JPH04314370A - Superconducting multilayer device and its manufacturing method - Google Patents

Abstract

PURPOSE:To eliminate grain boundary which causes magnetic and electrical noises by using a single crystalline superconductive film when constituting a superconductive laminated element by laminating a superconductive layer and an insulating layer. CONSTITUTION:A single crystalline superconductive contact layer 13 and a single crystalline insulating layer 14 are laminated on a first single crystalline superconductive wiring 12, and a single crystalline superconductive wiring 15 is further arranged thereon. Therefore, grain boundary is eliminated inside a superconductive wiring and remaining magnetic field is reduced, thereby improving normal operativity and reliability of a superconductive laminated element.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a superconducting multilayer element formed by laminating a superconducting layer and an insulating layer, and a method for manufacturing the same.

0002

[Prior art] The conventional laminated structure of superconducting layer and insulating layer is
For example, iTriple E transaction on
It is described on page 102 of Magnetics Magazine, Volume 21, No. 2, March 1985 issue. That is, a stacked structure in which a polycrystalline insulating layer is stacked on a polycrystalline superconducting wiring layer has been used. In addition, in the manufacturing method, a crystallically discontinuous polycrystalline insulating layer is laminated on a polycrystalline superconducting wiring layer.

0003

[Problem to be solved by the invention] Grain boundaries exist in conventional superconducting wiring layers, and even after the inside of the crystal grains becomes a superconducting layer at a temperature below the critical temperature, normal conduction occurs at the grain boundaries. area remained. Therefore, even if the temperature of the superconducting wiring layer is lower than the critical temperature, magnetic flux is trapped in the grain boundary normal conduction region, weakening the effective Meissner effect of the superconducting wiring layer. The trapped magnetic flux becomes a source of magnetic noise in the superconducting circuit, and its thermal motion becomes a source of electrical noise, impairing the normal operation or reliability of the superconducting circuit.

[0004] An object of the present invention is to provide a superconducting multilayer device and a method for manufacturing the same, which eliminates the trapped magnetic flux of the superconducting wiring layer and reduces magnetic noise and electrical noise.

[0005]

[Means for Solving the Problems] The present invention provides a superconducting multilayer element configured by laminating a superconducting layer and an insulating layer. A contact layer and a single crystal insulating layer having the same thickness as the single crystal superconducting contact layer are arranged adjacent to each other; It is characterized in that a second single-crystal superconducting wiring layer is disposed overlying it.

[0006] The present invention also provides a method for manufacturing a superconducting multilayer element formed by laminating a superconducting layer and an insulating layer.
a step of forming a single crystal superconducting wiring layer, a step of thinning a part of the first single crystal superconducting wiring layer leaving a single crystal superconducting contact layer region, and a step of forming a thin first single crystal superconducting wiring layer; A step of epitaxially growing a single crystal insulating layer having the same thickness as the single crystal superconducting contact layer on the conductive wiring layer, and overlaying the single crystal superconducting contact layer and/or the single crystal insulating layer. , a step of epitaxially growing a second single-crystal superconducting wiring layer.

[0007]

[Operation] A superconducting polycrystalline film constitutes a macroscopic film in which single crystal grains of a certain size are irregularly gathered. In the boundary regions of adjacent single crystal grains, so-called grain boundaries, mutual crystallinity is discontinuous, and energy levels on the crystal surface and potentials due to crystal dislocations are disturbed, resulting in loss of superconductivity, or , exhibits only weak superconductivity compared to crystal grains. Therefore, when a superconducting polycrystalline film is placed in an environment below the critical temperature, even though the inside of the crystal grains becomes superconductive, the grain boundaries remain in a normal conductive state. Due to the Meissner effect, the magnetic field is removed from within the crystal grains, but the magnetic field remains at the grain boundaries. In order to avoid this so-called magnetic flux trapping phenomenon, it is effective to eliminate grain boundaries that are the center of magnetic flux trapping. In order to effectively reduce residual magnetic fields, which are one of the causes of magnetic or electrical noise, it is necessary to eliminate residual magnetic fields from all superconductors used in devices.

