Method for manufacturing Josephson junction device and method for manufacturing quantum bit

Abstract

This method for manufacturing a Josephson junction element comprises: a step for forming a mask layer on a substrate; a step for forming a first superconductive film on the substrate through first film formation from a first oblique direction, using the mask layer as a mask; a step for forming an insulating film on the surface of the first superconductive film; and a step for forming a second superconductive film having a region that overlaps the first superconductive film with the insulating film interposed therebetween through second film formation from a second oblique direction, using the mask layer as a mask. The step for forming the mask layer includes forming a mask layer having a first mask pattern that is positioned in a first region of the substrate and includes a first opening extending along the incidence direction of the film-forming material used in one of the first and second film formations and a second opening extending in a direction intersecting the first opening, and a second mask pattern that is positioned in a second region of the substrate and includes a third opening extending inclined relative to the first opening along the incidence direction of the film-forming material used in the one film formation and a fourth opening extending in a direction intersecting the third opening, the second region being positioned closer to an end portion of the substrate than the first region.　

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a Josephson junction device and a method for manufacturing a quantum bit. [Background technology]

[0002] A quantum bit is known that includes a transmon in which a Josephson junction element and a capacitor are connected in parallel. The Josephson junction element has a structure in which an insulating film is sandwiched between two layers of superconducting film. The superconducting film is known to be formed by film deposition from an oblique direction (e.g., Patent Documents 1 and 2).

[0003] When forming a superconducting film by oblique deposition (e.g., oblique evaporation), differences in the angle of incidence of the film-forming material into the openings in the mask layer can cause differences in the width of the superconducting film within the substrate. Therefore, it is known that by correcting the width of the openings in the mask layer, the width of the superconducting film within the substrate can be made approximately the same even when the angle of incidence of the film-forming material into the openings in the mask layer is different (e.g., Patent Document 3). It is also known that by using a mask close to the wafer and moving the substrate while keeping the angle of incidence of the film-forming material into the openings in the mask constant, the width of the superconducting film within the substrate can be made approximately the same (e.g., Patent Document 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-243626 [Patent Document 2] U.S. Patent No. 4,256,816 [Patent Document 3] Special Publication No. 2021-503171 [Patent Document 4] U.S. Patent Application Publication No. 2021 / 0135085 Summary of the Invention [Problem to be solved by the invention]

[0005] The method of correcting the width of the opening in the mask layer as described in Patent Document 3 leaves room for improvement in terms of suppressing variations in the width of the superconducting film within the substrate.The method of moving the substrate while using a mask to keep the angle of incidence of the film-forming material constant as described in Patent Document 4 requires special equipment.

[0006] One aspect of the invention is to reduce the variation in the width dimension of the superconducting film within the substrate, thereby reducing the variation in the area of the Josephson junction. [Means for solving the problem]

[0007] In one aspect, the method includes the steps of: forming a mask layer on a substrate; depositing a first superconducting film on the substrate by first deposition from a first oblique direction using the mask layer as a mask; forming an insulating film on a surface of the first superconducting film; and depositing a second superconducting film having a region overlapping the first superconducting film via the insulating film by second deposition from a second oblique direction different from the first oblique direction using the mask layer as a mask. and a first mask pattern including a first opening extending along the incident direction of the film-forming material in one of the second film-forming processes and a second opening extending in a direction intersecting the first opening; and a second mask pattern located in a second region of the substrate and including a third opening extending obliquely with respect to the first opening along the incident direction of the film-forming material in the one of the second film-forming processes and a fourth opening extending in a direction intersecting the third opening, wherein the mask layer is formed so that the second region is closer to an edge of the substrate than the first region.

[0008] In one embodiment, a method for fabricating a Josephson junction element includes the steps of: forming a mask layer on a substrate; depositing a first superconducting film on the substrate by a first deposition process from a first oblique direction using the mask layer as a mask; forming an insulating film on a surface of the first superconducting film; and depositing a second superconducting film having a region overlapping the first superconducting film via the insulating film by a second deposition process from a second oblique direction different from the first oblique direction using the mask layer as a mask. and forming a mask layer having: a first mask pattern located in a first region of the substrate, the first mask pattern including a first opening extending along a direction of incidence of a film-forming material in one of the first and second film-forming processes and a second opening extending in a direction intersecting the first opening; and a second mask pattern located in a second region of the substrate, the second mask pattern including a third opening extending obliquely with respect to the first opening along a direction of incidence of a film-forming material in the one of the film-forming processes and a fourth opening extending in a direction intersecting the third opening, the second region being closer to an edge of the substrate than the first region. [Effects of the Invention]

[0009] As one aspect, the variation in the width dimension of the superconducting film within the substrate can be reduced, and the variation in the area of the Josephson junction can be reduced. [Brief explanation of the drawings]

[0010] [Figure 1] 1(a) to 1(c) are diagrams (part 1) showing a method for manufacturing a Dolan Bridge type Josephson junction device. [Figure 2] 2(a) and 2(b) are diagrams (part 2) showing a method for manufacturing a Dolan Bridge type Josephson junction device. [Figure 3]3(a) and 3(b) are diagrams showing the formation of a superconducting film on a wafer-shaped substrate by oblique vacuum deposition in a Dolan Bridge type Josephson junction device. [Figure 4] 4(a) to 4(c) are diagrams showing the incidence angles of the deposition material onto the mask patterns in the regions A to C of FIG. 3(a) and FIG. 3(b). [Figure 5] 5(a) to 5(c) are diagrams showing Josephson junction devices formed in regions A to C in FIGS. 3(a) and 3(b). [Figure 6] 6(a) to 6(c) are plan views (part 1) showing a method for manufacturing a Josephson junction device according to the first embodiment. [Figure 7] 7(a) to 7(c) are plan views (part 2) showing the method for manufacturing the Josephson device according to the first embodiment. [Figure 8] 8(a) to 8(c) are plan views (part 3) showing the method for manufacturing the Josephson device according to the first embodiment. [Figure 9] 9(a) to 9(c) are plan views (part 4) illustrating the method for manufacturing the Josephson device according to the first embodiment. [Figure 10] 10(a) to 10(c) are plan views (part 5) illustrating a method for manufacturing a Josephson device according to the first embodiment. [Figure 11] 11(a) to 11(c) are diagrams (part 1) showing a method for manufacturing a Manhattan-type Josephson junction device. [Figure 12] 12(a) and 12(b) are diagrams (part 2) showing a method for manufacturing a Manhattan-type Josephson junction device. [Figure 13] 13(a) and 13(b) are diagrams showing the formation of a superconducting film on a wafer-shaped substrate by oblique vacuum deposition in a Manhattan-type Josephson junction device. [Figure 14]14(a) to 14(i) are diagrams showing the incidence angles of the deposition material onto the mask patterns in the regions A to I of FIGS. 13(a) and 13(b). [Figure 15] 15(a) to 15(i) are diagrams showing Josephson junction devices formed in regions A to I of FIG. 13(a) and FIG. 13(b). [Figure 16] 16(a) to 16(i) are plan views (part 1) showing a method for manufacturing a Josephson device according to the second embodiment. [Figure 17] 17(a) to 17(i) are plan views (part 2) showing a method for manufacturing a Josephson junction device according to the second embodiment. [Figure 18] 18(a) to 18(i) are plan views (part 3) showing a method for manufacturing a Josephson junction device according to the second embodiment. [Figure 19] 19(a) to 19(i) are plan views (part 4) showing a method for manufacturing a Josephson device according to the second embodiment. [Figure 20] 20(a) to 20(i) are plan views (part 5) showing a method for manufacturing a Josephson device according to the second embodiment. [Figure 21] FIG. 21 is a plan view of a model used to examine the correlation between the crossing angle of the superconducting films and the area of the Josephson junction. [Figure 22] FIG. 22 is a circuit diagram of a quantum bit according to the third embodiment. [Figure 23] 23(a) and 23(b) are plan views showing a quantum bit according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [Example]

[0012] In Example 1, a Dolan Bridge Josephson device will be described. FIGS. 1(a) to 2(b) are diagrams illustrating a manufacturing method for a Dolan Bridge Josephson device. The upper figures in FIGS. 1(a) to 2(b) are plan views illustrating the manufacturing method for a Dolan Bridge Josephson device, and the lower figures are cross-sectional views taken along the line AA of the upper figures. The normal direction to the upper surface of the substrate 10 is defined as the Z-axis, and the directions perpendicular to each other in the planar direction of the upper surface of the substrate 10 are defined as the X-axis and Y-axis directions. In the upper plan views in FIGS. 1(b) to 2(b), the superconducting film 14, insulating film 16, and superconducting film 18 formed in the void 26 are hatched for clarity.

