Superconducting device and superconducting device apparatus

Abstract

A superconducting device according to the present disclosure comprises a laminate having a first base material wiring layer. The first base material wiring layer has a first main surface and a second main surface positioned on the side opposite from the first main surface, and has a first insulating layer and a conductor. The first insulating layer is made of a ceramic. Within the conductor, a wiring-form conductor disposed so as to follow one of the two main surfaces of the first insulating layer is a superconductor. The one of the two main surfaces of the first insulating layer is a smooth surface having a surface roughness Ra of 0.1 μm or less.

Description

Superconducting device and superconducting device apparatus

[0001] The present disclosure relates to superconducting devices and superconducting device apparatus.

[0002] Conventionally, packaging technologies for mounting superconducting elements such as Josephson elements have been known. Patent Document 1 discloses a package for mounting a superconducting element in which a superconducting element such as a Josephson element is mounted on a substrate having a conductor layer inserted between ceramic layers.

[0003] Japanese Patent Application Publication No. 01-298608

[0004] A superconducting device according to one aspect of the present disclosure includes a laminate having a first substrate wiring layer. The first substrate wiring layer has a first main surface and a second main surface opposite the first main surface, and also has a first insulating layer and a conductor, the first insulating layer being made of ceramic. Among the conductors, a wiring-like conductor arranged along one of the two main surfaces of the first insulating layer is a superconductor. One of the two main surfaces of the first insulating layer is a smooth surface with a surface roughness Ra of 0.1 μm or less.

[0005] FIG. 1 is a perspective view schematically showing an example of the configuration of a superconducting device according to an embodiment. FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1. FIG. 3 is a perspective view schematically showing the arrangement of wiring conductors on the second main surface of a first substrate wiring layer. FIG. 4 is a cross-sectional view schematically showing a laminated structure of a first insulating layer of a first substrate wiring layer, a wiring conductor, and a second insulating layer of a second substrate wiring layer. FIG. 5 is a schematic diagram showing a method for determining surface roughness. FIG. 6 is a cross-sectional schematic view showing another aspect of a superconducting device. FIG. 7 is a perspective view schematically showing an example of the configuration of a superconducting device according to an embodiment. FIG. 8 is a cross-sectional view taken along line B-B in FIG. 7.

[0006] Hereinafter, a detailed description will be given of a superconducting device and a superconducting device apparatus according to the present disclosure (hereinafter referred to as an "embodiment") with reference to the drawings. Note that the present disclosure is not limited to the embodiment. Furthermore, the embodiments can be appropriately combined within the scope of not causing any contradiction in the processing content. Furthermore, the same components in the following embodiments are given the same reference numerals, and redundant explanations will be omitted.

[0007] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision, installation precision, etc.

[0008] For ease of understanding, Fig. 1 illustrates a three-dimensional Cartesian coordinate system in which the arrangement directions of the superconducting device apparatus 100 (see Fig. 7) are the X-axis and Y-axis, respectively, and the direction intersecting the XY plane is the Z-axis. This Cartesian coordinate system is also shown in other drawings used in the following explanation. In the following explanation, for convenience, the positive side of the Z-axis may be referred to as "up."

[0009] Conventionally, packaging technologies for mounting superconducting elements such as Josephson devices have been known. The above-mentioned Patent Document 1 discloses a package for mounting superconducting elements, in which a superconducting element such as a Josephson device is mounted on a substrate having a conductor layer inserted between ceramic layers. To achieve a superconducting state, such superconducting elements are typically maintained in an atmosphere at a temperature lower than room temperature, for example, at approximately the boiling point of liquid nitrogen (77 K). However, the package disclosed in Patent Document 1 still has difficulty achieving high conductivity at high frequencies. Therefore, a technology for achieving high conductivity at high frequencies is desired.

[0010] First, a configuration example of a superconducting device 1 (package (PKG) in the present application) according to an embodiment will be described with reference to Figs. 1, 2, and 3. Fig. 1 is a perspective view schematically showing a configuration example of a superconducting device 1 according to an embodiment. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 3 is a perspective view schematically showing the arrangement of wiring conductors 14 on the second main surface 12 of a first substrate wiring layer 10.

[0011] The superconducting device 1 includes a laminate 2 having a first substrate wiring layer 10. The first substrate wiring layer 10 has a first main surface 11 and a second main surface 12 located on the opposite side of the first main surface 11. The first substrate wiring layer 10 has a first insulating layer 13 and conductors 14 to 19. The first insulating layer 13 is made of ceramic. In this embodiment, the laminate 2 has the first substrate wiring layer 10, the second substrate wiring layer 20, and the third substrate wiring layer 30, but the number of substrate wiring layers is not limited to three. The number of substrate wiring layers may be three or more, or may be two.

[0012] Of the conductors 14 to 19, the wire-shaped conductor 14 arranged along the second main surface 12 of the first insulating layer 13 in FIG. 1 may be a superconductor. In other words, the material of the wire-shaped conductor 14 arranged along the second main surface 12 of the first insulating layer 13 may be a conductive material that exhibits a superconducting state at a predetermined temperature. The predetermined temperature is a temperature lower than room temperature, for example, a temperature about the boiling point of liquid helium (4 K) or lower. Hereinafter, the wire-shaped conductor 14 may be referred to as the wiring conductor 14. The wiring conductor 14 refers to a conductor that has an elongated shape when viewed in a plan view.

