JPH05152617A - Superconducting shield layer - Google Patents

Abstract

PURPOSE:To obtain a shield layer which prevents interference between signals and does not lower the degree of integration by successively forming oxide layers and oxide superconductor crystal layers having similar crystal structures on an oxide superconductor. CONSTITUTION:After forming a Y1Ba2Cu3O7-x film on an MgO substrate 5 as a ground plane 4 and another MgO film on the ground plane 4 as an insulating layer 21, a Y1Ba2Cu3O7-x thin film is formed as a first wiring layer 11 and the layer 11 is processed. Then an MgO film is formed on the layer 11 as an insulating layer 22 and a superconducting shield layer 3 is formed on the layer 22. The layer 3 is formed in such a way that, after a Pr1Ba2Cu3O7-x thin film having a film thickness of about 5nm (four unit lattices) is formed on the layer 22 as a first oxide layer 32, a Y1Ba2Cu3 O7-x thin film having a film thickness of about 2nm (two unit lattices) is formed on the layer 32 as an oxide superconductor crystal layer 31 and a second oxide layer 33 is formed on the layer 21 in the same way as that used for the layer 32. Then an MgO insulating layer 23 and superconducting wiring layer 12 are successively formed on the layer 33. When a superconducting current flows between the wiring layers 11 and 12, it can be confirmed that both layers 11 and 12 are electromagnetically shielded from each other by the Meissner effect of the layer 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting shield layer. More specifically, it relates to a superconducting shield layer used for superconducting multilayer wiring.

[0002]

2. Description of the Related Art Applications of superconductors to electronic equipment are roughly divided into two types. That is, a superconducting element that uses a superconductor and operates on a principle different from that of a conventional semiconductor element, and a superconducting wiring that uses a superconductor for an electric line in an electronic device. It is considered that by replacing the currently used semiconductor element with a superconducting element, it is possible to dramatically improve the performance of electronic equipment. The use of superconducting elements in combination with superconducting wiring gives a higher effect, while
It has been found that electronic devices can be speeded up only by superconducting wiring. In particular, when a superconducting conductive line is used as the signal line, it is possible to transmit a signal having a higher frequency than before, which leads to speedup of electronic equipment. Further, since signal attenuation is reduced, it is possible to reduce the number of amplifiers and the like, which has an effect of reducing power consumption.

On the other hand, in recent years, research on oxide superconductors having a high critical temperature has progressed, and oxide superconductors are being put to practical use in addition to conventional metal superconductors. There are many types of oxide superconductors, but a typical one has a critical temperature of 80K.
Before and after Y ₁ Ba ₂ Cu ₃ O _7-X oxide superconductor, critical temperature is 10
There are Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _y based oxide superconductors around 0 K and Tl ₂ Ba ₂ Ca ₂ Cu ₃ O _z based oxide superconductors with a critical temperature around 120 K. Both oxide superconductors have a critical temperature well above that of metallic superconductors.

[0004]

When the superconducting wiring of the above oxide superconductor is used in an integrated circuit, it is necessary to form a multilayer wiring with an oxide superconductor. When forming multilayer wiring with an oxide superconductor, an oxide superconducting thin film is formed on an appropriate substrate, this oxide superconducting thin film is processed into the shape of the desired wiring, and an insulating layer is formed thereon. Repeat the coating process.

On the other hand, in order to improve the degree of integration of the integrated circuit, it is necessary to reduce the wiring interval. When the wiring interval is reduced, interference of signals propagating between adjacent wirings becomes a problem. In particular, an integrated circuit using the above-mentioned superconducting multilayer wiring processes a high frequency and high speed signal, and therefore signal interference becomes a serious problem.

The above signal interference can be solved by providing a shield between the wirings. Therefore, an object of the present invention is to provide an effective shield layer that prevents the above-mentioned signal interference in a superconducting multilayer wiring using an oxide superconductor and does not reduce the degree of integration.

[0007]

According to the present invention, in an insulating layer which is arranged between a pair of superconducting wires and electrically insulates the superconducting wires, it extends parallel to at least one of the pair of superconducting wires. Similar to the existing oxide superconductor crystal layer having a thickness of several unit lattices and the oxide superconductor arranged on both sides of the oxide superconductor crystal layer in contact with the oxide superconductor crystal layer An oxide layer having a crystal structure of 1. is provided.