[0013] As shown in FIG. 1(a), a mask layer 12 is formed on a substrate 10. The mask layer 12 has an upper layer 12a and a lower layer 12b. A mask pattern 20 including an opening 22, an opening 24, and a void 26 is formed in the mask layer 12. The opening 22 extends in the X-axis direction, and the opening 24 extends in the Y-axis direction, and both are formed in the upper layer 12a. The opening 22 and the opening 24 are formed an appropriate distance apart. The void 26 is formed in the lower layer 12b. The void 26 is located below the openings 22 and 24 and has a shape larger than the openings 22 and 24 in a planar view. The mask layer 12 is formed, for example, from a resist. The lower layer 12b uses a resist that is more sensitive to exposure (e.g., EB (Electron Beam) exposure) and development for forming the openings 22 and 24 and the void 26 than the upper layer 12a. As a result, when the openings 22, 24 are formed in the upper layer 12a, a void 26 larger than the openings 22, 24 is formed in the lower layer 12b. The portion of the upper layer 12a located between the openings 22 and 24 is formed so as to float above the void 26.

[0014] As shown in FIG. 1(b), using the mask layer 12 as a mask, the superconducting film 14 is formed on the substrate 10 from diagonally above in the -X direction, as indicated by arrow 40. For example, the superconducting film 14 is formed by oblique vacuum deposition. Since the superconducting film 14 is formed on the substrate 10 from diagonally above in the -X direction, the superconducting film 14 formed in the gap 26 is shifted in the +X direction with respect to the openings 22 and 24. The width of the superconducting film 14 is, for example, about 100 nm to 300 nm, and the thickness is about 10 nm to 100 nm.

[0015] 1(c), while maintaining the vacuum state in which the superconducting film 14 was formed, oxygen is introduced into the chamber to oxidize the surface of the superconducting film 14, thereby forming an insulating film 16 on the surface of the superconducting film 14. The thickness of the insulating film 16 is, for example, about 1 nm to 5 nm.

[0016] As shown in FIG. 2(a), using the mask layer 12 as a mask, the superconducting film 18 is formed on the substrate 10 from diagonally above in the +X direction, as indicated by the arrow 42. For example, the superconducting film 18 is formed by oblique vacuum deposition. Since the superconducting film 18 is formed on the substrate 10 from diagonally above in the +X direction, the superconducting film 18 formed in the gap 26 is shifted in the -X direction relative to the openings 22 and 24. This forms a region 28 where the superconducting film 14 extending in the X-axis direction and the superconducting film 18 extending in the Y-axis direction overlap with the insulating film 16 interposed therebetween. The width of the superconducting film 18 is, for example, approximately 100 nm to 300 nm, and the thickness is approximately 10 nm to 100 nm.

[0017] 2(b), the mask layer 12, the superconducting film 14, the insulating film 16, and the superconducting film 18 formed on the mask layer 12 are removed by a lift-off method. A region 28 where the superconducting film 14 extending in the X-axis direction and the superconducting film 18 extending in the Y-axis direction overlap with the insulating film 16 interposed therebetween becomes a Josephson junction 30.

[0018] Using Figures 3(a) to 5(c), we will explain the issues that arise in Dolan Bridge Josephson devices. Figures 3(a) and 3(b) show the formation of superconducting films 14, 18 on a wafer-like substrate 10 in a Dolan Bridge Josephson device by oblique vacuum deposition. As shown in Figure 3(a), the deposition material from a deposition source 34 located in the -X direction relative to the substrate 10 is vaporized or sublimated, causing the deposition material to be incident on the substrate 10 from diagonally above in the -X direction, forming the superconducting film 14. At this time, the deposition source 34 is not located at infinity relative to the substrate 10 but is placed at a realistic distance, for example, about 50 cm from the substrate 10. Therefore, the incidence angle of the deposition material from the deposition source 34 varies in the Y-axis direction of the substrate 10, as indicated by arrows 40a, 40b, and 40c. That is, the incidence angle of the deposition material from the deposition source 34 differs among region A located on the +Y direction side of the substrate 10, region B located in the center in the Y-axis direction, and region C located on the −Y direction side. Similarly, as shown in FIG. 3( b), the deposition material from the deposition source 34 located in the +X direction relative to the substrate 10 is vaporized or sublimated, so that the deposition material is incident on the substrate 10 from diagonally above in the +X direction, thereby forming the superconducting film 18. Therefore, as indicated by arrows 42a, 42b, and 42c, the incidence angle of the deposition material from the deposition source 34 differs in the Y-axis direction of the substrate 10. That is, the incidence angle differs among region A located on the +Y direction side of the substrate 10, region B located in the center in the Y-axis direction, and region C located on the −Y direction side. The larger the substrate 10, the greater the difference in the incidence angle of the deposition material between region B and regions A and C.

[0019] 4(a) to 4(c) show the incidence angles of the deposition material onto the mask pattern 20 in regions A, B, and C of FIGS. 3(a) and 3(b). As shown in FIGS. 4(a) to 4(c), the openings 22 included in the mask pattern 20 in all of regions A, B, and C extend in the X-axis direction, and the openings 24 extend in the Y-axis direction. In this case, as shown in FIG. 4(b), for region B located in the center in the Y-axis direction, the deposition material enters the openings 22 and 24 from a direction approximately parallel to the X-axis direction, as indicated by arrows 40b and 42b. On the other hand, as shown in FIG. 4(a), for region A located on the +Y-axis side, the deposition material enters the openings 22 and 24 from a direction tilted in the -Y direction with respect to the X-axis direction, as indicated by arrows 40a and 42a. As shown in FIG. 4(c), for region C located on the -Y-axis side, the deposition material enters the openings 22 and 24 from a direction tilted in the +Y direction with respect to the X-axis direction, as indicated by arrows 40c and 42c.

[0020] 5(a) to 5(c) show Josephson junction elements formed in regions A, B, and C in FIGS. 3(a) and 3(b). Note that FIGS. 5(a) to 5(c) illustrate the superconducting film 14 as seen through the insulating film 16. As shown in FIG. 4(b), in region B, the deposition material enters the opening 22 extending in the X-axis direction from a direction substantially parallel to the X-axis direction. Therefore, as shown in FIG. 5(b), the superconducting films 14 and 18 extending in the X-axis direction are formed with a width substantially equal to that of the opening 22. On the other hand, as shown in FIGS. 4(a) and 4(c), in regions A and C, the deposition material enters the opening 22 extending in the X-axis direction from a direction tilted in the -Y direction or +Y direction with respect to the X-axis direction. Therefore, as shown in FIGS. 5(a) and 5(c), the superconducting films 14 and 18 extending in the X-axis direction are formed with a width narrower than that of the opening 22.

[0021] The characteristics of a Josephson junction element are affected by the area of the Josephson junction 30 where the superconducting film 14 and the superconducting film 18 overlap with the insulating film 16 interposed therebetween. For example, in a quantum bit using a transmon in which a Josephson junction element and a capacitor are connected in parallel, if there is variation in the area of the Josephson junction 30, this variation will be reflected in the quantum bit variation and cause a decrease in fidelity. Therefore, as shown in Figures 5(a) to 5(c), if there is variation in the area of the Josephson junction 30 in the Y-axis direction within the substrate 10, the characteristics of the Josephson junction element will vary, resulting in a decrease in the fidelity of the quantum bit. In the future, as the integration of quantum bits progresses and the area of quantum bit chips increases, several quantum bit chips (e.g., 1 to 5) will be formed on a wafer-like substrate 10. In this case, variation in the characteristics of the Josephson junction elements within the quantum bit chip will occur, causing a decrease in the fidelity of the quantum bit.

[0022] Therefore, a manufacturing method for minimizing the variation in the area of the Josephson junctions 30 in the substrate 10 in a Dolan Bridge type Josephson device will be described below.

[0023] FIGS. 6(a) to 10(c) are plan views showing a manufacturing method of a Josephson junction device according to Example 1. FIGS. 6(a), 7(a), 8(a), 9(a), and 10(a) are plan views of a portion corresponding to region A in FIGS. 3(a) and 3(b). FIGS. 6(b), 7(b), 8(b), 9(b), and 10(b) are plan views of a portion corresponding to region B in FIGS. 3(a) and 3(b). FIGS. 6(c), 7(c), 8(c), 9(c), and 10(c) are plan views of a portion corresponding to region C in FIGS. 3(a) and 3(b). In FIGS. 7(a) to 10(c), for clarity, the superconducting film 14, insulating film 16, and superconducting film 18 formed in the voids 26a to 26c are hatched. In addition, in FIGS. 9(a) to 9(c), the openings 22a to 22c and the openings 24a to 24c are shown by dotted lines for clarity of the drawings.