[0013] Among the conductors 14 to 18, the film-like conductors 16 and 17 described below are conductors formed so as to occupy almost the entire main surface of an insulating layer such as the first insulating layer 13, or an area close to this. Hereinafter, the film-like conductors 16 and 17 may be referred to as solid conductors 16 and 17. The solid conductors 16 and 17 are generally used as power supply layers and ground layers in electric circuits. In Figure 2, the member designated by the reference numeral 7 is a protective film that protects the conductors 16 and 18 from scratches and corrosion.

[0014] Here, the second main surface 12 of the first insulating layer 13 is a smooth surface having a surface roughness Ra of 0.1 μm or less. A smooth surface may also be referred to as a flat surface. Alternatively, in the present disclosure, a surface having a surface roughness Ra of 0.1 μm or less is defined as a smooth surface or a flat surface.

[0015] Since the second main surface 12 of the ceramic first insulating layer 13 is a smooth surface with a small surface roughness Ra, the surface of the superconductor wiring conductor 14 formed on the second main surface 12 also has a small surface roughness Ra. This allows the superconducting device 1 to achieve high conductivity at high frequencies even with a shallow skin depth.

[0016] The material constituting the first insulating layer 13 is ceramic. The first insulating layer 13 may be a sintered body of ceramic particles. The first insulating layer 13 may have a structure in which a plurality of ceramic particles are bonded via grain boundaries. The first insulating layer 13 may have a structure in which a large number of ceramic particles are bonded three-dimensionally via grain boundaries. Here, "large number" means that the number of particles is so large that it is difficult to count even within a range that can be observed using an electron microscope. The particle size of the ceramic particles can be in the range of 0.1 μm to 10 μm.

[0017] The first insulating layer 13 is preferably dense. When the first insulating layer 13 is dense, the ceramic particles forming the first insulating layer 13 may be a mixture of ceramic particles with different particle sizes. When the ceramic particles are granular, particularly spherical, gaps will inevitably be formed between the ceramic particles. Therefore, the first insulating layer 13 preferably contains ceramic particles with a particle size small enough to fit into the gaps formed when larger ceramic particles come into contact with each other.

[0018] Furthermore, when the ceramic particles are granular, particularly spherical, there are portions where the ceramic particles are in point contact or in a state of contact close to point contact. In such cases, gaps also occur in areas other than the portions where the ceramic particles are in point contact. In such cases, it is preferable that the first insulating layer 13 contains a glass component (glass phase). Since the glass component tends to melt and become amorphous when the ceramic is fired, it can fill the gaps in areas other than the portions where the ceramic particles are in point contact.

[0019] The first insulating layer 13 preferably contains a plurality of ceramic particles of different particle sizes and a glass phase. The second main surface 12 of the first insulating layer 13 is preferably a polished surface of a ceramic sintered body. The polished surface exposes the internal cross sections of the ceramic particles. The polished surface tends to be a flat surface because there is almost no difference in the height of the cross sections of the ceramic particles. The state in which the internal cross sections of the ceramic particles are exposed has a higher uniformity of composition than the surface of the ceramic particles. The ceramic particles seen on the polished surface are in a state in which the outlines of the particles are in contact with each other. The fact that the outlines of the ceramic particles are visible means that the interiors of the ceramic particles are exposed. The second main surface 12 of the first insulating layer 13 has a high proportion of the main component and a low proportion of components other than the main component.

[0020] On the other hand, if the second main surface 12 of the first insulating layer 13 is in the state of the fired surface of the ceramic sintered body, it will be a continuous surface of the ceramic particle surface. If the ceramic sintered body is in the state of the fired surface, the surface shape of the granular ceramic particle will be revealed, causing waviness on the second main surface 12 of the first insulating layer 13. In addition, the surface of the ceramic particle has a high concentration of additive components, auxiliary components, etc., resulting in high compositional non-uniformity.

[0021] Next, a method for determining the surface roughness Ra will be described with reference to Figures 4 and 5. Figure 4 is a cross-sectional view schematically showing a laminated structure of the first insulating layer 13 of the first substrate wiring layer 10, the wiring conductor 14, and the second insulating layer 23 of the second substrate wiring layer 20. Figure 5 is a schematic diagram showing a method for determining the surface roughness Ra.

[0022] To determine the surface roughness Ra, the superconducting device 1 is first polished to expose its cross section. The exposed cross section shows the first substrate wiring layer 10 and the conductors 14-18 bonded together. In FIG. 4 , the second substrate wiring layer 20 is laminated on the wiring conductor 14. Here, the shape of the bonded surface between the first substrate wiring layer 10 and the conductors 14-18 is determined by tracing the path of the bonded surface. For convenience, the shape of the bonded surface between the first substrate wiring layer 10 and the conductors 14-18 is referred to as the shape of the bonded surface. The shape of the bonded surface is determined from a photograph of the cross section of the superconducting device 1 taken with a scanning electron microscope. The shape of the bonded surface may also be determined by image processing of the electron microscope photograph. Then, as shown in FIG. 5 , a reference length L is extracted from the roughness curve (shape of the bonded surface) in the direction of the mean line m to determine the surface roughness Ra. Specifically, the surface roughness Ra is determined using the following formula (1). In formula (1), L is the reference length.

[0023] Next, a configuration example of the superconducting device 1 according to the embodiment will be described in detail with reference to FIGS. 1, 2 and 3. FIG.

[0024] In such a superconducting device 1, the first insulating layer 13 may have both the first principal surface 11 and the second principal surface 12 as smooth surfaces, and may have superconductor wiring conductors 14, 15 on both principal surfaces.

[0025] This allows the superconducting device 1 to have high conductivity on both sides of the first substrate wiring layer 10. It is preferable that the first insulating layer 13 has a first main surface 11, which is located opposite the second main surface 12, as a polished surface, similar to the second main surface 12. In this case, it is preferable that a superconductor wiring conductor 15 is also disposed on the first main surface 11. The first main surface 11 may have a film-like conductor 16 disposed around the wiring conductor 15 at a position spaced apart from the wiring conductor 15. "Spaced apart from the conductor" means that the wiring conductor 15 is electrically insulated. It is also preferable that the second main surface 12 has a film-like conductor 17 disposed around the wiring conductor 14 at a position spaced apart from the wiring conductor 14.

[0026] The film-like conductor 16 is arranged around the wiring conductor 14 on the first main surface 11 at a distance from the conductor because this arrangement makes it possible to increase the transmission efficiency of electromagnetic waves using the film-like conductor 16. The same effect can be achieved by arranging the film-like conductor 17 around the wiring conductor 14 on the second main surface 12 at a distance from the wiring conductor 14. If the material of the film-like conductors 16, 17 is a superconductor, the film-like conductors 16, 17 will exhibit the Meissner effect, which is one of the properties of superconductors, at low temperatures. This also makes it possible to form a stronger magnetic shield.

[0027] The material of the first insulating layer 13 only needs to be insulating at the temperature at which the superconducting device 1 is used. For example, even if the electrical resistance of the material of the first insulating layer 13 is semiconducting at room temperature (25° C.), it only needs to be insulating at a lower temperature at which the superconducting device 1 is used. The surface roughness Ra of the first main surface 11 of the first insulating layer 13 is preferably 0.1 μm or less.

[0028] In such a superconducting device 1, it is more preferable that the surface roughness Ra of the smooth surface of the first insulating layer 13 is 0.05 μm or less.

[0029] This can further increase the high frequency conductivity of the first substrate wiring layer 10 in the superconducting device 1. In particular, it is possible to reduce losses due to the conductor portion. In this case, it is preferable that the surface roughness Ra of both the first main surface 11 and the second main surface 12 (smooth surfaces) is 0.05 μm or less.

[0030] In such a superconducting device 1, the laminate 2 may have a second substrate wiring layer 20 overlapping the first substrate wiring layer 10. The second substrate wiring layer 20 may have a third main surface 21 and a fourth main surface 22 located on the opposite side thereof. In the laminate 2 constituting the superconducting device 1, the wiring conductor 14 arranged on the second main surface 12 of the first substrate wiring layer 10, which is located on the inner layer side, may abut against the third main surface 21 of the second substrate wiring layer 20.

[0031] The laminate 2 constituting the superconducting device 1 is configured to include a superconductor wiring conductor 14 in an inner layer of the laminate 2, and therefore high conductivity can be imparted even to the inner layer of the superconducting device 1. The superconducting device 1 is also configured such that the first substrate wiring layer 10 is disposed on the second substrate wiring layer 20. Therefore, even if the thermal expansion coefficients of the second substrate wiring layer 20 and the first substrate wiring layer 10 differ, the superconducting device 1 can maintain its strength because the first insulating layer 13 constituting the first substrate wiring layer 10 is made of ceramic and has a high Young's modulus.

[0032] In the superconducting device 1, the superconducting elements 40 can be arranged at positions spaced apart from the first substrate wiring layer 10 and the second substrate wiring layer 20 (see FIG. 8 ). Therefore, the superconducting device 1 can reduce the load (stress concentration) on the superconducting elements 40 even when distortion occurs in the superconducting device 1 due to the thermal expansion coefficient.

[0033] In such a superconducting device 1, the second insulating layer 23 may be made of an organic resin. In the superconducting device 1, an insulating layer made of an organic resin having a lower Young's modulus than the first insulating layer 13 is laminated on the first insulating layer 13 made of ceramic, and therefore, stress generated between the first substrate wiring layer 10 and the second substrate wiring layer 20 can be absorbed and alleviated on the second substrate wiring layer 20 side. This allows the superconducting device 1 to achieve high durability.