[0008]

[Operation] The superconducting shield layer of the present invention is arranged in an insulating layer between a pair of superconducting wirings, and an oxide superconducting crystal layer parallel to at least one of the superconducting wirings and having a thickness of several unit lattices. Its main feature is that it has an oxide layer having a crystal structure similar to that of the oxide superconductor, which is laminated on both sides of the oxide superconductor crystal layer. In the superconducting shield layer of the present invention, the oxide layer having a crystal structure similar to that of the oxide superconductor and the oxide superconductor crystal layer are laminated, so that the oxide superconductor crystal layer has a thickness of 1 unit lattice. If more than a minute, it shows superconductivity. Therefore, the shield layer can be inserted without substantially changing the thickness of the entire insulating layer. Further, the electromagnetic shield effect can be adjusted by the thickness of the oxide superconductor crystal layer.

The superconducting shield layer of the present invention functions as an electromagnetic shield due to the Meissner effect. Therefore, the oxide superconductor of the superconducting shield layer of the present invention must be in the superconducting state at the temperature at which the superconducting wiring is operating. Therefore, the critical temperature of the oxide superconductor used for the superconducting shield layer of the present invention is preferably equal to or higher than the critical temperature of the superconductor used for the superconducting wiring.

Although any oxide superconductor can be used for the superconducting shield layer of the present invention, for example, Y ₁ Ba ₂ Cu ₃ O _7-X ,
Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _x , Tl ₂ Ba ₂ Ca ₂ Cu ₃ O _{x and the} like can be stably produced and are excellent in characteristics, which is preferable. Further, in the oxide layers arranged on both sides of the oxide superconductor crystal conductor of the superconducting shield layer of the present invention, Pr ₁ Ba ₂ Cu ₃ O _7-y , Bi ₂ Sr ₂ Cu ₁ O are contained.
It is preferable to use ₆ or the like. The oxide layer is Pr ₁ Ba ₂ Cu ₃
It is preferable that a required number of crystal layers of oxides such as O _7-y and Bi ₂ Sr ₂ Cu ₁ O ₆ are laminated by the MBE method or the like.

Hereinafter, the present invention will be described in more detail by way of examples, but the following disclosure is merely examples of the present invention and does not limit the technical scope of the present invention.

[0012]

EXAMPLE FIG. 1 (a) shows a cross-sectional view of a superconducting multilayer wiring provided with a superconducting shield layer of the present invention. The superconducting multilayer wiring shown in FIG. 1 (a) is formed on the substrate 5, and includes the bottom ground plane 4 and the insulating layer 21 on the ground plane 4.
And the first superconducting wire 11, which is sequentially stacked on the insulating layer 21,
An insulating layer 22, a superconducting shield layer 3 of the present invention, an insulating layer 23 and a second superconducting wire 12 are provided. Also, superconducting wiring
Connection hole 6 for making electrical connection to both 11 and 12
It is equipped with.

FIG. 1 (b) shows an enlarged cross section of the superconducting shield layer 3 of the present invention used in the above superconducting multilayer wiring. As shown in FIG. 1 (b), the superconducting shield layer 3 of the present invention comprises an oxide superconductor crystal layer 31, and oxide layers 32 and 33 arranged above and below the oxide superconductor crystal layer 31, respectively.
With. The oxide superconductor crystal layer 31 is composed of several layers of oxide superconductor crystals and has a thickness of about 2 nm.
The oxide layers 32 and 33 are made of oxide crystal layers having a crystal structure similar to that of the oxide superconductor forming the oxide superconductor crystal layer 31, and each has a thickness of about 5 nm.

