JPH08340133A - Contact structure between superconductive layers and method of manufacturing the same - Google Patents

Abstract

PURPOSE: To provide the title contact structure between superconductive layers and method of manufacturing the same capable of realizing the reduction of the contact area of said contact structure using edge junction step. CONSTITUTION: The first superconductive layer 11 is processed by ion beam edging step making beam incident angle of 30 deg. so as to form an edge 16 making a gentle oblique angle of 7 deg.' and another edge 17 making a steep oblique angle of 30 deg.. In such a constitution, an edge junction part 18, i.e., the Josephson coupling made of the first superconductive layer 11 and the second superconductive layer 12 loosely coupled with each other is composed in the edge 16 through the intermediary of a tunnel barrier 15. Likewise, in the edge 17, another edge junction part 19 made of the first superconductive layer 11 and the second conductive layer 12 coupled with each other is composed, however, due to the steep oblique angle in the edge 17, the coverage of the first superdonductive layer 11 by the tunnel barrier 15 is made narrower thereby enabling excellent contact part to be composed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact structure between superconducting layers and a method of manufacturing the same, and more particularly to a structure of a contact between high-temperature superconducting layers in a circuit using a high-temperature superconductor and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a contact structure between high-temperature superconducting layers in a conventionally known high-temperature superconducting circuit having a multi-layer structure, it is general to form a contact hole in an interlayer insulating layer (for example, an applied structure). Physics Letters, Vol. 59, p. 3051, 1991).

FIG. 4 is a sectional view showing an example of the conventional contact structure between high temperature superconducting layers. As shown in FIG. 1, the first superconducting layer 11 and the second superconducting layer 12 on the substrate 10 have a structure in which an interlayer insulating layer 13 is interposed. The superconducting contact between the second superconducting layers 12 is performed by opening a contact hole 14 in the interlayer insulating layer 13 and then bringing the first superconducting layer 11 and the second superconducting layer 12 into direct contact therewith. .

Further, conventionally, as shown in the sectional view of FIG. 5, a contact hole is formed at a depth including the first superconducting layer 11, and a contact is made by using an inclined surface of the edge of the first superconducting layer 11. Has been proposed (Japanese Patent Laid-Open No. 2-7)
No. 7177). That is, according to this conventional contact structure, as shown in FIG. 5, in the electrical contact portion provided in the oxide superconducting layer wiring extending in the ab plane, the contact hole 14 and the interlayer insulating layer 12 are formed. This is a structure in which the first superconducting layer 11 is opened, and the second superconducting layer 12 is brought into contact with the ab plane of the first superconducting layer 11 at a plane obliquely cut.

[0005]

However, the above conventional contact structure requires at least a contact hole patterning step and a processing step, and the process is complicated.

In a high-temperature superconducting circuit, a Josephson junction called an edge junction is often used. FIG. 6 shows a cross-sectional view of this edge bond. As shown in the figure, this edge junction processes the lower electrode 21 together with the interlayer insulating layer 23 thereabove to expose the edge 24 of the lower electrode 21, and at this edge 24, a tunnel barrier made of a normal conductor or an insulator is formed. 25
It is a Josephson junction of a type in which the upper electrode 22 is formed via the and the Josephson effect is generated between the lower electrode 21 and the upper electrode 22.

Even in a circuit using this edge joining,
In some cases, a contact for superconducting a short circuit between the lower electrode 21 and the upper electrode 22 is required. In this case, since the lower electrode 21 and the upper electrode 22 are on the same plane, the contact between the lower electrode 21 and the upper electrode 22 must necessarily be provided with the contact hole 14 in the conventional contact structure shown in FIGS. There is a feature that there is no.

However, in order to prevent contamination at the interface of the tunnel barrier 25, the tunnel barrier 25 and the upper electrode 2 are usually used.
2 has continuous film formation and continuous processing, and therefore a tunnel barrier 25 exists between the lower electrode 21 and the upper electrode 22, and a contact for the tunnel barrier 25 is made in the case of a contact on a plane or a contact on a gentle slope. The critical current density is extremely small, and a wide contact area is required to obtain the required critical current density.

If the slope of contact hole 14 shown in FIG. 5 is steep, the superconducting characteristics of second superconducting layer 12 at the portion introduced into contact hole 14 are reduced, and as a result, contact hole 14 Critical current density decreases. Therefore, also in this case, a large contact area is required. In many cases, high-temperature superconducting integrated circuits must have as small an inductance as possible, which makes the above-mentioned need for a large contact area a serious problem in circuit construction.

The present invention has been made in view of the above points,
An object of the present invention is to provide a contact structure between superconducting layers and a method for manufacturing the same, which can reduce the contact area of the contact structure between the superconducting layers using the edge junction and simplify the process.

[0011]

In order to achieve the above object, the present invention achieves the above object by providing a first superconducting layer formed on a first edge with a tunnel barrier made of a normal conductor or an insulator. Forming a second edge in the first superconducting layer, the second superconducting layer having a bonded edge junction, and a second edge having a steeper inclination angle than the first edge forming the edge junction; On the edge of the second superconducting layer.

Further, according to the present invention, the first and second edges are:
It is characterized in that each is formed on the opposite side of the first superconducting layer.

Further, the present invention is configured such that the film thickness of the tunnel barrier on the second edge is formed thinner than the film thickness of the tunnel barrier on the first edge.

According to a fourth aspect of the present invention, in the method for manufacturing a contact structure, a first superconducting layer and an interlayer insulating layer are sequentially laminated on a substrate, and a first superconducting layer and an interlayer insulating layer are formed in a predetermined region on the interlayer insulating layer. With the substrate on which the resist mask is formed being fixed, ion beam irradiation is performed by irradiating an ion beam from obliquely above, and the first and second layers having different inclinations from each other are formed on the interlayer insulating layer and the first superconducting layer. A first step of forming the edge of the first and the first step formed by the first step
And a second step of continuously forming a tunnel barrier layer and a second superconducting layer made of a normal conductor or an insulator on the second edge and the interlayer insulating layer; and at least the first and second edges. And a third step of performing continuous processing so that the tunnel barrier layer and the second superconducting layer are arranged in the portion.

Here, the second step includes the first and second steps.
Of the substrate in such a direction that the thickness of the tunnel barrier growing on the second edge of the steeply inclined edge becomes smaller than the thickness of the tunnel barrier growing on the first edge of the gentle slope. Adjusting the angle to grow the tunnel barrier is desirable in that the thickness of the tunnel barrier on the steeply inclined second edge can be reduced.

[0016]

[Function] In the case of the contact between the lower electrode and the upper electrode of the edge junction, there is a tunnel barrier between the contacts on the plane or on the gentle slope, so that the critical current density of the contact is equal to or lower than that of the edge junction. become. However, when the lower electrode and the upper electrode are in contact with each other on a surface having a steeper slope than the edge forming the edge junction, the tunnel barrier is usually 50 nm or less, which is sufficiently thinner than the typical thickness of the lower electrode of 300 nm. Therefore, the coverage of the lower electrode surface with the tunnel barrier is lower than that of the edge junction.

For this reason, there are places where the lower electrode and the upper electrode are in direct contact with each other and where the tunnel barrier is thinner than other parts. The critical current density when the high-temperature superconducting layers are completely bonded without a barrier reaches 100 to 1000 times the critical current density of the edge junction. Therefore, the critical current density of the contact increases dramatically in these portions.

According to the first aspect of the present invention, a second edge having a steeper inclination angle than the first edge forming the edge junction is formed in the first superconducting layer, and the second edge is formed on the second edge. Since the two superconducting layers are arranged, the critical current density of the contact can be dramatically increased at the contact portion with the second superconducting layer on the second edge of the first superconducting layer. .

In the edge joining, as shown in FIG. 6, a lower electrode 21 is provided on a substrate 20, an interlayer insulating layer 23 is further provided on the lower electrode 21, and a gentle edge 24 formed on these is formed. The upper electrode 22 is formed on the upper surface of the lower electrode 2 with a tunnel barrier 25 interposed therebetween.
1 and the upper electrode 22 are on the same plane. Therefore, there is no need to provide a contact hole as in the conventional contact structure, and a contact can be formed by arranging the upper electrode 22 on the edge 24 of the lower electrode 21 as in the case of the edge junction. At this time, if the slope of the edge serving as the contact portion is steeper than the slope of the edge joint, the above effect can be expected.

In the formation of the edge junction shown in FIG. 6, the high temperature superconducting thin film of the lower electrode 21 is etched by obliquely irradiating the ion beam with the substrate 20 fixed, and an edge having a desired inclination is formed. Form. Fig. 3 shows the incident angle of the ion beam and the typical high-temperature superconductor, yttrium, barium, and copper oxide.

[0021]

[Outside 1] The relationship with the inclination angle of the edge actually formed is shown in "YBCO" below.

The angle shown in FIG. 3 is an angle measured from the substrate, and the normal direction of the substrate is 90 °. The characteristic I indicated by a circle is the inclination angle on the side where the edge is shaded by the resist mask from the ion beam. Since a relatively gentle inclination angle is obtained, the edge junction is formed on this side edge.
On the other hand, the characteristic II of the square mark is the inclination angle of the edge that is not hidden from the ion beam by the resist mask on the opposite side. In the typical case, the characteristic II of the edge inclination angle of 7 ° at the ion beam incident angle of 30 ° is used for the edge junction. At this time, the inclination angle on the opposite side (characteristic I) is about 30 °, which is steeper than that at the edge joint.

Further, by adjusting the substrate angle in a direction in which the tunnel barrier grows thinner than the edge forming the edge junction with the edge forming the contact, and growing the tunnel barrier, the tunnel barrier to the lower electrode at the contact portion is formed. Can be further reduced.

From the above, in a circuit having an edge junction, by forming a contact on a steeper edge opposite to the edge junction and adjusting a substrate angle at the time of forming a tunnel barrier, the lower electrode And the superior superconducting contact having a high critical current density can be obtained without providing a contact hole.

[0025]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view showing one embodiment of a contact structure between superconducting layers according to the present invention. A first superconducting layer 11 which is a lower electrode of an edge junction is formed on a substrate 10 to a thickness of 300 nm. The first superconducting layer 11 is processed by ion beam etching at a beam incident angle of 30 °, in which a gentle edge 16 with an inclination angle of 7 ° is formed on the left side and a steep edge with an inclination angle of 30 ° on the right side. 17 are formed.

A second superconducting layer 12 which is an upper electrode of an edge junction is formed on each edge 16 and 17 through a tunnel barrier 15 having a film thickness of 20 nm in a flat portion.
It is formed with a film thickness of 00 nm. Further, the interlayer insulating layer 13 is formed on the first superconducting layer 11. Here, the first and second superconducting layers 11 and 12 are made of YBCO
The substrate 10 and the interlayer insulating layer 13 are made of strontium titanate (SrTiO ₃ , hereinafter, referred to as “STO”). The tunnel barrier 15 is made of praseodymium / barium / copper oxide

[0027]

[Outside 2] However, other normal conductors such as normal YBCO and ST
An insulator such as O can also be used.

The edge 16 has an edge junction 18 in which the first superconducting layer 11 and the second superconducting layer 12 are loosely coupled via the tunnel barrier 15, that is, a Josephson junction. On the other hand, the tunnel barrier 1 is also on the edge 17.
An edge junction 19 in which the first superconducting layer 11 and the second superconducting layer 12 are coupled via the junction 5, ie, a Josephson junction, is formed. The coverage of the first superconducting layer 11 by the tunnel barrier 15 is low, and the superconducting critical current density between the first superconducting layer 11 and the second superconducting layer 12 is
It is much larger than 8. Therefore, the edge joint portion 19 constitutes a good contact portion.

Next, a method of manufacturing the contact structure between the superconducting layers according to the present invention will be described. FIG. 2 is a process explanatory view of one embodiment of a method for manufacturing a contact structure between superconducting layers according to the present invention. In this embodiment, in FIG. 2A, a first superconducting layer 11 made of YBCO and an interlayer insulating layer 13 made of STO are respectively laminated on a substrate 10 made of STO to a thickness of 300 nm. Insulation layer 1
A resist mask 30 is provided in a predetermined area on the substrate 3.

When the substrate 10 having this structure is fixed and, for example, an argon (Ar) ion beam 31 is irradiated under the condition of an ion beam incident angle of 30 ° as shown in FIG. The interlayer insulating layer 13 that directly collides without passing through the first superconducting layer 11 and the first superconducting layer 11 thereunder are scraped off by the impact at the time of the collision as shown in FIG. An edge 17 is formed.

On the other hand, due to the existence of the resist mask 30, the interlayer insulating layer 13 is formed in the shadow of the resist mask 30.
As shown in FIG. 2B, a gentle (sloping angle 7 °) edge 16 is formed in the first superconducting layer 11 thereunder.

Subsequently, after the resist mask 30 is removed by a known means, the thickness of the flat portion is reduced to 20 by vapor deposition or the like.
The thickness of the tunnel barrier 15 and the flat portion is 4 nm.
A second superconducting layer 12 having a thickness of 00 nm is continuously formed. Then, as shown in FIG. 2C, the second superconducting layer 12 and the tunnel barrier 15 are continuously processed by ion beam etching.

At this time, the first on the gentle edge 16
Since the tunnel barrier 15 exists between the superconducting layer 11 and the second superconducting layer 12, the edge junction 18 is formed. On the other hand, on the edge 17 having a steeper slope than the edge 16 forming the edge junction 18, the first superconducting layer 11 is formed.
The tunnel barrier 15 between the second superconducting layer 12 and
nm and the film thickness of the first superconducting layer 11 is sufficiently smaller than 300 nm, the coverage of the surface by the tunnel barrier 15 is reduced, and therefore the first superconducting layer 11 and A contact portion 19 having a large critical current density between the two superconducting layers 12 can be formed. Thus, the contact structure having the cross-sectional structure shown in FIG. 1 is manufactured.

When the substrate 10 is turned clockwise, for example, by 45 ° in FIG. 2B when the tunnel barrier 15 is formed, the edge 16 which becomes the edge joint portion 18 faces the evaporation source, but the contact Since the partial edge 17 is shaded from the vapor deposition source, the film thickness of the tunnel barrier 15 on the edge 17 can be made to be thinner than the film thickness on the edge 16, and thus the tunnel barrier on the edge 17 can be grown. The coverage of the first superconducting layer 11 with 15 can be further reduced. As a result, the critical current density at the edge junction 19 serving as a contact is further improved.

As described above, according to this embodiment,
In the circuit using the edge junction, the steep slope on the opposite side of the edge junction can be used as the contact portion. In this embodiment, since it is not necessary to open a contact hole, the process is simple. Further, the contact area can be significantly reduced as compared with the case where a contact hole is provided.

[0036]

As described above, according to the present invention,
A gentle edge and a steep edge are formed in the first superconducting layer, and the thickness of the tunnel barrier formed on the first superconducting layer can be reduced on the steep edge. The coverage of the tunnel barrier can be reduced, so that an excellent contact portion between the first and second superconducting layers having a high critical current density can be formed on the steep edge, and this contact portion is formed as a contact hole. Can be obtained without providing Therefore, according to the present invention, the process is simplified as compared with the case where a contact hole is used, and the contact area is reduced, so that the circuit area can be reduced and the circuit inductance can be reduced.

[Brief description of drawings]

FIG. 1 is a structural sectional view of an embodiment of the present invention.

FIG. 2 is a process explanatory view of one embodiment of the production method of the present invention.

FIG. 3 is a diagram illustrating the dependence of the YBCO edge tilt angle on the ion beam incident angle for explaining the operation of the present invention.

FIG. 4 is a structural cross-sectional view of an example of the related art.

FIG. 5 is a structural sectional view of another conventional example.

FIG. 6 is a cross-sectional view of an edge joint for explaining a problem to be solved by the invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 11 1st superconducting layer 12 2nd superconducting layer 13 Interlayer insulating layer 15 Tunnel barrier 16 Gentle edge 17 Steep edge 18 Edge joining part 19 Contact part 30 Resist mask 31 Ion beam

Claims (5)

[Claims] A first superconducting layer having an edge junction formed on a first edge formed on the first superconducting layer via a tunnel barrier made of a normal conductor or an insulator; A second edge having a steeper inclination angle than the first edge forming the edge junction is formed by the first edge.
And a second superconducting layer disposed on the second edge, the contact structure between the superconducting layers. 2. A contact structure between superconducting layers according to claim 1, wherein said first and second edges are formed on opposite sides of said first superconducting layer, respectively. 3. The tunnel barrier according to claim 1, wherein a thickness of the tunnel barrier on the second edge is smaller than a thickness of the tunnel barrier on the first edge. Contact structure between superconducting layers. 4. A state in which a first superconducting layer and an interlayer insulating layer are sequentially laminated on a substrate, and the substrate on which a resist mask is formed in a predetermined region on the interlayer insulating layer is fixed, A first step of irradiating an ion beam from obliquely above to perform ion beam etching to form first and second edges having different inclinations on the interlayer insulating layer and the first superconducting layer, respectively. A second barrier layer formed of a normal conductor or an insulator and a second superconducting layer are continuously formed on the first and second edges formed in the first step and the interlayer insulating layer. And a third step of performing continuous processing so that the tunnel barrier layer and the second superconducting layer are arranged in a portion including at least the first and second edges. Contour between superconducting layers Manufacturing method of the door structure. 5. The method according to claim 5, wherein the thickness of the tunnel barrier layer growing on the second edge of the first and second edges, which is steeply inclined, is gradually increased. 5. The superconducting device according to claim 4, wherein the growth of the tunnel barrier layer is performed by adjusting an angle of the substrate so as to be thinner than a film thickness of the tunnel barrier layer growing on the first edge. A method for manufacturing an interlayer contact structure.