[0034] When the superconducting device 1 has an insulating layer made of organic resin, the Young's modulus of the entire superconducting device 1 can be reduced, thereby reducing the occurrence of cracks. In the superconducting device 1, the organic resin insulating layer and the ceramic insulating layer are directly bonded to each other over the entire main surfaces of the respective layers. This allows the superconducting device 1 to increase the binding force between the two layers. Furthermore, the superconducting device 1 can increase the thermal conductivity between the two layers. Therefore, in the superconducting device 1, the laminate 2 of the first substrate wiring layer 10 having a ceramic insulating layer and the second substrate wiring layer 20 having an organic resin insulating layer can use the inherent physical properties of each layer as a binding force even in an environment where the temperature changes rapidly.

[0035] In such a superconducting device 1, the second substrate wiring layer 20 may have a second insulating layer 23. Of the two main surfaces of the second insulating layer 23, at least a third main surface 21 may have a surface roughness Ra of 0.3 μm or less.

[0036] In the superconducting device 1, the second substrate wiring layer 20 abuts on the first substrate wiring layer 10 having the superconductor wiring conductor 14, and the second insulating layer 23 constituting the second substrate wiring layer 20 has a small surface roughness. This allows the superconductor wiring conductor 14 of the first substrate wiring layer 10 to have a small skin depth on both sides of the wiring conductor 14 within the inner layer of the laminate 2.

[0037] In such a superconducting device 1, the material constituting the first insulating layer 13 may be alumina ceramics or sapphire.

[0038] Alumina ceramics have a relative dielectric constant of 8 to 10, which is close to that of silicon (relative dielectric constant 11 to 12) or sapphire (relative dielectric constant 9 to 10), which are materials from which the superconducting element 40 (see FIG. 8) is formed. As a result, when the material constituting the first insulating layer 13 of the superconducting device 1 is alumina ceramics, the size and pitch of the terminals located on the alumina ceramics and silicon, or the size and pitch of the terminals located on the alumina ceramics and sapphire, can be made equivalent. This makes it easier to achieve impedance matching in the superconducting device 1. Furthermore, when the material constituting the first insulating layer 13 of the superconducting device 1 is sapphire, impedance matching can be easily achieved in the same way as when the material constituting the first insulating layer 13 is alumina ceramics.

[0039] In such a superconducting device 1, the first substrate wiring layer 10 may have superconductor film-like conductors 16, 17 around the wiring conductors 14, 15, spaced apart from the wiring conductors 14, 15. In this case, the superconductor film-like conductors 16, 17 may form strip lines between the wiring conductors 14, 15, which are superconductors arranged on the same main surface of the first substrate wiring layer 10.

[0040] As a result, the superconducting device 1 can configure wiring with smaller radiation loss, and with smaller resistance and smaller conductor loss due to the use of a superconductor for the signal line.

[0041] In such a superconducting device 1, the first insulating layer 13 may further have superconducting film-like conductors 16, 17 around each of the superconducting wiring conductors 14, 15 arranged on both main surfaces of the first insulating layer 13.

[0042] The superconducting device 1 can have a stripline structure on both sides of the first substrate wiring layer 10. This allows the superconducting device 1 to have smaller radiation loss, and by using a superconductor for the signal line, the resistance is small, resulting in wiring with smaller conductor loss.

[0043] In the superconducting device 1, the second substrate wiring layer 20 may have via conductors 29. The via conductors 29 may be made of a normal conductor material. The via conductors 29 may protrude from the third main surface 21 and the fourth main surface 22 of the second insulating layer 23 when the second substrate wiring layer 20 is overlaid on the first substrate wiring layer 10.

[0044] Furthermore, the superconductor wiring conductors 14, 15 formed on the first substrate wiring layer 10 preferably protrude from the first main surface 11 and the second main surface 12 of the first insulating layer 13. The superconductor wiring conductors 14, 15 protruding from the first main surface 11 and the second main surface 12 of the first insulating layer 13 means that the wiring conductors 14, 15 are elevated by a predetermined thickness from the main surface of the first insulating layer 13. In other words, the wiring conductors 14, 15 are arranged so as to have a step from the main surface of the first insulating layer 13 by that thickness. Because the superconductor conductor protrudes from the main surface of the first substrate wiring layer 10 by that thickness, when the second substrate wiring layer 20 is laminated on the first substrate wiring layer 10, the superconductor conductor on the first substrate wiring layer 10 side is formed so as to be embedded in the second insulating layer 23 constituting the second substrate wiring layer 20.

[0045] The via conductors 29 formed in the second substrate wiring layer 20 are subjected to pressure from the superconductor wiring conductors 14 of the first substrate wiring layer 10, and their lengths are shortened by the thickness of the superconductor wiring conductors 14. The via conductors 29 formed in the second substrate wiring layer 20 become densified. At the same time, the bond between the via conductors 29 formed in the second substrate wiring layer 20 and the superconductor wiring conductors 14 of the first substrate wiring layer 10 also becomes stronger. Furthermore, the electrical connection between the first substrate wiring layer 10 and the second substrate wiring layer 20 becomes stronger, improving connection reliability.