A superconducting multilayer wiring having the superconducting shield layer of the present invention having the structure shown in FIG. 1 (a) was produced. First, Mg
On the O (100) substrate 5, Y ₁ Ba ₂ Cu ₃ O _7-X was deposited by the sputtering method to form the ground plane 4.
Next, an MgO film was formed on the ground plane 4 by the CVD method to form the insulating layer 21. Y ₁ Ba ₂ Cu ₃ to be the first superconducting wiring 11 is formed on the insulating layer 21 by the off-axis sputtering method.
An O _7-X thin film was formed and processed into a wiring shape by reactive ion etching. The insulating layer 22 was again formed of MgO on the superconducting wire 11, and the superconducting shield layer 3 of the present invention was formed thereon.

The shield layer 3 of the present invention was manufactured as follows. First, the first oxide layer 32 is formed by the MBE method.
Then, a Pr ₁ Ba ₂ Cu ₃ O _7-y thin film to be formed was formed by the MBE method. The main film forming conditions are shown below. Substrate temperature 730 ℃ Pressure 5 × 10 ^-5 Torr Film thickness about 5nm (4 unit lattice)

Next, the Pr evaporation source is switched to the Y evaporation source, and Y ₁ Ba ₂ Cu ₃ O _{7-X is formed,} which becomes the oxide superconductor crystal layer 31 continuously on the oxide layer 32 formed as described above. The thin film was formed by the MBE method. Substrate temperature 700 ℃ Pressure 5 × 10 ^-5 Torr Thickness about 2nm (2 unit lattice)

Then, the Y evaporation source is switched to the Pr evaporation source, and a second oxide layer is continuously formed on the oxide superconductor crystal layer 31.
A Pr ₁ Ba ₂ Cu ₃ O _7-y thin film to be 33 was formed by the MBE method. The main film forming conditions are shown below. Substrate temperature 730 ℃ Pressure 5 × 10 ^-5 Torr Film thickness about 5nm (4 unit lattice)

Thus, the superconducting shield layer 3 of the present invention
Then, the insulating layer 23 was formed of MgO, and the Y ₁ Ba ₂ Cu ₃ O _7-X superconducting thin film to be the superconducting wiring 12 was also formed thereon by the off-axis sputtering method. The film forming conditions were the same as the conditions under which the first superconducting wiring 11 was formed.

Finally, the superconducting wiring 12 and the connection hole 6 are formed by reactive ion etching, and then the superconducting wiring 12 is formed.
An a-axis oriented oxide superconducting thin film for connecting 11 and 12 to each other is formed in the connection hole 6. As described above, the superconducting multilayer wiring including the superconducting shield layer 3 of the present invention is completed. The superconducting multilayer wiring produced as described above is in a superconducting state at 85 K, a superconducting current flows in the superconducting wirings 11 and 12, and due to the Meissner effect of the oxide superconducting crystal layer 31, electromagnetic waves are generated between them. It was confirmed to be shielded. When a short circuit occurs due to the connecting hole 6 through the superconducting shield layer 3, it is necessary to divide the superconducting shield layer 3 by focused ion beam processing after forming the superconducting shield layer 3.

[0020]

As described above, according to the present invention,
An extremely thin and highly effective superconducting shield layer is provided. When the superconducting shield layer of the present invention is used, for example, in a superconducting multilayer wiring of a superconducting integrated circuit, it becomes possible to narrow the wiring interval as compared with the conventional case. Further, even if a high-output signal current is passed through a certain superconducting wire, it will not interfere with the signals of other wires. The present invention further facilitates the application of superconducting technology to electronic devices.

[Brief description of drawings]

1A is a cross-sectional view of a superconducting multilayer wiring provided with a superconducting shield layer of the present invention, and FIG. 1B is a superconducting shield of the present invention used in the superconducting multilayer wiring of FIG. 1A. It is an expanded sectional view of a layer.

[Explanation of symbols]

 5 Substrate 11, 12 Superconducting wiring 31 Oxide superconductor crystal layer 32, 33 Oxide layer

Claims (1)

[Claims] 1. A number of unit lattices that are arranged between a pair of superconducting wires and extend parallel to at least one of the pair of superconducting wires in an insulating layer that electrically insulates the superconducting wires. An oxide superconductor crystal layer having a thickness, and an oxide layer having a crystal structure similar to the oxide superconductor arranged on both sides of the oxide superconductor crystal layer in contact with the oxide superconductor crystal layer A superconducting shield layer comprising: