JPH05243627A - Josephson device and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a Josephson device, which can be manufactured without lifting off a resist stencil, by joining two superconducting films with an insulating film between on a junction-forming post. CONSTITUTION:A substrate 1 is provided with a groove 7 and a junction-forming post 8. The groove 7 has a depth of t1 and a width of 11, while the post 8 has a height of t1, a width of 12 and a length of w, where 11<12. A first superconducting film 2, an insulating film 41 and a second superconducting film 3 are formed by deposition at angles shown by arrowheads 1', 2' and 3', respectively. When the angles 1' and 2' satisfy a given relation, the first and second superconducting films are joined with the insulating film 41 between only in the post 8, thus forming an SIS junction 51. Therefore, a Josephson device with a very small junction area is provided without the need for lithography, including a lift-off step, after the film forming and junction forming.

Description

Detailed Description of the Invention

The present invention relates to a Josephson device and its manufacturing method.

[0002]

2. Description of the Related Art Lithography technology is indispensable for producing minute Josephson junctions. The most simplified method for forming the junction is the sampled resist stencil method (SPS method) shown in FIGS.
According to this method, first, as shown in FIG. 9, a stencil mask 6 which is partially hollow is prepared. Thereafter, as shown in FIG. 10 (this is a cross section taken along the line AA ′ in FIG. 9), the first and second superconducting films 2 and 3 and the normal conducting film 42 are formed on the substrate 1.
The SNS junction 52 can be formed by forming the films in the directions of arrows and. Also, SIS bonding or the like can be made by the same method.

[0003]

Although the method of adjusting the degree of self-alignment by the film-forming angle is very simple, it is usually a three-layer resist processing technique for forming a hollow resist stencil. Need. Moreover, since lift-off of the resist stencil is required, it is not suitable for joining lead-based alloys and oxide superconductors, which are easily deteriorated by organic solvents and water. Further, since all the ordinary organic resist stencils are burned on the substrate due to the high temperature environment during the film formation of the oxide superconductor, it is impossible to use such a material as an electrode by this method.

An object of the present invention is to provide a Josephson device and a method of manufacturing the same that solve the above problems.

[0005]

According to the Josephson element of the present invention, a junction forming pillar is provided in a groove formed on a substrate, and the first and second superconducting films formed on the junction forming pillar are The bonding columns are joined together via an insulating film.

Further, according to the present invention, the first and second superconducting films can be joined together via the normal conducting film.

Further, according to the present invention, the first and second superconducting films can be bonded together through the grain boundaries.

The method of manufacturing the Josephson device of the present invention is as follows.
A first superconducting film is provided on a substrate having grooves and junction forming columns.
A film is formed discontinuously at the groove portion and at a film forming angle so as to be formed on the bonding formation column upper portion, and then a second superconducting film is formed discontinuously at the groove portion. In addition, the film is formed at a film forming angle such that the film is formed so as to overlap with the first superconducting film in the portion of the bonding formation pillar.

Further, according to the present invention, after forming the first superconducting film, an insulating film is formed on the junction forming pillar.

Further, according to the present invention, after forming the first superconducting film, a normal conducting film is formed with a film forming angle capable of forming a film on the junction forming pillar.

[0011]

The operation of the present invention will be described first with reference to FIGS. 5 is a cross-sectional view of the groove 7 (depth t ₁ , width l ₁ ) formed in the substrate 1, and FIG. 6 is a junction forming column 8 (height t ₂ , width l ₂ , it is a cross-sectional view of l _2> l _1).

As shown in FIGS. 5 (a) and 6 (a),
First, the first superconducting film 2 is formed on the groove 7 and the junction forming pillar 8 at a film forming angle of θ ₁ .

Next, as shown in FIGS. 5B and 6B, the bonding film 4 is formed substantially perpendicular to the substrate.

Next, as shown in FIGS. 5C and 6C, the second superconducting film 3 is formed with a film forming angle of θ ₂ . If we consider a symmetric system where θ ₁ = θ ₂ = θ,

[Equation 1]

[0015]

When the film is formed with θ satisfying the condition of: A device in which the first and second superconducting films 2 and 3 are Josephson-coupled is obtained. The Josephson junction is shown at 5. Width l
_The joint area can be controlled by defining the area of the joint forming column 8 having ₂ . If the bonding film 4 is an insulator, SIS bonding can be made, and if it is a normal conductor, SNS bonding can be made.

7 and 8 show the case where the formation of the bonding film is omitted. 7 and 8 are almost the same as FIGS. 5 and 6, but in the case of an oxide superconductor having a short coherence length,
Even in such a structure, the Josephson device can be formed through the crystal interface.