[0024] As shown in FIGS. 6(a) to 6(c), a mask layer 12 having an upper layer 12a and a lower layer 12b is formed on a wafer-like substrate 10 (see also FIGS. 1(a), 3(a), and 3(b)). The substrate 10 is, for example, a high-resistivity silicon substrate, and the mask layer 12 is, for example, formed of resist. Mask patterns 20a, 20b, and 20c are formed in regions A, B, and C of the mask layer 12. As shown in FIG. 6(a), the mask pattern 20a formed in region A includes a horizontally elongated opening 22a extending obliquely from the −X direction toward the +X direction toward the +Y direction, a vertically elongated opening 24a extending in the Y-axis direction, and a void 26a. The opening 24a is provided an appropriate distance away from the opening 22a in the +X direction. The openings 22a and 24a are formed in the upper layer 12a. The void 26a is formed in the lower layer 12b, positioned below the openings 22a and 24a, and has a shape larger than the openings 22a and 24a in a plan view.

[0025] As shown in FIG. 6(b), the mask pattern 20b formed in region B includes a horizontally elongated opening 22b extending in the X-axis direction, a vertically elongated opening 24b extending in the Y-axis direction, and a void 26b. The opening 24b is located an appropriate distance away from the opening 22b in the +X direction. The openings 22b and 24b are formed in the upper layer 12a. The void 26b is larger than the openings 22b and 24b in plan view and is located below the openings 22b and 24b in the lower layer 12b. As shown in FIG. 6(c), the mask pattern 20c formed in region C includes a horizontally elongated opening 22c extending from the −X direction toward the +X direction at an angle toward the −Y direction, a vertically elongated opening 24c extending in the Y-axis direction, and a void 26c. The opening 24c is located an appropriate distance away from the opening 22c in the +X direction. Openings 22c and 24c are formed in upper layer 12a. Void 26c is larger than openings 22c and 24c and is formed in lower layer 12b below openings 22c and 24c.

[0026] In openings 22a, 22b, and 22c, the width of the portion located on the -X direction side is larger than the width of the portion located on the +X direction side. For example, in openings 22a, 22b, and 22c, the length of the wide portion is 80% to 120% of the length of the narrow portion, and may be 85% to 115%, or 90% to 110%.

[0027] The openings 22a, 22b, and 22c have the same width at both the wide and narrow portions. The openings 22a, 22b, and 22c also have the same length. Similarly, the openings 24a, 24b, and 24c also have the same width and length.

[0028] As shown in FIGS. 7(a) to 7(c), a superconducting film 14 is formed on the substrate 10 from diagonally above in the −X direction using the mask layer 12 as a mask by oblique vacuum deposition. For example, an aluminum (Al) film is formed as the superconducting film 14. In region A, as indicated by arrow 40a, the deposition material enters the openings 22a and 24a from a direction tilted in the −Y direction with respect to the X-axis direction. The openings 22a are tilted in the +Y direction from the −X direction toward the +X direction and are formed along the direction of incidence of the deposition material. Therefore, a superconducting film 14 having approximately the same width as the openings 22a is formed in the gap 26a. The superconducting film 14 formed in the gap 26a by the openings 22a and 24a is shifted toward the +X direction with respect to the openings 22a and 24a.

[0029] In region B, as indicated by arrow 40b, the deposition material enters the openings 22b and 24b substantially parallel to the X-axis direction. The openings 22b extend in the X-axis direction and are formed along the direction in which the deposition material is incident. Therefore, even in region B, a superconducting film 14 having substantially the same width as the openings 22b is formed in the gap 26b. The superconducting film 14 formed in the gap 26b by the openings 22b and 24b is shifted toward the +X direction with respect to the openings 22b and 24b.

[0030] In region C, as indicated by arrow 40c, the deposition material enters the openings 22c and 24c from a direction tilted in the +Y direction with respect to the X-axis direction. The openings 22c are tilted in the -Y direction from the -X direction toward the +X direction and are formed along the direction of incidence of the deposition material. Therefore, even in region C, a superconducting film 14 having approximately the same width as the openings 22c is formed in the gap 26c. The superconducting film 14 formed in the gap 26c by the openings 22c and 24c is shifted toward the +X direction with respect to the openings 22c and 24c.

[0031] As shown in Figures 8(a) to 8(c), while maintaining the vacuum state when the superconducting film 14 was formed, oxygen is introduced into the chamber to oxidize the surface of the superconducting film 14, thereby forming an insulating film 16 on the surface of the superconducting film 14.

[0032] As shown in FIGS. 9(a) to 9(c), a superconducting film 18 is formed on the substrate 10 from diagonally above in the +X direction using the mask layer 12 as a mask by oblique vacuum deposition. For example, an aluminum (Al) film is formed as the superconducting film 18. In region A, as indicated by arrow 42a, the deposition material enters the openings 22a and 24a from a direction tilted in the -Y direction with respect to the X-axis direction. Because the opening 22a is tilted in the +Y direction from the -X direction toward the +X direction, the superconducting film 18 formed in the gap 26a by the opening 22a is formed obliquely offset in the -X direction with respect to the superconducting film 14. At this time, because the opening 22a is wider on the -X direction side, a portion of the superconducting film 18 is formed overlapping a portion of the superconducting film 14. The superconducting film 18 formed in the gap 26a by the opening 24a is also formed offset in the -X direction with respect to the opening 24a.

[0033] In region B, as indicated by arrow 42b, the deposition material enters openings 22b and 24b substantially parallel to the X-axis direction. Because opening 22b extends in the X-axis direction, superconducting film 18 formed in gap 26b by opening 22b is shifted in the −X direction with respect to superconducting film 14. A portion of superconducting film 18 is formed overlapping a portion of superconducting film 14. Superconducting film 18 formed in gap 26b by opening 24b is also shifted in the −X direction with respect to opening 24b.

[0034] In region C, as indicated by arrow 42c, the deposition material enters openings 22c and 24c from a direction tilted in the +Y direction with respect to the X-axis direction. Because opening 22c is tilted in the -Y direction from the -X direction toward the +X direction, the superconducting film 18 formed in gap 26c by opening 22c is formed so as to be obliquely shifted in the -X direction with respect to the superconducting film 14. At this time, because opening 22c is wider on the -X direction side, part of superconducting film 18 is formed so as to overlap part of the superconducting film 14. The superconducting film 18 formed in gap 26c by opening 24c is also formed so as to be shifted in the -X direction with respect to the opening 24c.

[0035] In each of the regions A, B, and C, regions 28a, 28b, and 28c are formed where the superconducting film 14 extending in the X-axis direction and the superconducting film 18 extending in the Y-axis direction overlap with the insulating film 16 interposed therebetween.

[0036] 10(a) to 10(c), the mask layer 12, the superconducting film 14 formed on the mask layer 12, the insulating film 16, and the superconducting film 18 are removed by lift-off. Regions 28a, 28b, and 28c where the superconducting film 14 extending in the X-axis direction and the superconducting film 18 extending in the Y-axis direction overlap with the insulating film 16 interposed therebetween become Josephson junctions 30a, 30b, and 30c. As a result, Dolan Bridge-type Josephson junction devices 100 are formed in the regions A, B, and C, respectively.

[0037] As described above, according to the first embodiment, the mask pattern 20b (first mask pattern) located in the region B (first region) of the substrate 10 includes the opening 22b (first opening) and the opening 24b (second opening) as shown in FIG. 6(b). The opening 22b extends along the incident direction of the film forming material when the superconducting film 14 is formed from diagonally above in the −X direction (first diagonal direction) as shown in FIG. 7(b). The opening 24b extends in a direction intersecting with the opening 22b. The mask pattern 20a (second mask pattern) located in the region A (second region) located closer to the edge of the substrate 10 than the region B includes the opening 22a (third opening) and the opening 24a (fourth opening) as shown in FIG. 6(a). As shown in FIG. 7( a), the opening 22a extends obliquely relative to the opening 22b (first opening) along the incident direction of the film-forming material when the superconducting film 14 is formed from diagonally above in the −X direction (first oblique direction). The opening 24a extends in a direction intersecting the opening 22a. As a result, the width of the superconducting film 14 formed by the openings 22a and 22b is approximately the same as the width of the openings 22a and 22b, thereby suppressing variations in the width of the superconducting film 14 formed in regions A and B. This suppresses variations in the area of the Josephson junctions 30a and 30b. The width of the superconducting film 14 formed by the openings 22a and 22b is substantially determined by the width of the openings 22a and 22b, and the widths of the openings 22a and 22b can be precisely controlled, thereby enabling precise control of the width of the superconducting film 14.

[0038] Furthermore, according to the first embodiment, the width of the opening 22b of the mask pattern 20b formed in the region B is the same as the width of the opening 22a of the mask pattern 20a formed in the region A. As a result, the width of the superconducting film 14 formed by the opening 22a is almost the same as the width of the superconducting film 14 formed by the opening 22b. This makes it possible to suppress variations in the areas of the Josephson junctions 30a, 30b. Having the same width also includes cases where the widths differ by the amount of manufacturing error.

[0039] According to the first embodiment, the openings 22a and 24a of the mask pattern 20a are formed in the upper layer 12a of the mask layer 12, and the void 26a is formed in the lower layer 12b below the openings 22a and 24a, with a shape larger than the openings 22a and 24a in plan view. Similarly, the openings 22b and 24b of the mask pattern 20b are formed in the upper layer 12a of the mask layer 12, and the void 26b is formed in the lower layer 12b below the openings 22b and 24b, with a shape larger than the openings 22b and 24b in plan view. By using such mask patterns 20a and 20b, a Josephson junction device 100 as shown in FIGS. 10(a) and 10(b) is formed.

[0040] Furthermore, according to Example 1, the superconducting film 14 is formed obliquely from above in the −X direction (first oblique direction), and the superconducting film 18 is formed obliquely from above in the +X direction (second oblique direction) on the opposite side of the substrate 10 from the formation of the superconducting film 14 (e.g., 180° different). The mask patterns 20a and 20b are arranged side by side in the Y-axis direction (first direction) that intersects (e.g., is perpendicular to) the −X and +X directions, as shown in FIGS. 6(a) and 6(b). The opening 24b of the mask pattern 20b is spaced apart from the opening 22b in the X-axis direction (second direction perpendicular to the first direction). The opening 24a of the mask pattern 20a is spaced apart from the opening 22a in the X-axis direction and extends in the same direction as the opening 24b. This reduces variations in the width of the superconducting film 18 formed in regions A and B. This reduces variations in the areas of the Josephson junctions 30a and 30b.

[0041] Furthermore, according to the first embodiment, the mask pattern 20c (third mask pattern) located in the region C (third region) opposite the region B from the region A of the substrate 10 includes an opening 22c (fifth opening) and an opening 24c (sixth opening) as shown in FIG. 6(c). As shown in FIG. 7(c), the opening 22c extends obliquely opposite the opening 22a with respect to the opening 22b (first opening) along the incident direction of the film-forming material when the superconducting film 14 is formed from diagonally above in the -X direction (first oblique direction). The opening 24c is spaced apart from the opening 22c in the X-axis direction and extends in the same direction as the openings 24a and 24b. As a result, the width of the superconducting film 14 formed by the opening 22c is approximately the same as the width of the opening 22c. This makes it possible to suppress variations in the width of the superconducting film 14 formed in the regions A, B, and C. Furthermore, it is also possible to suppress variations in the width of the superconducting film 18 formed in the regions A, B, and C. Therefore, variations in the areas of the Josephson junctions 30a, 30b, and 30c can be suppressed.

[0042] In Example 1, the superconducting film 14 is formed by deposition from diagonally above in the -X direction, and the superconducting film 18 is formed by deposition from diagonally above in the +X direction. Here, the angle of the diagonally above direction is generally 45° from the normal direction of the substrate, but deposition from diagonally above at a different angle of 60° from 0° (normal direction) on one side may also be performed.

[0043] In the first embodiment, the openings 22a to 22c of the mask patterns 20a to 20c extend along the incident direction of the film-forming material in the film-forming (first film-forming) step of the superconducting film 14. However, the present invention is not limited to this case, and the openings 22a to 22c may extend along the incident direction of the film-forming material in the film-forming (second film-forming) step of the superconducting film 18. [Example]

[0044] In Example 2, a Manhattan-type Josephson device will be described. FIGS. 11(a) to 12(b) are diagrams showing a method for manufacturing a Manhattan-type Josephson device. The upper figures in FIGS. 11(a) to 12(b) are plan views showing the method for manufacturing a Manhattan-type Josephson device. The middle figures are AA cross-sectional views of the upper figures, and the lower figures are BB cross-sectional views of the upper figures. In the upper plan views in FIGS. 11(b) to 12(b), the superconducting film 14, insulating film 16, and superconducting film 18 formed in the void 26 are hatched for clarity.

[0045] As shown in FIG. 11(a), a mask layer 12 is formed on a substrate 10. The mask layer 12 has an upper layer 12a and a lower layer 12b, as in Example 1. A mask pattern 50 including an opening 52, an opening 54, and a void 56 is formed in the mask layer 12. The opening 52 extends in the X-axis direction, and the opening 54 extends in the Y-axis direction, intersecting the opening 52, and both are formed in the upper layer 12a. The void 56 is formed in the lower layer 12b. The void 56 is located below the openings 52, 54, and is larger than the openings 52, 54 in a plan view.

[0046] As shown in FIG. 11( b), using the mask layer 12 as a mask, the superconducting film 14 is formed on the substrate 10 from diagonally above in the −X direction, as indicated by the arrow 70. The superconducting film 14 is formed, for example, by oblique vacuum deposition. Since the superconducting film 14 is formed on the substrate 10 from diagonally above in the −X direction, by setting the width of the opening 54 to an appropriate size, the superconducting film 14 extending in the Y-axis direction is not formed in the void 26, and only the superconducting film 14 extending in the X-axis direction is formed. For example, by making the width of the opening 54 smaller than the thickness of the upper layer 12a, the superconducting film 14 extending in the Y-axis direction can be prevented from being formed in the void 26. The superconducting film 14 is formed offset in the +X direction relative to the opening 52.

[0047] As shown in FIG. 11(c), while maintaining the vacuum state when the superconducting film 14 was formed, oxygen is introduced into the chamber to oxidize the surface of the superconducting film 14, thereby forming an insulating film 16 on the surface of the superconducting film 14.

[0048] As shown in FIG. 12( a), using the mask layer 12 as a mask, the superconducting film 18 is formed on the substrate 10 from diagonally above in the +Y direction, as indicated by the arrow 72. The superconducting film 18 is formed, for example, by oblique vacuum deposition. Since the superconducting film 18 is formed on the substrate 10 from diagonally above in the +Y direction, by setting the width of the opening 52 to an appropriate size, the superconducting film 18 extending in the X-axis direction is not formed in the void 26, and only the superconducting film 18 extending in the Y-axis direction is formed. For example, by making the width of the opening 52 smaller than the thickness of the upper layer 12a, the superconducting film 18 extending in the X-axis direction can be prevented from being formed in the void 26. The superconducting film 18 is formed offset in the −Y direction with respect to the opening 54. This forms a region 58 where the superconducting film 14 extending in the X-axis direction and the superconducting film 18 extending in the Y-axis direction overlap with each other via the insulating film 16.

[0049] 12(b), the mask layer 12, the superconducting film 14, the insulating film 16, and the superconducting film 18 formed on the mask layer 12 are removed by lift-off. A region 58 where the superconducting film 14 extending in the X-axis direction and the superconducting film 18 extending in the Y-axis direction overlap with the insulating film 16 interposed therebetween becomes a Josephson junction 60.

[0050] Using Figures 13(a) to 15(i), we will explain the issues that arise in Manhattan-type Josephson junction devices. Figures 13(a) and 13(b) show the formation of superconducting films 14, 18 on a wafer-shaped substrate 10 in a Manhattan-type Josephson junction device by oblique vacuum deposition. As shown in Figure 13(a), the deposition material from a deposition source 34 located in the -X direction relative to the substrate 10 is vaporized or sublimated, causing the deposition material to be incident on the substrate 10 from obliquely above in the -X direction, thereby forming the superconducting film 14. At this time, the deposition source 34 is not located at infinity relative to the substrate 10 but is located at a realistic distance, for example, approximately 50 cm from the substrate 10. As a result, the incidence angle of the deposition material from the deposition source 34 varies in the Y-axis direction of the substrate 10, as indicated by arrows 70a, 70b, and 70c. That is, the incidence angle of the deposition material from the deposition source 34 differs among regions A, B, and C located on the +Y direction side of the substrate 10, regions D, E, and F located in the center in the Y-axis direction, and regions G, H, and I located on the −Y direction side. Similarly, as shown in FIG. 13( b), the deposition material from the deposition source 34 located in the +Y direction with respect to the substrate 10 is vaporized or sublimated, so that the deposition material is incident on the substrate 10 from diagonally above in the +Y direction, thereby forming the superconducting film 18. Therefore, as indicated by arrows 72a, 72b, and 72c, the incidence angle of the deposition material from the deposition source 34 differs in the X-axis direction of the substrate 10. That is, the incidence angle of the deposition material from the deposition source 34 differs among regions A, D, and G located on the −X direction side of the substrate 10, regions B, E, and H located in the center in the X-axis direction, and regions C, F, and I located on the +X direction side.

[0051] 14(a) to 14(i) show the incidence angles of the deposition material onto the mask pattern 50 in regions A to I of FIGS. 13(a) and 13(b). As shown in FIGS. 14(a) to 14(i), the openings 52 included in the mask pattern 50 in all of regions A to I extend in the X-axis direction, and the openings 54 extend in the Y-axis direction. In this case, as shown in FIGS. 14(d) to 14(f), for regions D, E, and F located at the center of the substrate 10 in the Y-axis direction, the deposition material enters the openings 52 from a direction approximately parallel to the X-axis direction, as indicated by arrow 70b. On the other hand, as shown in FIGS. 14(a) to 14(c), for regions A, B, and C located on the +Y-direction side of the substrate 10, the deposition material enters the openings 52 from a direction tilted in the −Y direction with respect to the X-axis direction, as indicated by arrow 70a. As shown in Figures 14(g) to 14(i), for regions G, H, and I located on the -Y direction side of the substrate 10, the deposition material enters the opening 52 from a direction tilted in the +Y direction with respect to the X-axis direction, as indicated by arrow 70c.

[0052] 14(b), 14(e), and 14(h), for regions B, E, and H located at the center in the X-axis direction of the substrate 10, the deposition material enters the opening 54 from a direction approximately parallel to the Y-axis direction, as indicated by arrow 72b. On the other hand, for regions A, D, and G located on the −X-direction side of the substrate 10, as indicated by arrow 72a, the deposition material enters the opening 54 from a direction tilted toward the +X direction with respect to the Y-axis direction, as indicated by arrow 72a. For regions C, F, and I located on the +X-direction side of the substrate 10, as indicated by arrow 72c, the deposition material enters the opening 54 from a direction tilted toward the −X direction with respect to the Y-axis direction, as indicated by arrow 72c.

[0053] 15(a) to 15(i) show Josephson junction elements formed in regions A to I of FIGS. 13(a) and 13(b). In FIGS. 15(a) to 15(i), the superconducting film 14 is shown as seen through the insulating film 16. As shown in FIGS. 14(d) to 14(f), in regions D, E, and F, the deposition material enters the openings 52 extending in the X-axis direction from a direction substantially parallel to the X-axis direction. Therefore, as shown in FIGS. 15(d) to 15(f), the superconducting film 14 extending in the X-axis direction is formed with a width substantially equal to that of the openings 52. On the other hand, as shown in FIGS. 14(a) to 14(c), in regions A, B, and C, the deposition material enters the openings 52 extending in the X-axis direction from a direction tilted in the -Y direction with respect to the X-axis direction. 15(a) to 15(c), the superconducting film 14 formed to extend in the X-axis direction is formed to be narrower than the width of the opening 52. As shown in FIGS. 14(g) to 14(i), in regions G, H, and I, the deposition material enters the opening 52 extending in the X-axis direction from a direction tilted toward the +Y direction with respect to the X-axis direction. Therefore, as shown in FIGS. 15(g) to 15(i), the superconducting film 14 formed to extend in the X-axis direction is formed to be narrower than the width of the opening 52.

[0054] 14(b), 14(e), and 14(h), in regions B, E, and H, the deposition material enters the openings 54 extending in the Y-axis direction from a direction substantially parallel to the Y-axis direction. Therefore, as shown in FIGS. 15(b), 15(e), and 15(h), the superconducting film 18 extending in the Y-axis direction is formed with a width substantially equal to the width of the openings 54. On the other hand, as shown in FIGS. 14(a), 14(d), and 14(g), in regions A, D, and G, the deposition material enters the openings 54 extending in the Y-axis direction from a direction tilted toward the +X direction with respect to the Y-axis direction. Therefore, as shown in FIGS. 15(a), 15(d), and 15(g), the superconducting film 18 extending in the Y-axis direction is formed with a width narrower than the width of the openings 54. 14(c), 14(f), and 14(i), in regions C, F, and I, the deposition material enters the opening 54 extending in the Y-axis direction from a direction tilted toward the −X direction with respect to the Y-axis direction. Therefore, as shown in FIGS. 15(c), 15(f), and 15(i), the superconducting film 14 formed to extend in the Y-axis direction is formed to be narrower than the width of the opening 54.

[0055] The characteristics of the Josephson junction element are affected by the area of the Josephson junction 60 where the superconducting film 14 and the superconducting film 18 overlap with the insulating film 16 interposed therebetween. Variations in the area of the Josephson junction 60 cause variations in the characteristics of the Josephson junction element, which reduces the fidelity of the quantum bit. Therefore, as shown in Figures 15(a) to 15(i), variations in the area of the Josephson junction 60 within the substrate 10 cause variations in the characteristics of the Josephson junction element, which in turn reduces the fidelity of the quantum bit.

[0056] Therefore, a manufacturing method that can minimize variations in the area of the Josephson junctions 60 in the substrate 10 in a Manhattan-type Josephson device will be described below.

[0057] 16(a) to 20(i) are plan views showing a manufacturing method of a Josephson junction device according to Example 2. In FIGS. 16 to 20, (a) is a plan view of a portion corresponding to region A in FIGS. 13(a) and 13(b), (b) is a plan view of a portion corresponding to region B, (c) is a plan view of a portion corresponding to region C, and (d) is a plan view of a portion corresponding to region D. (e) is a plan view of a portion corresponding to region E, (f) is a plan view of a portion corresponding to region F, (g) is a plan view of a portion corresponding to region G, (h) is a plan view of a portion corresponding to region H, and (i) is a plan view of a portion corresponding to region I. In FIGS. 17(a) to 20(c), for clarity, the superconducting film 14, insulating film 16, and superconducting film 18 formed in the voids 56a to 56i are shown hatched.

[0058] As shown in FIGS. 16(a) to 16(i), a mask layer 12 having an upper layer 12a and a lower layer 12b is formed on a wafer-like substrate 10 (see also FIGS. 11(a), 13(a), and 13(b)). Mask patterns 50a to 50i are formed in regions A to I of the mask layer 12. As shown in FIGS. 16(a) to 16(c), the mask patterns 50a, 50b, and 50c formed in regions A, B, and C include openings 52a, 52b, and 52c that extend from the −X direction toward the +X direction at an inclination toward the +Y direction. Furthermore, as shown in FIG. 16(a), the mask pattern 50a includes, in addition to the opening 52a, an opening 54a that extends from the −Y direction toward the +Y direction at an inclination toward the +X direction, and a void 56a. The void 56a is larger than the openings 52a and 54a in a plan view and is formed below the openings 52a and 54a. As shown in FIG. 16(b), mask pattern 50b includes, in addition to opening 52b, opening 54b extending in the Y-axis direction and void 56b. Void 56b is larger than openings 52b and 54b in plan view and is formed below openings 52b and 54c. As shown in FIG. 16(c), mask pattern 50c includes, in addition to opening 52c, opening 54c extending obliquely in the −X direction from the −Y direction toward the +Y direction, and void 56c. Void 56c is larger than openings 52c and 54c in plan view and is formed below openings 52c and 54c.

[0059] As shown in FIGS. 16(d) to 16(f), mask patterns 50d, 50e, and 50f formed in regions D, E, and F include openings 52d, 52e, and 52f extending in the X-axis direction. As shown in FIG. 16(d), mask pattern 50d includes, in addition to opening 52d, opening 54d that extends obliquely toward the +X direction from the -Y direction toward the +Y direction, and void 56d. In plan view, void 56d is larger than openings 52d and 54d and is formed below openings 52d and 54d. As shown in FIG. 16(e), mask pattern 50e includes, in addition to opening 52e, opening 54e that extends in the Y-axis direction and void 56e. In plan view, void 56e is larger than openings 52e and 54e and is formed below openings 52e and 54e. 16(f), mask pattern 50f includes, in addition to opening 52f, opening 54f that extends obliquely in the -X direction from the -Y direction toward the +Y direction, and void 56f. Void 56f is larger than openings 52f and 54f in plan view and is formed below openings 52f and 54f.

[0060] As shown in FIGS. 16(g) to 16(i), mask patterns 50g, 50h, and 50i formed in regions G, H, and I include openings 52g, 52h, and 52i extending from the −X direction toward the +X direction at an inclination toward the −Y direction. As shown in FIG. 16(g), mask pattern 50g also includes, in addition to opening 52g, opening 54g extending from the −Y direction toward the +Y direction at an inclination toward the +X direction, and void 56g. In plan view, void 56g is larger than openings 52g and 54g and is formed below openings 52g and 54g. As shown in FIG. 16(h), mask pattern 50h also includes, in addition to opening 52h, opening 54h extending in the Y-axis direction and void 56h. In plan view, void 56h is larger than openings 52h and 54h and is formed below openings 52h and 54h. 16(i), the mask pattern 50i includes, in addition to the opening 52i, an opening 54i that extends from the -Y direction toward the +Y direction at an angle toward the -X direction, and a void 56i. The void 56i is larger than the openings 52i and 54i in plan view and is formed below the openings 52i and 54i.

[0061] The openings 52a-52i have the same width and length. Similarly, the openings 54a-54i have the same width and length. The openings 52a-52i and the openings 54a-54i have, for example, the same width and length, but at least one of the width and length may be different.

[0062] As shown in FIGS. 17(a) to 17(i), a superconducting film 14 is formed on the substrate 10 from diagonally above in the −X direction using the mask layer 12 as a mask by oblique vacuum deposition. For example, an aluminum (Al) film is formed as the superconducting film 14. As shown in FIGS. 17(a) to 17(c), in regions A, B, and C, the deposition material enters the openings 52a, 52b, and 52c from a direction tilted in the −Y direction with respect to the X-axis direction, as indicated by arrow 70a. The openings 52a, 52b, and 52c are tilted in the +Y direction from the −X direction toward the +X direction and are formed along the direction of incidence of the deposition material. Therefore, a superconducting film 14 having approximately the same width as the openings 52a, 52b, and 52c is formed in the voids 56a, 56b, and 56c. The superconducting film 14 formed in the gaps 56a, 56b, and 56c by the openings 52a, 52b, and 52c is shifted toward the +X direction with respect to the openings 52a, 52b, and 52c. Furthermore, by setting the width dimensions of the openings 54a, 54b, and 54c to appropriate sizes, the superconducting film 14 extending in the Y-axis direction is not formed in the gaps 56a, 56b, and 56c. For example, the width dimensions of the openings 54a, 54b, and 54c are set smaller than the thickness dimension of the upper layer 12a of the mask layer 12.

[0063] As shown in Figures 17(d) to 17(f), in regions D, E, and F, the vapor deposition material enters the openings 52d, 52e, and 52f approximately parallel to the X-axis direction, as indicated by arrows 70b. The openings 52d, 52e, and 52f extend in the X-axis direction and are formed along the direction in which the vapor deposition material enters. Therefore, a superconducting film 14 having approximately the same width as the openings 52d, 52e, and 52f is formed in the gaps 56d, 56e, and 56f. The superconducting film 14 formed in the gaps 56d, 56e, and 56f by the openings 52d, 52e, and 52f is shifted toward the +X direction relative to the openings 52d, 52e, and 52f. Furthermore, by setting the widths of the openings 54d, 54e, and 54f to an appropriate size, a superconducting film 14 extending in the Y-axis direction is not formed in the gaps 56d, 56e, and 56f. For example, the width of the openings 54d, 54e, and 54f is set smaller than the thickness of the upper layer 12a of the mask layer 12.

[0064] As shown in Figures 17(g) to 17(i), in regions G, H, and I, the deposition material enters the openings 52g, 52h, and 52i from a direction tilted toward the +Y direction with respect to the X-axis direction, as indicated by arrow 70c. The openings 52g, 52h, and 52i are tilted toward the -Y direction from the -X direction toward the +X direction and are formed along the direction of incidence of the deposition material. Therefore, a superconducting film 14 having approximately the same width as the openings 52g, 52h, and 52i is formed in the gaps 56g, 56h, and 56i. The superconducting film 14 formed in the gaps 56g, 56h, and 56i by the openings 52g, 52h, and 52i is shifted toward the +X direction with respect to the openings 52g, 52h, and 52i. Furthermore, by setting the width of the openings 54g, 54h, and 54i to an appropriate size, the superconducting film 14 extending in the Y-axis direction is not formed in the gaps 56g, 56h, and 56i. For example, the width of the openings 54g, 54h, and 54i is set smaller than the thickness of the upper layer 12a of the mask layer 12.

[0065] As shown in Figures 18(a) to 18(i), while maintaining the vacuum state when the superconducting film 14 was formed, oxygen is introduced into the chamber to oxidize the surface of the superconducting film 14, thereby forming an insulating film 16 on the surface of the superconducting film 14.

[0066] As shown in Figures 19(a) to 19(i), a superconducting film 18 is formed on the substrate 10 from diagonally above in the +Y direction using the mask layer 12 as a mask by oblique vacuum deposition. For example, an aluminum (Al) film is formed as the superconducting film 18. As shown in Figures 19(a), 19(d), and 19(g), in regions A, D, and G, the deposition material enters the openings 54a, 54d, and 54g from a direction tilted in the +X direction with respect to the Y-axis direction, as indicated by arrow 72a. The openings 54a, 54d, and 54g are tilted in the -X direction from the +Y direction toward the -Y direction and are formed along the direction of incidence of the deposition material. Therefore, a superconducting film 18 having approximately the same width as the openings 54a, 54d, and 54g is formed in the gaps 56a, 56d, and 56g. The superconducting film 18 formed in the gaps 56a, 56d, and 56g by the openings 54a, 54d, and 54g is shifted toward the -Y direction with respect to the openings 54a, 54d, and 54g. Also, by setting the width dimensions of the openings 52a, 52d, and 52g to an appropriate size, the superconducting film 18 extending in the X-axis direction is not formed in the gaps 56a, 56d, and 56g. For example, the width dimensions of the openings 52a, 52d, and 52g are set smaller than the thickness dimension of the upper layer 12a of the mask layer 12.

[0067] As shown in Figures 19(b), 19(e), and 19(h), in regions B, E, and H, the vapor deposition material enters the openings 54b, 54e, and 54h in a direction generally parallel to the Y-axis direction, as indicated by arrow 72b. The openings 54b, 54e, and 54h extend in the Y-axis direction and are formed along the direction of incidence of the vapor deposition material. Therefore, a superconducting film 18 having approximately the same width as the openings 54b, 54e, and 54h is formed in the gaps 56b, 56e, and 56h. The superconducting film 18 formed in the gaps 56b, 56e, and 56h by the openings 54b, 54e, and 54h is shifted toward the -Y direction relative to the openings 54b, 54e, and 54h. Furthermore, by setting the widths of the openings 52b, 52e, and 52h to an appropriate size, a superconducting film 18 extending in the X-axis direction is not formed in the gaps 56b, 56e, and 56h. For example, the width of the openings 52b, 52e, and 52h is set smaller than the thickness of the upper layer 12a of the mask layer 12.

[0068] As shown in Figures 19(c), 19(f), and 19(i), in regions C, F, and I, the deposition material enters the openings 54c, 54f, and 54i from a direction tilted in the -X direction with respect to the Y-axis direction, as indicated by arrow 72c. The openings 54c, 54f, and 54i are tilted in the +X direction from the +Y direction toward the -Y direction and are formed along the direction of incidence of the deposition material. Therefore, a superconducting film 18 having approximately the same width as the openings 54c, 54f, and 54i is formed in the gaps 56c, 56f, and 56i. The superconducting film 18 formed in the gaps 56c, 56f, and 56i by the openings 54c, 54c, and 54i is shifted in the -Y direction with respect to the openings 54c, 54f, and 52i. Furthermore, by setting the widths of the openings 52c, 52f, and 52i to appropriate sizes, the superconducting film 18 extending in the X-axis direction is not formed in the voids 56c, 56f, and 56i. For example, the widths of the openings 52c, 52f, and 52i are set smaller than the thickness of the upper layer 12a of the mask layer 12.

[0069] In each of the regions A to I, regions 58a to 58i are formed where the superconducting film 14 extending in the X-axis direction and the superconducting film 18 extending in the Y-axis direction overlap with the insulating film 16 interposed therebetween.

[0070] 20(a) to 20(c), the mask layer 12, and the superconducting film 14, insulating film 16, and superconducting film 18 formed on the mask layer 12 are removed by lift-off. Regions 58a to 58i where the superconducting film 14 extending in the X-axis direction and the superconducting film 18 extending in the Y-axis direction overlap with the insulating film 16 interposed therebetween become Josephson junctions 60a to 60i. As a result, Manhattan-type Josephson junction devices 200 are formed in each of the regions A to I.

[0071] As described above, according to the second embodiment, the mask pattern 50e (first mask pattern) located in the region E (first region) of the substrate 10 includes the opening 52e (first opening) and the opening 54e (second opening) as shown in FIG. 16(e). The opening 52e extends along the incident direction of the film forming material when the superconducting film 14 is formed from diagonally above in the −X direction (first diagonal direction) as shown in FIG. 17(e). The opening 54e extends so as to intersect with the opening 52e. The mask pattern 50b (second mask pattern) located in the region B (second region) located closer to the edge of the substrate 10 than the region E includes the opening 52b (third opening) and the opening 54b (fourth opening) as shown in FIG. 16(b). As shown in FIG. 17(b), the opening 52b extends obliquely relative to the opening 52e (first opening) along the incident direction of the film-forming material when the superconducting film 14 is formed from diagonally above in the −X direction (first oblique direction). The opening 54b extends intersecting with the opening 52b. As a result, the width of the superconducting film 14 formed by the openings 52b and 52e is approximately the same as the width of the openings 52b and 52e, thereby suppressing variations in the width of the superconducting film 14 formed in regions B and E. This suppresses variations in the areas of the Josephson junctions 60b and 60e.

[0072] Furthermore, according to the second embodiment, the width of the opening 52e of the mask pattern 50e formed in the region E is the same as the width of the opening 52b of the mask pattern 50b formed in the region B. As a result, the width of the superconducting film 14 formed by the opening 52b is almost the same as the width of the superconducting film 14 formed by the opening 52e. This makes it possible to suppress variations in the areas of the Josephson junctions 60b, 60e. The phrase "same width" includes cases where the widths differ by the amount of manufacturing error.

[0073] According to the second embodiment, the openings 52b and 54b of the mask pattern 50b are formed in the upper layer 12a of the mask layer 12, and the void 56b is formed in the lower layer 12b below the openings 52b and 54b, with a shape larger than the openings 52b and 54b in plan view. Similarly, the openings 52e and 54e of the mask pattern 50e are formed in the upper layer 12a of the mask layer 12, and the void 56e is formed in the lower layer 12b below the openings 52e and 54e, with a shape larger than the openings 52e and 54e in plan view. By using such mask patterns 50b and 50e, a Josephson junction device 200 as shown in FIGS. 20(b) and 20(e) is formed.

[0074] Furthermore, according to the second embodiment, the superconducting film 14 is formed obliquely from above in the −X direction (first oblique direction), and the superconducting film 18 is formed obliquely from above in the +Y direction (second oblique direction), which is a direction intersecting (e.g., a direction 90° different from) the direction in which the superconducting film 14 is formed with respect to the substrate 10. The mask patterns 50b and 50e are arranged side by side in the Y-axis direction. The openings 52b and 52e of the mask patterns 50b and 50e extend along the direction of incidence of the film-forming material in film-forming from above in the −X direction (first film-forming). The openings 54e of the mask patterns 50e extend along the direction of incidence of the film-forming material in film-forming from above in the +Y direction (second film-forming). The openings 54b of the mask patterns 50b extend in the same direction as the openings 54e of the mask patterns 50e, along the direction of incidence of the film-forming material in film-forming from above in the +Y direction (second film-forming). As a result, the width of the superconducting film 14 formed by the openings 52b and 52e is approximately the same as the width of the openings 52b and 52e. The width of the superconducting film 18 formed by the openings 54b and 54e is approximately the same as the width of the openings 54b and 54e. Therefore, variations in the areas of the Josephson junctions 60b and 60e can be suppressed.

[0075] Furthermore, according to Example 2, a mask pattern 50h (third mask pattern) located in region H (third region) on the opposite side of region E from region B of substrate 10 includes an opening 52h (fifth opening) and an opening 54h (sixth opening) as shown in FIG. 16(h). As shown in FIG. 17(h), opening 52h extends obliquely opposite opening 52b with respect to opening 52e (first opening) along the incident direction of the film formation material for forming superconducting film 14 (first film formation) from diagonally above in the -X direction. As shown in FIG. 19(h), opening 54h intersects opening 52h and extends in the same direction as openings 54b and 54e along the incident direction of the film formation material for forming superconducting film 18 (second film formation) from the +Y direction. As a result, the width of the superconducting film 14 formed by the opening 52h is approximately the same as the width of the opening 52h, and the width of the superconducting film 18 formed by the opening 54h is approximately the same as the width of the opening 54h. Therefore, the variation in the width of the superconducting films 14, 18 formed in region H relative to the width of the superconducting films 14, 18 formed in regions B, E is reduced, and the variation in the areas of the Josephson junctions 60b, 60e, 60h can be reduced.

[0076] Furthermore, according to the second embodiment, a mask pattern 50f (fourth mask pattern) located in a region F (fourth region) that is at a 90° angle to the region B with respect to the center of the substrate 10 includes an opening 52f (seventh opening) and an opening 54f (eighth opening), as shown in FIG. 16(f). As shown in FIG. 17(f), the opening 52f extends in the same direction as the opening 52e (first opening) along the incident direction of the film formation material for the deposition of the superconducting film 14 (first film formation) from diagonally above in the -X direction. As shown in FIG. 19(f), the opening 54f intersects with the opening 52f and extends at an angle relative to the opening 54e (second opening) along the incident direction of the film formation material for the deposition of the superconducting film 18 (second film formation) from diagonally above in the +Y direction. As a result, the width of the superconducting film 14 formed by the opening 52f is approximately the same as the width of the opening 52f, and the width of the superconducting film 18 formed by the opening 54f is approximately the same as the width of the opening 54f. Therefore, the variation in the width of the superconducting films 14, 18 formed in the region F relative to the width of the superconducting films 14, 18 formed in the regions B, E is reduced, and the variation in the areas of the Josephson junctions 60b, 60e, 60f can be reduced.

[0077] Furthermore, according to Example 2, mask pattern 50c (fifth mask pattern) located in region C (fifth region), which is at a 45° angle with region B relative to the center of substrate 10, includes opening 52c (ninth opening) and opening 54c (tenth opening), as shown in FIG. 16(c). As shown in FIG. 17(c), opening 52c extends at an angle relative to opening 52e (first opening) along the direction of incidence of film formation material for film formation (first film formation) of superconducting film 14 from diagonally above in the -X direction. As shown in FIG. 19(c), opening 54c intersects opening 52c and extends at an angle relative to opening 54e (second opening) along the direction of incidence of film formation material for film formation (second film formation) of superconducting film 18 from diagonally above in the +Y direction. As a result, the width of the superconducting film 14 formed by the opening 52c is approximately the same as the width of the opening 52c, and the width of the superconducting film 18 formed by the opening 54c is approximately the same as the width of the opening 54c. Therefore, the variation in the width of the superconducting films 14, 18 formed in the region C relative to the width of the superconducting films 14, 18 formed in the regions B, E is suppressed, and the variation in the areas of the Josephson junctions 60b, 60e, 60c can be suppressed.

[0078] In Example 2, the superconducting film 14 is formed by deposition from diagonally above in the −X direction, and the superconducting film 18 is formed by deposition from diagonally above in the +Y direction. Here, the angle of the diagonally above direction is generally 45° or the like from the normal direction of the substrate, but deposition from diagonally above at an angle of 30° to 60° may also be used in relation to the thickness of the upper layer 12a of the mask layer 12.

[0079] Although the first and second embodiments illustrate the case where the superconducting films 14, 18 are formed by oblique deposition, the superconducting films 14, 18 may be formed by a method other than oblique deposition as long as they are formed by deposition from an oblique direction. The substrate 10 may be a material other than a silicon substrate, such as a sapphire substrate. The superconducting films 14, 18 may be a material other than an aluminum (Al) film, such as a niobium (Nb) film, a niobium nitride (NbN) film, a tantalum (Ta) film, a tantalum nitride (TaN), or a titanium nitride (TiN) film. The insulating film 16 may be a material other than an aluminum oxide.

[0080] Here, the relationship between the intersection angle of the superconducting film 14 and the superconducting film 18 and the area of the Josephson junctions 30, 60 will be explained. Fig. 21 is a plan view of a model used to investigate the correlation between the intersection angle of the superconducting film 14 and the superconducting film 18 and the area of the Josephson junctions 30, 60. As shown in Fig. 21, the case where the superconducting film 14 and the superconducting film 18 are perpendicular to each other is taken as a reference, and the angle at which the superconducting film 14 is tilted from this reference is taken as θ1, and the angle at which the superconducting film 18 is tilted from this reference is taken as θ2. The area of the Josephson junctions 30, 60 is taken as S, and the widths of the superconducting films 14, 18 are both taken as a.

[0081] Table 1 shows the relationship between the sum of angles θ1 and θ2, the area S of the Josephson junctions 30 and 60, the rate of change P of area S when angle θ1 + angle θ2 is used as the base, and the reciprocal of area S, 1 / S. As shown in Table 1, the larger the sum of angles θ1 and θ2, the larger the area S of the Josephson junctions 30 and 60 becomes, and as a result, the reciprocal of area S, 1 / S, becomes smaller. The reciprocal of area S, 1 / S, is proportional to the resistance. When angle θ1 + angle θ2 is 8° or less, the rate of change of the reciprocal of area S, 1 / S, is 1% or less. [Table 1]

[0082] By the manufacturing methods shown in Examples 1 and 2, the angle θ1+θ2 between the superconducting film 14 and the superconducting film 18 in the plurality of Josephson junction devices 100, 200 formed in the substrate 10 can be kept within 8°. For example, when a 3-inch wafer is used as the substrate 10 and the distance between the substrate 10 and the deposition source 34 is approximately 50 cm, the angle θ1+θ2 is kept within 8°. Therefore, the rate of change in the reciprocal 1 / S of the area S of the Josephson junctions 30, 60 of the plurality of Josephson junction devices 100, 200 formed in the substrate 10 can be kept within 1%. When the rate of change in the reciprocal 1 / S is kept within 1%, the change in the characteristics of the Josephson junction devices 100, 200 falls within an allowable range.

[0083] Therefore, in Example 1, the ratio of the area of the Josephson junctions 30a formed by the mask pattern 20a (second mask pattern) to the area of the Josephson junctions 30b formed by the mask pattern 20b (first mask pattern) is 99% or more and 101% or less. This makes it possible to suppress variations in characteristics between the Josephson junction devices 100 having the Josephson junctions 30a and the Josephson junctions 30b. In Example 2, the ratio of the area of the Josephson junctions 60b formed by the mask pattern 50b (second mask pattern) to the area of the Josephson junctions 60e formed by the mask pattern 50e (first mask pattern) is 99% or more and 101% or less. This makes it possible to suppress variations in characteristics between the Josephson junction devices 200 having the Josephson junctions 60b and the Josephson junctions 60e. [Example]

[0084] Fig. 22 is a circuit diagram of a quantum bit 300 according to Example 3. As shown in Fig. 22, the quantum bit 300 includes a transmon 80 including the Josephson device 100 of Example 1 or the Josephson device 200 of Example 2, and a capacitor 82 connected in parallel to the Josephson device 100, 200.

[0085] 23(a) and 23(b) are plan views showing a quantum bit 300 according to a third embodiment. FIG. 23(a) includes a Josephson device 100 according to the first embodiment, and FIG. 23(b) includes a Josephson device 200 according to the second embodiment. As shown in FIG. 23(a), a Josephson device 100 is formed by the manufacturing method of the first embodiment, and a capacitor 82 connected in parallel to the Josephson device 100 is formed. The capacitor 82 is formed between the electrode films 84 and 86 connected to the Josephson device 100, for example, by arranging the electrode films 84 and 86 opposite each other. Similarly, as shown in FIG. 23(b), a Josephson device 200 is formed by the manufacturing method of the second embodiment, and a capacitor 82 connected in parallel to the Josephson device 200 is formed. The capacitor 82 is formed between the electrode films 84 and 86 connected to the Josephson device 200, for example, by arranging the electrode films 84 and 86 opposite each other.

[0086] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0087] 10 Substrate 12 Mask Layer 12a upper layer 12b Lower layer 14 Superconducting film 16. Insulating film 18 Superconducting film 20~20c Mask Pattern 22~22c opening 24~24c opening 26~26c void 28~28c Overlapping area 30~30c Josephson junction 34 Vapor deposition source 40, 42 Arrows 50~50i Mask Pattern 52~52i opening 54~54i opening 56~56i void 58~58i Overlapping Area 60~60i Josephson junction 70, 72 Arrows 80 Transmon 82 Capacitor 84 Electrode membrane 86 Electrode membrane 100, 200 Josephson junction element 300 qubits

Claims

1. forming a mask layer on a substrate; forming a first superconducting film on the substrate by first film deposition from a first oblique direction with respect to the substrate using the mask layer as a mask; forming an insulating film on a surface of the first superconducting film; and forming a second superconducting film having a region overlapping with the first superconducting film via the insulating film by a second film formation from a second oblique direction different from the first oblique direction on the substrate using the mask layer as a mask, the step of forming the mask layer includes: a first mask pattern located in a first region of the substrate, the first mask pattern including a first opening extending along a direction of incidence of a film-forming material in one of the first and second film-forming processes and a second opening extending in a direction intersecting the first opening; and a second mask pattern located in a second region of the substrate, the second mask pattern including a third opening extending obliquely with respect to the first opening along a direction of incidence of a film-forming material in the one of the film-forming processes and a fourth opening extending in a direction intersecting the third opening, the second region being closer to an edge of the substrate than the first region.

2. 2. The method for manufacturing a Josephson junction device according to claim 1, wherein a ratio of an area of a second Josephson junction, which is a region where the first superconducting film and the second superconducting film formed by the second mask pattern overlap with each other via the insulating film, to an area of a first Josephson junction, which is a region where the first superconducting film and the second superconducting film formed by the first mask pattern overlap with each other via the insulating film, is 99% or more and 101% or less.

3. 3. The method for manufacturing a Josephson junction device according to claim 1, wherein the width of the first opening is the same as the width of the third opening.

4. the mask layer has an upper layer and a lower layer, the first mask pattern includes the first opening and the second opening formed in the upper layer, and a first gap located below the first opening and the second opening and formed in the lower layer, the first gap being larger than the first opening and the second opening in a plan view; 3. The method for manufacturing a Josephson junction element according to claim 1, wherein the second mask pattern includes the third opening and the fourth opening formed in the upper layer, and a second void formed in the lower layer below the third opening and the fourth opening, the second void being larger than the third opening and the fourth opening in plan view.

5. 3. The method for manufacturing a Josephson junction element according to claim 1, wherein the step of forming the mask layer includes forming the mask layer having a third mask pattern including a fifth opening located in a third region of the substrate opposite the second region to the first region, the fifth opening extending in a direction in which a film formation material is incident in one of the film formations at an angle opposite to the third opening with respect to the first opening, and a sixth opening extending in a direction intersecting the fifth opening.

6. 3. The method for manufacturing a Josephson junction device according to claim 1, wherein the first film and the second film are formed by oblique deposition.

7. the second film deposition from the second oblique direction is film deposition from an opposite side to the substrate from the first film deposition from the first oblique direction, the first mask pattern and the second mask pattern are arranged side by side in a first direction intersecting the first oblique direction and the second oblique direction, the second opening is spaced apart from the first opening in a second direction perpendicular to the first direction, 3. The method for manufacturing a Josephson junction device according to claim 1, wherein the fourth opening is spaced apart from the third opening in the second direction and extends in the same direction as the second opening.

8. 8. The method for manufacturing a Josephson junction device according to claim 7, wherein the second film deposition from the second oblique direction is a film deposition from a direction that is 180 degrees different with respect to the substrate from the first film deposition from the first oblique direction.

9. the second film deposition from the second oblique direction is film deposition from a direction intersecting the first film deposition from the first oblique direction with respect to the substrate, the first mask pattern and the second mask pattern are provided side by side in the second oblique direction, 3. The method for manufacturing a Josephson junction element according to claim 1, wherein the first opening and the third opening extend along the incident direction of the film-forming material in the first film formation, the second opening intersects with the first opening and extends along the incident direction of the film-forming material in the second film formation, and the fourth opening intersects with the third opening and extends in the same direction as the second opening, along the incident direction of the film-forming material in the second film formation.

10. 10. The method for manufacturing a Josephson junction element according to claim 9, wherein the step of forming the mask layer includes forming the mask layer having a fourth mask pattern including: a seventh opening located in a fourth region that is in a positional relationship of 90° with the second region with respect to the center of the substrate, the seventh opening extending in the same direction as the first opening along the incident direction of the film formation material in the first film formation; and an eighth opening intersecting the seventh opening and extending at an angle to the second opening along the incident direction of the film formation material in the second film formation.

11. 10. The method for manufacturing a Josephson junction element according to claim 9, wherein the step of forming the mask layer includes forming the mask layer having a fifth mask pattern including a ninth opening located in a fifth region that is at an angle of 45° to the second region with respect to the center of the substrate, the ninth opening extending obliquely relative to the first opening along the incident direction of the film formation material in the first film formation, and a tenth opening intersecting the ninth opening and extending obliquely relative to the second opening along the incident direction of the film formation material in the second film formation.

12. 10. The method for manufacturing a Josephson junction device according to claim 9, wherein the second film deposition from the second oblique direction is a film deposition from a direction that is different by 90 degrees with respect to the substrate from the first oblique direction.

13. forming a Josephson junction device; forming a capacitor connected in parallel to the Josephson junction device; The step of forming the Josephson junction device includes: forming a mask layer on a substrate; forming a first superconducting film on the substrate by first film deposition from a first oblique direction with respect to the substrate using the mask layer as a mask; forming an insulating film on a surface of the first superconducting film; and forming a second superconducting film having a region overlapping the first superconducting film via the insulating film by a second film formation from a second oblique direction different from the first oblique direction on the substrate using the mask layer as a mask, The step of forming the mask layer includes forming the mask layer having a first mask pattern located in a first region of the substrate and including a first opening extending along an incident direction of a film-forming material in one of the first film formation and the second film formation and a second opening extending in a direction intersecting the first opening, and a second mask pattern located in a second region of the substrate and including a third opening extending obliquely with respect to the first opening along the incident direction of a film-forming material in the one of the film formations and a fourth opening extending in a direction intersecting the third opening, the second region being closer to an edge of the substrate than the first region. How quantum bits are manufactured.

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