconducting material.
(Appendix 6)
6. 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 7)
7. 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 8)
8. The superconducting device according to claim 1, wherein the first electrode and the second electrode are ground electrodes.
(Appendix 9)
9. The superconducting device according to any one of claims 1 to 8, wherein at least one of the first superconducting material and the second superconducting material is Nb.
(Appendix 10)
10. The superconducting device according to any one of claims 1 to 9, wherein the first superconducting material and the second superconducting material are the same superconducting material.
(Appendix 11)
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 predetermined height and a flat upper surface on the second electrode;
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 12)
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 the protrusion of the second electrode are brought into contact with each other and pressurized.
12. A method for manufacturing a superconducting device according to claim 11.
(Appendix 13)
13. The method for manufacturing a superconducting device according to claim 11 or 12, further comprising forming a protrusion on the circuit board using a material different from the second superconducting material, and covering the protrusion with the second superconducting material to form the raised portion.
(Appendix 14)
14. The method for manufacturing a superconducting device according to claim 13, wherein the different material is the same material as a base material of the circuit board.
(Appendix 15)
14. The method for manufacturing a superconducting device according to claim 13, wherein the different material is a metal.
(Appendix 16)
16. The method for manufacturing a superconducting device according to any one of claims 11 to 15, wherein the upper surface of the protrusion has an arithmetic mean roughness Ra of 1 nm or less.
(Appendix 17)
17. The method for manufacturing a superconducting device according to any one of claims 11 to 16, wherein an outer periphery of the upper surface of the protrusion is formed into an arc-shaped chamfer.
(Appendix 18)
18. The method for manufacturing a superconducting device according to any one of claims 11 to 17, wherein at least one of the first superconducting material and the second superconducting material is Nb.
(Appendix 19)
19. The method for manufacturing a superconducting device according to any one of claims 11 to 18, wherein the first superconducting material and the second superconducting material are the same superconducting material.

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 Circuit board 21, 210 Second electrode 21a, 211 Protrusion 21b, 211a Top surface 22, 220 Second non-contact coupling circuit 201, 201a Board base material 212, 212a Protrusion 230 Wiring section 300 Chip fixing jig 310 Board fixing jig 400 Activation device

Claims (8)

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 made of a second superconducting material and a second non-contact coupling circuit on a surface thereof;
having
the second electrode has a protrusion having a predetermined height and a flat upper surface;
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,
a material different from the second superconducting material is disposed under the second superconducting material covering the upper surface of the protrusion;
The different material is 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 an upper surface of the protrusion of the second electrode has an amorphous layer containing the first superconducting material and the second 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 according to claim 1, wherein the first superconducting material and the second superconducting material are the same superconducting material. 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 predetermined height and a flat upper surface on the second electrode;
directly bonding a surface of the first electrode and an upper surface of the protrusion of the second electrode;
The first non-contact coupling circuit and the second non-contact coupling circuit are disposed opposite each other ;
1. A method for manufacturing a superconducting device, comprising:
the protrusion is formed by laminating the second superconducting material on a material different from the second superconducting material,
The different material is the same material as the base material of the circuit board.
A method for manufacturing a superconducting device comprising the steps of: 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 the protrusion of the second electrode are brought into contact with each other and pressurized.
8. The method of claim 7, wherein the superconducting device is made of a material selected from the group consisting of fluororesin, fluororesin, fluorosilane, fluororesin, fluororesin.

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