[0046] In such a superconducting device 1, the laminate 2 may have a through-hole 6 in the center when viewed from above. The through-hole 6 serves as a housing portion for housing a superconducting element 40 (see FIG. 8).

[0047] The superconducting device 1 has a package structure that makes it difficult for the superconducting element 40 to come into contact with the superconducting device 1, which makes it possible to reduce mutual thermal influence between the superconducting element 40 and the superconducting device 1. This leads to stabilization of the oscillation function of the superconducting element 40. Furthermore, the transmission characteristics of the superconducting device 1 tend to be stabilized.

[0048] Next, another embodiment of the superconducting device 1 will be described with reference to Fig. 6. Fig. 6 is a cross-sectional schematic view showing another embodiment of the superconducting device 1.

[0049] The through-hole 6 may have a flush inner wall between the first substrate wiring layer 10 and the second substrate wiring layer 20, or may have a step between the first substrate wiring layer 10 and the second substrate wiring layer 20. For example, as shown in Fig. 6 , the superconducting device 1 may have a structure in which the opening diameter differs between the first substrate wiring layer 10 and the second substrate wiring layer 20, and has a step portion 8.

[0050] This makes it easier to fix the stage member 50 (see FIG. 8 ) to the through-hole 6 in the second substrate wiring layer 20, which has a smaller opening diameter. Furthermore, in the superconducting device 1, the through-hole 6 in the first substrate wiring layer 10, which has a larger opening diameter, makes it less likely that the inner wall of the first substrate wiring layer 10 will come into contact with the upper part of the stage member 50 and the superconducting element 40 (see FIG. 8 ) mounted thereon. Furthermore, in the superconducting device 1, it is easier to stabilize the oscillation function of the superconducting element 40 and the transmission characteristics of the superconducting device 1 between the first substrate wiring layer 10 and the stage member 50 and the superconducting element 40. Note that the opening diameter of the first substrate wiring layer 10 in the superconducting device 1 may be smaller than the opening diameter of the second substrate wiring layer 20.

[0051] Next, a configuration example of the superconducting device 100 according to the embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a perspective view schematically showing the configuration example of the superconducting device 100 according to the embodiment. Fig. 8 is a cross-sectional view taken along line BB in Fig. 7.

[0052] The superconducting device apparatus 100 is a combination of any of the above-described superconducting devices 1 and a stage member 50. The stage member 50 may have a base portion 51 and a pillar portion 52. The base portion 51 may be flat. The pillar portion 52 may be located in the center of the base portion 51 and protrude from the surface of the base portion 51. The pillar portion 52 may be inserted into the through-hole 6 of the laminate 2 that constitutes the superconducting device 1. The stage member 50 may have an upper surface of the pillar portion 52 that serves as a mounting portion for mounting the superconducting element 40.

[0053] The superconducting device apparatus 100 can be configured so that the superconducting elements 40 are placed on the pillars 52 of the stage member 50, resulting in a package structure in which the superconducting elements 40 are less likely to come into contact with the superconducting device apparatus 100. This makes it possible for the superconducting device apparatus 100 to reduce the mutual thermal influence between the superconducting device 1 and the superconducting elements 40. Furthermore, the superconducting device apparatus 100 makes it possible for the stage member 50 to exhaust heat from the superconducting elements 40.

[0054] The stage member 50 is preferably formed from a metal material. The metal material of the stage member 50 is preferably one selected from the group consisting of aluminum, copper, silver, and stainless steel. The base portion 51 and the column portion 52 of the stage member 50 are preferably formed integrally. The stage member 50 is preferably formed integrally by cutting out an original metal ingot.

[0055] The superconducting element 40 may be joined to the mounting portion of the column 52 by a joining material. The joining material may be metallic or conductive resin-based. The metallic joining material is preferably one selected from the group consisting of solder (In, Sn—Ag, Pb—Sn), Au—Sn, silver brazing, and wood metal. For solder, In is preferred because it exhibits little change in density even at extremely low temperatures. For conductive resin-based joining materials, for example, those containing epoxy resin as the main component are preferred.

[0056] The base portion 51 may be configured to be larger in area than the superconducting device 1 or the insulating layers (first insulating layer 13, second insulating layer 23, third insulating layer 33) that constitute the superconducting device 1. If the base portion 51 of the superconducting device apparatus 100 is larger in area than the superconducting device 1 or the insulating layers (first insulating layer 13, second insulating layer 23, third insulating layer 33) that constitute the superconducting device 1, the superconducting device 1 is less likely to come into contact with surrounding members, thereby preventing malfunctions in the superconducting device 1. The superconducting device 1 and the stage member 50 may be bonded (joined) using the same bonding material that is used to bond the stage member 50 and the superconducting element 40.

[0057] Next, other configuration examples of the superconducting device 100 according to the embodiment will be described.

[0058] The superconducting device apparatus 100 is connected to an external circuit (not shown) for driving the superconducting elements 40. The external circuit is placed outside the system of the superconducting device apparatus 100. The ambient temperature around the external circuit is room temperature, about 25°C.

[0059] In this superconducting device 1, the thickness of the first substrate wiring layer 10 may be greater than the thickness of the second substrate wiring layer 20. In other words, the thickness of the first insulating layer 13 made of ceramic may be greater than the thickness of the second insulating layer 23 made of organic resin. With this configuration, the thickness of the first insulating layer 13 made of ceramic is greater than the thickness of the second insulating layer 23 made of organic resin, making the laminate 2 less likely to deform. In this case, the superconducting device 100 has a small overall thermal expansion coefficient because the second insulating layer 23 made of organic resin is thin. Therefore, the superconducting device 100 can reduce the load (stress) on the superconducting elements 40, leading to improved mechanical reliability.

[0060] The first substrate wiring layer 10 may have a via conductor (first via conductor 19). When superconducting conductors are arranged on the first main surface 11 and the second main surface 12 of the first substrate wiring layer 10, the first via conductor 19 can electrically connect the superconducting conductors arranged on the first main surface 11 and the second main surface 12, respectively. In this case, it is preferable that the first via conductor 19 is also a superconductor. The second substrate wiring layer 20 may also have a via conductor (second via conductor 29). In this case, the second via conductor 29 may be a superconductor. The superconductor material is preferably at least one of mercury, vanadium, lead, niobium, niobium-titanium, niobium-tin, niobium-aluminum, vanadium-gallium, and magnesium-boron.

[0061] As a result, the superconducting device apparatus 100 can reduce noise without resistance at cryogenic temperatures by having the superconducting via conductors 19, 29. Furthermore, the superconducting device apparatus 100 can reduce the inductance of the circuit in the superconducting device 1 by using the superconducting solid conductors 16, 17 as the ground layer and power supply layer.

[0062] In the above-described embodiment, an example has been described in which the superconducting device 1 has the superconducting element 40, but the elements mounted on the superconducting device apparatus 100 are not limited to this. For example, the superconducting device 100 may have quantum elements such as Josephson elements, silicon quantum bit elements, ion trap elements, and optical elements.

[0063] Next, a method for fabricating the superconducting device 100 will be described.

[0064] A specific superconducting device 100 was fabricated as follows. To fabricate the above-described superconducting device 1, first, a first substrate precursor was fabricated to become the first substrate wiring layer 10. For example, a ceramic substrate made of alumina (referred to as an alumina ceramic substrate) was prepared.

[0065] Next, the alumina ceramic substrate was subjected to a polishing treatment. The thickness of the alumina ceramic substrate was 0.3 mm. The surface roughness Ra of the polished alumina ceramic substrate was 0.05 μm on both sides.

[0066] Next, through holes 6 were formed in the polished substrate using a laser processing machine. Next, a lead (Pb) superconducting film was formed on the surface of the substrate with the polished through holes 6 formed thereon and in the through holes 6 by electron beam evaporation. During film formation, the alumina ceramic substrate was cleaned using argon (Ar) gas. After this, exposure, development, and etching processes were performed to form wiring conductors 14, 15 and via conductors 19 as shown in FIGS. 1 and 3 . Note that solid conductors 16, 17 were left around the wiring conductors 14, 15. The solid conductors 16, 17 were spaced apart from the wiring conductors 14, 15, respectively.

[0067] On the other hand, a second substrate precursor that would become the second substrate wiring layer 20 was prepared. First, an uncured organic resin sheet containing silica powder in epoxy resin was prepared. The thickness of the organic resin sheet was 0.2 μm. The amount of silica powder added was 150 parts by mass per 100 parts by mass of the epoxy resin.

[0068] Next, through holes 6 were formed in the organic resin sheet using a laser processing machine. Next, the through holes 6 of the organic resin sheet with the through holes 6 formed therein were filled with a conductive paste. The conductive paste contains copper powder as the main material and a low-melting-point metal powder. The low-melting-point metal powder is powder of Sn, Bi, or the like. The conductive paste is composed of 50 mol % copper powder, 25 mol % Sn powder, 25 mol % Bi powder, and the remainder being epoxy resin.

[0069] Next, a copper foil pattern was attached to the surface of the organic resin sheet, which had the through holes 6 filled with the conductive paste, that would become the fourth main surface 22. The copper foil pattern had wiring conductors 28 and a solid conductor around them. In this experiment, no copper foil pattern was attached to the third main surface 21.

[0070] Next, a second substrate precursor was laminated on the second main surface 12 of the first substrate precursor. First, a copper foil pattern was attached to the fourth main surface 22 of the organic resin sheet. The thickness of the copper foil was 9 μm. The copper foil was prepared by attaching a PET film to the matte surface, which was the back surface opposite to the main surface. Hereinafter, the copper foil film will be referred to as a copper foil film, in which unpatterned copper foil is attached to a PET film. The surface roughness Ra of the shiny surface, which was the main surface of the copper foil, was 0.25 μm.

[0071] Next, the copper foil film was subjected to exposure, development, and etching treatments to produce a copper foil pattern film having a copper foil pattern patterned on a PET film. The copper foil pattern film was attached to the main surface of the organic resin sheet by a transfer method to produce a laminate of the organic resin sheet and the copper foil pattern film. Specifically, the copper foil pattern film was laminated on the organic resin sheet so that the main surface of the copper foil was adhered to the main surface of the organic resin sheet, and the PET film was peeled off from the back surface of the copper foil. The copper foil pattern film was laminated on the organic resin sheet at a pre-lamination temperature of 25°C and a pre-lamination pressure of 40 kgf / cm. ２ , main lamination temperature: 50°C, and main lamination pressure: 70 kgf / cm ２ The experiment was carried out under the conditions of

[0072] Next, the main surface (third main surface 21) of the second substrate precursor, on which the copper foil pattern was not attached, was laminated on the second main surface 12 of the first substrate precursor, and another layer of organic resin sheet was laminated thereon, followed by a pressurized and heated treatment to produce a base laminate. Pressurized and heated treatment (250°C, 10 MPa, 15 seconds) was performed using a laminator used in the manufacture of organic substrates.

[0073] Next, the portion that would become the second substrate wiring layer 20 was cut from the base laminate after lamination so as to remove the portion that protruded beyond the size of the first substrate wiring layer 10. In this way, a sample 1 that would become the superconducting device 1 disclosed above was obtained.

[0074] Sample 2 was fabricated as a comparative example using the same process, except that an unpolished alumina ceramic substrate (surface roughness Ra = 0.5 μm) was used as the first insulating layer 13 of the first substrate wiring layer 10. The dimensions of Samples 1 and 2 were 45 mm × 45 mm × 0.65 mm. Separately, a stage member 50 having the structure shown in FIGS. 7 and 8 was prepared. The stage member 50 was made of copper. The shape and size of the stage member 50 corresponded to the structure of the superconducting device 100 shown in FIGS. 7 and 8.

[0075] For the evaluation of the characteristics of Sample 1 and Sample 2, the following samples corresponding to the fabricated first substrate wiring layer 10 were separately prepared and the interfacial conductivity was evaluated at room temperature. The measured values ​​of the interfacial conductivity at room temperature show a similar tendency even at low temperatures at which the superconducting device 1 functions. The evaluation samples here correspond to Sample 1A for Sample 1, and to Sample 2A for Sample 2, which is a comparative example.

[0076] Sample 1A was fabricated as follows. A polished alumina ceramic was prepared as the first insulating layer 13 constituting the first substrate wiring layer 10. The interfacial conductivity was measured using the dielectric cylindrical resonator method described below. The measurement sample used was a 50 mm diameter sample with conductors formed over almost the entire surface of both sides. Pb (lead) was used as the conductor. For the comparative example (Sample 2A), an alumina ceramic that had not been polished was used. The alumina ceramic substrate used had an alumina ratio of 97%. The conductor was formed by sputtering.

[0077] The following evaluations were carried out. The method for measuring interfacial conductivity using the dielectric rod resonator method is a method for measuring the conductivity at the interface between the conductor and the insulating layer, i.e., the conductor interface, by attaching an insulating layer with the conductor formed inside to both end faces or one end face of a dielectric rod made of a dielectric material with known relative permittivity and dielectric loss in a predetermined relationship to form a dielectric resonator.

[0078] The principle of this measurement method is that when an electromagnetic resonator is constructed by sandwiching a conductor plate (usually a conductor plate having a diameter D about three times the diameter d of the dielectric cylinder) that is large enough to ignore the edge effect, parallel to both end faces of a dielectric cylinder having a predetermined dimensional ratio (height h / diameter d), the high-frequency current flowing in the conductor plate due to the TEomn resonance mode (hereinafter referred to as the TEomn mode) is distributed only on the short-circuit surface, i.e., the opposing surface between the dielectric and the conductor.

[0079] In a dielectric resonator, the high-frequency current flowing through the conductor due to the TEomn mode (m = 1, 2, 3 ..., n = 1, 2, 3 ...) is distributed only at the interface between the conductor and the dielectric substrate in contact with the dielectric cylinder. By utilizing this, the interfacial conductivity can be calculated from the measured resonant frequency f0 of the TEomn mode (m = 1, 2, 3 ..., n = 1, 2, 3 ...) and the unloaded Q and Qu. The interfacial conductivity was measured at a frequency of 2 GHz. When the interfacial conductivity of Sample 1A was normalized to that of Sample 2A, which is 1, the interfacial conductivity was about 1.5 times higher.

[0080] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0081] The present technology can also be configured as follows: (1) A superconducting device including a laminate having a first substrate wiring layer, wherein the first substrate wiring layer has a first main surface and a second main surface opposite to the first main surface, and has a first insulating layer and a conductor, the first insulating layer being made of ceramic, wherein a wire-like conductor arranged along one of the two main surfaces of the first insulating layer is a superconductor, and one of the two main surfaces of the first insulating layer is a smooth surface having a surface roughness Ra of 0.1 μm or less. (2) The superconducting device according to (1), wherein the laminate has a second substrate wiring layer overlapping the first substrate wiring layer, wherein the second substrate wiring layer has a third main surface and a fourth main surface opposite to the third main surface, and the wire-like conductor of the superconductor arranged on the second main surface of the first substrate wiring layer abuts the third main surface of the second substrate wiring layer. (3) The superconducting device according to (1) or (2), wherein both the first and second main surfaces of the first insulating layer are smooth surfaces and the first insulating layer has a wiring-like conductor of the superconductor on both main surfaces. (4) The superconducting device according to any one of (1) to (3), wherein the smooth surfaces of the first insulating layer have a surface roughness Ra of 0.05 μm or less. (5) The superconducting device according to (2), wherein the second substrate wiring layer has a second insulating layer, and wherein at least the third main surface of the two main surfaces of the second insulating layer has a surface roughness Ra of 0.3 μm or less. (6) The superconducting device according to (5), wherein the second insulating layer is made of an organic resin, and wherein the Young's modulus of the second insulating layer is lower than the Young's modulus of the first insulating layer. (7) The superconducting device according to any one of (1) to (6), wherein the material constituting the first insulating layer is alumina ceramics or sapphire. (8) The superconducting device according to any one of (1) to (7), wherein the first substrate wiring layer has a superconductor film-like conductor around the superconductor wire-like conductor and spaced apart from the superconductor wire-like conductor. (9) The superconducting device according to (3), wherein the first insulating layer further has a superconductor film-like conductor around each of the superconductor wire-like conductors arranged on both main surfaces.(10) A superconducting device according to any one of (1) to (9), wherein the laminate has a through-hole in a central portion in a plan view, the through-hole serving as a storage portion for a superconducting element. (11) A superconducting device apparatus comprising the superconducting device according to (10) and a stage member, wherein the central portion of the stage member serves as a mounting portion for mounting the superconducting element. (12) The superconducting device apparatus according to (11), wherein the stage member has a base portion and a pillar portion, the base portion is flat, the pillar portion is located in the center of the base portion, protrudes from the surface of the base portion and is inserted into the through-hole of the superconducting device, and the upper surface of the pillar portion serves as the mounting portion for mounting the superconducting element.

[0082] REFERENCE SIGNS LIST 1 superconducting device 2 laminate 6 through hole 10 first substrate wiring layer 11 first main surface 12 second main surface 13 first insulating layer 14 wiring conductor 16 film-like conductor (solid conductor) 17 film-like conductor (solid conductor) 20 second substrate wiring layer 21 third main surface 22 fourth main surface 23 second insulating layer 40 superconducting element 50 stage member 51 base portion 52 column portion

Claims

1. A superconducting device comprising a laminate having a first substrate wiring layer, wherein the first substrate wiring layer has a first main surface and a second main surface located opposite the first main surface, and also has a first insulating layer and a conductor, the first insulating layer being made of ceramic, wherein a wiring-like conductor arranged along one of the two main surfaces of the first insulating layer is a superconductor, and one of the two main surfaces of the first insulating layer is a smooth surface with a surface roughness Ra of 0.1 μm or less.

2. A superconducting device as described in claim 1, wherein the laminate has a second substrate wiring layer overlapping the first substrate wiring layer, the second substrate wiring layer has a third main surface and a fourth main surface located opposite the third main surface, and the wire-shaped conductor of the superconductor arranged on the second main surface of the first substrate wiring layer abuts the third main surface of the second substrate wiring layer.

3. A superconducting device as described in claim 1 or claim 2, wherein both the first and second main surfaces of the first insulating layer are smooth surfaces and have superconductor wiring-like conductors on both main surfaces.

4. A superconducting device according to any one of claims 1 to 3, wherein the smooth surface of the first insulating layer has a surface roughness Ra of 0.05 μm or less.

5. A superconducting device as described in claim 2, wherein the second substrate wiring layer has a second insulating layer, and the surface roughness Ra of at least the third main surface of the two main surfaces of the second insulating layer is 0.3 μm or less.

6. The superconducting device according to claim 5, wherein the second insulating layer is made of an organic resin, and the Young's modulus of the second insulating layer is lower than the Young's modulus of the first insulating layer.

7. A superconducting device according to any one of claims 1 to 6, wherein the material constituting the first insulating layer is alumina ceramics or sapphire.

8. A superconducting device according to any one of claims 1 to 7, wherein the first substrate wiring layer has a film-like conductor of superconductor around the wire-like conductor of superconductor, spaced apart from the wire-like conductor of superconductor.

9. A superconducting device according to claim 3, wherein the first insulating layer further has a superconducting film-like conductor around each of the wire-like conductors of the superconductor arranged on both of the main surfaces.

10. A superconducting device according to any one of claims 1 to 9, wherein the laminate has a through hole in the center in a plan view, the through hole serving as a housing portion for housing a superconducting element.

11. A superconducting device apparatus comprising the superconducting device according to claim 10 and a stage member, the central portion of said stage member being a mounting portion for mounting said superconducting element.

12. A superconducting device apparatus as described in claim 11, wherein the stage member has a base portion and a pillar portion, the base portion is flat, the pillar portion is located at the center of the base portion, protrudes from the surface of the base portion, and is inserted into a through-hole of the superconducting device, and the upper surface of the pillar portion serves as a mounting portion for mounting the superconducting element.

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