[0018]

EXAMPLES Examples of the present invention will be shown below. (Embodiment 1) FIGS. 1 and 2 are perspective views showing a first embodiment of the present invention. 1 is a perspective view of the substrate 1, and FIG. 2 is a perspective view showing a state in which a Josephson junction is formed on the substrate 1. Hereinafter, a method for manufacturing the Josephson junction of this embodiment will be described.

First, as shown in FIG. 1, a substrate 1 having a groove 7 and a junction forming pillar 8 is prepared. The groove 7 has a depth t ₁ and a width l ₁
And the joint forming column 8 has a height t ₂ , a width l ₂ and a length w, and l ₁ ≦ l ₂ .

Next, as shown in FIG. 2, the first superconducting film 2, the insulating film 41, and the second superconducting film 3 are formed at the film forming angles indicated by arrows and. If the film forming angles indicated by and satisfy the expression 1, the first and second
The superconducting films 2 and 3 are bonded to each other only through the insulating film 41 on the junction forming pillar 8 to form the SIS junction 51. Further, the insulating film 41 can be formed by a means such as utilizing a surface thermal oxide film without forming the above-mentioned film. (Embodiment 2) FIG. 3 is a perspective view showing a second embodiment of the present invention. The structure and manufacturing method of this embodiment are almost the same as those of the first embodiment. The difference is that instead of the insulating film 41 of FIG. 2, a normal conductive film 42 is formed in the direction of the arrow in this embodiment. Therefore, the Josephson device of the SNS junction 52 coupled by the proximity effect is obtained. (Embodiment 3) FIG. 4 is a perspective view showing a third embodiment of the present invention. The structure and manufacturing method of this embodiment are almost the same as those of the first embodiment. The difference is that the insulating film 41 is formed in FIG. 2, but this is omitted in this embodiment. That is, the first superconducting film 2 and the second superconducting film 3 are in direct contact with each other. When the first and second superconducting films are made of, for example, an oxide high-temperature superconductor, a grain boundary is generated at the contact portion between the first and second superconducting films, and the grain boundary junction 53 is formed through the grain boundary. You can make a Josephson device.

[0021]

As described above, according to the present invention, it is possible to obtain a Josephson device having a fine junction area which does not require any lithography process including a lift-off process after film formation and after junction formation. Have an effect.

[Brief description of drawings]

FIG. 1 is a perspective view of a substrate provided with a groove and a bonding formation pillar.

FIG. 2 is a perspective view showing a first embodiment of the present invention.

FIG. 3 is a perspective view showing a second embodiment of the present invention.

FIG. 4 is a perspective view showing a third embodiment of the present invention.

FIG. 5 is a diagram for explaining the operation of the present invention.

FIG. 6 is a diagram for explaining the operation of the present invention.

FIG. 7 is a diagram for explaining the operation of the present invention.

FIG. 8 is a diagram for explaining the operation of the present invention.

FIG. 9 is a schematic view showing a conventional manufacturing method.

FIG. 10 is a schematic view showing a conventional manufacturing method.

[Explanation of symbols]

 1 Substrate 2 First Superconducting Film 3 Second Superconducting Film 4 Bonding Film 5 Josephson Junction 6 Stencil Mask 7 Groove 8 Bonding Groove 41 Insulating Film 42 Normal Conductive Film 51 SIS Bonding 52 SNS Bonding 53 Grain Boundary Bonding

Claims (6)

[Claims] 1. A junction formation pillar is provided in a groove formed on a substrate, and first and second superconducting films formed on the junction formation pillar are bonded via an insulating film in the junction formation pillar. Josephson device doing. 2. A junction forming column is provided in a groove formed on a substrate, and the first and second superconducting films formed on the junction forming column are formed on the junction forming column via a normal conductive film. Josephson device coupled. 3. A junction forming pillar is provided in a groove formed on a substrate, and the first and second superconducting films formed on the junction forming pillar are formed on the joining forming pillar via a grain boundary. Josephson device coupled. 4. A first superconducting film is formed on a substrate provided with a groove and a junction forming pillar, discontinuously at the groove portion and above the junction forming pillar portion. A second superconducting film is formed at a film forming angle, and then a second superconducting film is formed discontinuously at the groove portion and overlapping the first superconducting film at the junction forming pillar portion. A method of manufacturing a Josephson device in which a film is formed at an angle. 5. The method of manufacturing a Josephson junction according to claim 4, wherein after forming the first superconducting film, an insulating film is formed on the junction forming pillar. 6. The method for manufacturing a Josephson device according to claim 4, wherein after forming the first superconducting film, a normal conducting film is formed with a film forming angle capable of forming a film on the junction forming pillar.