JPH0719920B2 - Magnetic field coupling type Josephson integrated circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In a Josephson integrated circuit, when a magnetic field coupling type Josephson element is sandwiched between two ground planes when a magnetic shield is provided by a superconductor ground plane to form a multilayer structure. , The magnetic field sensitivity of the control line is reduced. As a countermeasure against this, a structure is proposed in which two magnetic field coupling type Josephson elements, for example, quantum interference type Josephson element magnetic field coupling inductance loops are provided in parallel and a control line is arranged between them.

[Industrial application field]

The present invention relates to a magnetic field coupling type Josephson integrated circuit having a structure in which the magnetic field sensitivity of a control line is prevented from deteriorating in a multi-layer structure.

Research has been conducted on a three-dimensional integrated circuit in which a magnetic field coupling type Josephson element is integrated in a logic circuit using a Josephson element, a memory circuit, and other digital and analog circuits, and further a multilayer structure is adopted.

[Conventional technology]

When integrating the Josephson device in a multilayer structure, in order to avoid magnetic field leakage and increase in wiring inductance,
The ground plane becomes more important than the single layer case.

In the case of the multi-layer structure, the Josephson element is sandwiched between the ground planes, so that the magnetic field sensitivity is lowered, and it is necessary to take measures to avoid this.

4 (1) to (3) are a perspective view, an equivalent circuit diagram and a sectional view of a conventional magnetic field coupling type Josephson integrated circuit, respectively.

The figure shows a two-junction quantum interference type Josephson device as an example of the magnetic field coupling type Josephson device.

In the figure, the base electrode 3 forms Josephson junctions 5 and 5A between the base electrode 3 and the counter electrode 4, and is used as an inductance loop for magnetic field coupling. The base electrode 3-Josephson junction 5-counter electrode 4-Josephson junction 5A-constituting the base electrode 3 and the lube.

The control line 6 is arranged close to the inductance loop 3.

The base electrode 3 and the counter electrode 4 are made of a superconductor such as niobium (N
b) and the Josephson junction 5 is formed of a thin alumina film.

Also, an insulating layer 8 for insulating the layers of the respective superconductor layers,
9 and 10 are formed by sputtering silicon dioxide (SiO ₂ ) or depositing silicon monoxide (SiO).

Up to now, almost no attempt has been made to make a multi-layer structure. Therefore, conventionally, the second ground plane 2 shown in FIG. 4 (3) was not used, but only the lower first ground plane 1 was used. .

However, when the second ground plane 2 is provided for multi-layering, the control line 6 is provided as will be described later in the section of action.
Since the current flowing in the loop flows approximately half in both directions, the image current flowing in the loop is also halved, and the magnetic field sensitivity is reduced to approximately half.

[Problems to be solved by the invention]

If the ground planes are formed above and below the magnetic field coupling type Josephson element for multi-layering, the magnetic field sensitivity is lowered.

[Means for solving problems]

To solve the above-mentioned problem, a first superconducting loop having a Josephson junction, a control line for generating a magnetic field, and the Josephson junction are provided via an insulating layer between ground planes made of two superconductors. A magnetic field coupling type having a Josephson element of a magnetic field coupling type which is arranged via an insulating layer so that a second superconducting loop shared in common and connected in parallel with a second superconducting loop are sequentially overlapped. Achieved by Josephson integrated circuits.

When the magnetic field / magnetic field coupling type Josephson element is formed in a multi-layered structure, the present invention is particularly necessary because the Josephson element is sandwiched between two ground planes.

[Action]

According to the present invention, when the ground planes are provided above and below, the image current flowing through the control line is divided into two parts up and down. Therefore, an inductance loop is also provided in parallel on the upper side of the control line so as to avoid a decrease in magnetic field sensitivity. is there.

FIGS. 3A to 3C are sectional views of an integrated circuit for explaining the concept of the present invention.

In the figure, (1) shows a conventional example having a ground plane on only one side, (2) shows a conventional example having a ground plane on both sides, and (3) shows the present invention having a ground plane on both sides.

The + and-in the circles shown in the figure are symbols that indicate the normal current direction, the + is behind the paper surface, and-is the direction in front of the paper surface.

Also, the part surrounded by the dotted line is the loop part of the quantum interference device, and the magnetic field created here poses a problem.

Assuming that the line width of the loop is W and the current flowing through the control line is I, the magnetic field H becomes (H) = I / W because the image current flows only in the lower side of the loop in (1).

In (2), the image current flows in two parts above and below the loop, so H = I / 2W.

In (3), since the loops are above and below, both are added up, and H = I / W., Which is the same as (1).

〔Example〕

1 (1) to (3) are a perspective view, an equivalent circuit diagram and a cross-sectional view of a magnetic field coupling type Josephson integrated circuit of the present invention, respectively.

The figure shows a two-junction quantum interference type Josephson device as an example of the magnetic field coupling type Josephson device in comparison with the conventional example.

In the present invention, the second inductance loop 7 is connected in parallel to the inductance loop 3 of the conventional example. Control line 6 with two inductance loops
To share.

Incidentally, 10 is an added insulating layer.

Although the number of control lines is one in the embodiment, it is of course possible to use a large number of lines.

Further, although the two-junction quantum interference device is used in the embodiment, instead of this, a one-junction quantum interference device, a three-junction quantum interference device,
... and so on.

FIG. 2 is a sectional view of an integrated circuit having a structure in which Josephson devices of the present invention are multilayered.

In the figure, the elements 24, 25 and 26, 27 of the present invention are formed between the ground planes 21, 22, 23, respectively.

〔The invention's effect〕

As described in detail above, according to the present invention, when the magnetic field coupling type Josephson element is formed in multiple layers, the magnetic field sensitivity can be kept the same as that in the case of one layer.

Therefore, a highly integrated and high-performance Josephson integrated circuit can be realized.

[Brief description of drawings]

1 (1) to (3) are perspective views, equivalent circuit diagrams and sectional views of the magnetic field coupling type Josephson integrated circuit of the present invention, and FIG. 2 has a structure in which the Josephson element of the present invention is multilayered. Sectional views of integrated circuits, FIGS. 3A to 3C are sectional views of integrated circuits for explaining the concept of the present invention, and FIGS. 4A to 4C are conventional magnetic field coupling type Josephson integrated circuits. It is a perspective view, an equivalent circuit diagram, and a sectional view of a circuit. In the figure, 1 is a first ground plane, 2 is a second ground plane, 3 is a base electrode (first inductance loop),
Reference numeral 4 is a counter electrode, 5 and 5A are Josephson junctions, 6 is a control line, 7 is a second inductance loop, and 8 to 10 are insulating layers.

Claims (2)

[Claims] 1. A first superconducting loop having a Josephson junction, a control line for generating a magnetic field, and the Josephson junction shared by an insulating layer interposed between ground planes made of two superconductors. And a magnetic field coupling type Josephson element arranged with an insulating layer so that the second superconducting loop connected in parallel with the first superconducting loop is sequentially overlapped with each other. Magnetic field coupling type Josephson integrated circuit. 2. The magnetic field coupling type Josephson integrated circuit according to claim 1, wherein the magnetic field coupling type Josephson element is formed in a multilayer structure.