JPH0652810B2 - Superconducting circuit device - Google Patents

Description

The present invention relates to a superconducting circuit device, and more particularly to a superconducting circuit device having a superconducting tunnel barrier.

A superconducting circuit device having a superconducting tunnel barrier is described, for example, in the document Proceeding of the AI Magazine.
ings of the IEEE) Vol.55 No.2 February 1967 PP.172-18
0 or well known as shown in USP 4334158.

FIGS. 1 (a) and 1 (b) are views for explaining one of conventional examples of a superconducting circuit device. In FIG. 1 (a), a superconducting base electrode 2 is formed on a substrate 1, an insulating layer 3 is used on the surface of the superconducting base electrode 2 to define a region of a tunnel barrier 4, and the superconducting portion is in contact with the tunnel barrier 4. The counter electrode 5 is formed. Fig. 1
In (b), the first superconducting electrode 7 is formed on the substrate 6, the region of the first tunnel barrier 8 is defined by using the insulating layer 9 on the surface thereof, and the first superconducting electrode 7 is in contact with the first tunnel barrier 8. A second superconducting electrode 10 is formed on the portion and the second superconducting electrode 1 is further formed.
The second tunnel barrier 11 using the insulating layer 12 on the surface of
And a third superconducting electrode 13 is formed in a portion in contact with the second tunnel barrier 11.

As shown in the above two examples, in the conventional superconducting circuit device using the tunnel barrier, each superconducting electrode except the first superconducting electrodes 2 and 7 and the insulating layer exceed the stepped portion generated in each underlayer. Since the structure is formed as described above, discontinuity of each of the superconducting electrodes and the insulating layer is likely to occur at the step portion, and the yield and reliability of the device are likely to be deteriorated. or,
In order to secure the continuity of each of the superconducting electrodes or insulating layers at the step, there is a limitation in manufacturing the device that the film thickness of each should be thicker than the step that they should pass. . Furthermore, during the thermal cycle between room temperature and 4.2 ° K, due to the difference in the thermal expansion coefficient between the substrate and the superconducting electrode, compressive stress or tensile stress is generated in the superconducting electrode in the direction parallel to the substrate, resulting in tunneling. A so-called hillock that hits the barrier occurs, which may cause deterioration of the tunnel barrier, for example, in the literature IE Transaction on Electron Device Magazine.
n Device) ED-27 No.10 PP.1979-1987 1980.

FIG. 2 is a diagram for explaining another conventional example of a superconducting circuit device. In FIG. 2, a superconducting base electrode 15 is provided on a substrate 14, an insulating layer 16 is provided on the main surface excluding the side surface thereof, and a tunnel barrier 17 is provided on the side surface of the superconducting base electrode 15. A counter electrode 18 is provided in contact with the tunnel barrier 17.

In the conventional superconducting circuit device using the tunnel barrier shown in the above example, since the counter electrode 18 is formed beyond the step portion formed in the base, the counter electrode 18 is apt to cause discontinuity in the step portion. The structure was likely to cause a decrease in yield and reliability.

The present invention has been made in view of the above structural defects, and at least the first superconductor and the second superconductor are provided on a required substrate.
Of the superconductor of the same thickness as each of the superconductors so that each of the superconductors is in contact with the side surface of the superconductor through the tunnel barrier and is in contact with and surrounds the side surface of each of the superconductors. It is characterized by a planar structure in which the layers are provided in the same layer and the device main plane is in the same plane.

The present invention will be described below with reference to the drawings. First, the principle of the present invention will be described with reference to FIG. As shown in FIG. 3, the basic structure of the superconducting circuit device according to the present invention is such that a first superconducting electrode 20, a second superconducting electrode 22 and an insulating layer 23 are provided on a required substrate 19 to form a first superconducting electrode. The side surfaces of the conduction electrode 20 and the second superconducting electrode 22 are in contact with each other via the tunnel barrier 21, and the side surfaces of the first superconducting electrode 20 and the second superconducting electrode 22 which are not in contact with the tunnel barrier are It has a planar structure in contact with the insulating layer 23. As a result, it is possible to obtain a new structure capable of eliminating the stepped portion that must be crossed by the superconducting electrode and the insulating layer. Therefore, the continuity of the superconducting electrode and the insulating layer is improved. Also, the thickness of the insulating layer and the second
The thickness of the superconducting electrode can be independently determined without depending on the height of the step. In this case, the insulating layer, the first superconducting electrode, and the second superconducting electrode are made equal in thickness in order to flatten the base of the wiring portion. Room temperature and 4.2 °
Even if a compressive stress or a tensile stress is generated in the direction parallel to the substrate in the superconducting electrode due to the difference in the thermal expansion coefficient between the substrate and the superconducting electrode during the thermal cycle between K, the tunnel barrier will be in the direction of the force. On the other hand, since it is provided in a plane that is substantially vertical, it is possible to prevent the deterioration of the tunnel barrier due to the generation of so-called hillocks that hit the tunnel barrier.

Further, the present invention can realize a high yield and high reliability in a superconducting circuit device using a tunnel barrier and easily realize a device having a multilayer structure.

Next, in order to better understand the present invention, examples will be described. FIG. 4 shows a cross-sectional structure of a Josephson device circuit as an embodiment of the present invention. In the figure, the ground plane layer 124 is provided on the substrate 24 by using, for example, Nb. An insulating layer 22 is formed on the insulating layer 22 by using, for example, SiO or Nb ₂ O _5.
4 are provided. Although the ground plate layer 124 and the insulating layer 224 are not always necessary, this embodiment shows a structure using them in order to realize appropriate device parameters. In contact with the insulating layer 224, for example, Nb
Then, the insulating layer 28 is provided with substantially the same thickness using the first superconducting electrode 25, the second superconducting electrode 27, and Nb ₂ O _5, for example. First superconducting electrode 25 and second superconducting electrode 2
7 is arranged in parallel with the substrate through a tunnel barrier 26, and is surrounded by an insulating layer 28 in contact with the periphery.
The connection of each element is performed by the connection line 29. In this case, since the main surface of the device constituted by the first and second superconducting electrodes and the insulating layer is almost flat, the continuity of the continuous line 29 is good. FIG. 5 shows a circuit sectional structure including an element using two or more superconducting tunnel barriers as another embodiment of the present invention. In the figure, the ground plane layer 130 is provided on the substrate 30 by using, for example, Nb. An insulating layer 230 is provided thereon by using, for example, SiO or Nb ₂ O ₅ . Although the ground plate layer 130 and the insulating layer 230 are not always necessary, this embodiment shows a structure using them in order to realize appropriate device parameters. The insulating layer 36 is in contact with the insulating layer 230 and is made of, for example, Nb. The first superconducting electrode 31, the second superconducting electrode 33, the third superconducting electrode 35 and, for example, Nb ₂ O ₅ are used to form the insulating layer 36 having substantially the same thickness. It is provided by The first superconducting electrode 31 and the second superconducting electrode 33 are arranged in parallel to the substrate via the tunnel barrier 32, and the second superconducting electrode 33 and the third superconducting electrode 35 further form the tunnel barrier 34. The side surfaces of the first, second and third superconducting electrodes which are arranged parallel to the substrate and are not in contact with the tunnel barriers are surrounded by the insulating layer 36. The connection of each element is performed by the connection line 37. In this case, since the main surface formed by the first, second and third superconducting electrodes and the insulating layer is substantially flat, the continuity of the connecting line 37 is good.

As is apparent from the above description of the embodiments, the feature of the present invention is that the superconducting electrodes that are in contact with each other through the tunnel barrier are arranged on the substrate in contact with each other in the direction parallel to the substrate. A superconducting circuit device having a planar structure in which the side surface is surrounded by an insulating layer.

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) are structural cross-sectional views of a superconducting circuit device for explaining a conventional technique. FIG. 2 is a structural sectional view of a superconducting circuit device for explaining a conventional technique. FIG. 3 is a structural sectional view of a superconducting circuit device for explaining the principle of the present invention. FIG. 4 is a structural sectional view of a Josephson device circuit for explaining an embodiment of the present invention. FIG. 5 is a structural sectional view of a circuit including an element using two or more superconducting tunnel barriers for explaining another embodiment of the present invention. In the figure, 1, 6, 14, 19, 24 and 30 are substrates, 2, 7, 15, 20, 25 and 31 are first superconducting electrodes, 3, 9, 12, 16, 23, 28, 36 is an insulating layer, 4,8,11,17,21,26,32 and 34 are tunnel barriers 5,10,18,22,27 and 33 are second superconducting electrodes, 13 and 35 are third superconducting electrodes. Conductive electrode, 12
4 and 130 are ground plane layers, 224 and 230 are insulating layers,
Reference numerals 29 and 37 are connection lines.

Claims (1)

[Claims] 1. At least a first superconductor and a second superconductor are provided on a required substrate, each superconductor being in contact with its side surface through a tunnel barrier, and said superconductor. A superstructure characterized by a planar structure in which an insulating layer having the same thickness as each superconductor is provided in the same layer so as to surround and contact the other side surface of each superconductor, and the main plane of the device is in the same plane. Conduction circuit device.