In the superconducting multilayer device of the present invention, a single crystal superconducting layer is used for the first superconducting wiring, and a superconducting layer is further used for the second superconducting wiring and connecting the first and second superconducting wirings. A single crystal film was also used for the conductive contact layer. As a result, the grain boundaries disappeared, and the magnetic flux trapped there, as well as the residual magnetic field caused by it, could be removed. As a result, magnetic noise and electrical noise are reduced, and the normal operation and reliability of superconducting circuits are improved.

[0009] In the method for manufacturing a superconducting multilayer device of the present invention,
A single crystal superconducting layer is formed as the first superconducting wiring, an insulating layer layered on top of it is made into a single crystal by epitaxial growth, and a second superconducting wiring layer layered thereon is made into a single crystal by epitaxial growth. did. As a result, the grain boundaries disappeared, and the trapped magnetic flux and residual magnetic field caused by them could be removed. As a result, magnetic noise and electrical noise are reduced, and the normal operation and reliability of the superconducting circuit are improved.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view for explaining an embodiment of a superconducting multilayer device according to the present invention. for example,

0011
]

[Math 1]

A niobium single crystal film having a thickness of, for example, 200 nm is disposed as a first single crystal superconducting wiring layer 12 using sapphire having a main surface as the substrate 11 . Overlaid on the first single crystal superconducting wiring layer to a thickness of, for example, 200 nm.
A niobium single crystal superconducting contact layer 13 and a sapphire single crystal insulating layer 14 having a thickness of, for example, 200 nm are arranged. Single crystal superconducting contact layer 13 and single crystal insulating layer 1
For example, the thickness is 200n.
A second single crystal superconducting wiring layer 15 using a niobium single crystal film of m is disposed.

The superconducting multilayer device of this embodiment may include a Josephson element, and may also include a resistor. Alternatively, a bulk niobium single crystal may be used for the substrate to form an element structure that serves both as the substrate and the first single-crystal superconducting wiring layer.

FIG. 2 is a cross-sectional view of a superconducting multilayer device manufacturing process for explaining an embodiment of the manufacturing method of the present invention.

First, as shown in FIG. 2(a), for example,

[
0016

[Math 2]

Using sapphire having the main surface as the substrate 21, a 400 nm thick niobium single crystal film was grown as the first single crystal superconducting wiring layer 22 by, for example, the molecular beam epitaxial method.

Next, as shown in FIG. 2(b), for example, C
The first single-crystal superconducting wiring layer 22 was etched to a depth of 200 nm, for example, by a reactive ion etching method using F4 gas, leaving a region of the single-crystal superconducting contact layer 23.

Next, as shown in FIG. 2(c), a sapphire single crystal film having a thickness of, for example, 200 nm was grown by, for example, molecular beam epitaxial method to form a single crystal insulating layer 24.

Next, as shown in FIG. 2(d), for example, polystyrene is applied, heated at 200° C. for 30 minutes to flatten the sample surface, and then etched back using, for example, reactive ion etching. Single crystal superconducting contact layer 23
exposed the surface.

Finally, as shown in FIG. 2E, a 200 nm thick niobium single crystal film is grown as a second single crystal superconducting wiring layer 25 by, for example, molecular beam epitaxial method. The shape was processed using the ion etching method.

[0022]

[Effects of the Invention] According to the superconducting multilayer device and its manufacturing method of the present invention, grain boundaries in superconducting wiring within the device are eliminated,
The trapped magnetic flux and residual magnetic field caused by grain boundaries are eliminated, making it possible to improve the normal operation and reliability of superconducting circuits.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a superconducting multilayer device according to the present invention.

FIG. 2 is a manufacturing process sectional view showing an embodiment of the manufacturing method of the present invention.

[Explanation of symbols]

11, 21 Substrate 12, 22 First single crystal superconducting wiring layer 13, 23
Single crystal superconducting contact layer 14, 24 Single crystal insulating layer

Claims (2)

[Claims] Claim 1: A superconducting multilayer element configured by laminating a superconducting layer and an insulating layer, in which a single crystal superconducting contact layer and a single crystal superconducting contact layer are superposed on a first single crystal superconducting wiring layer; A conductive contact layer and a single crystal insulating layer of the same thickness are arranged adjacent to each other, and a second A superconducting multilayer device characterized by having a single crystal superconducting wiring layer arranged therein. 2. A method for manufacturing a superconducting multilayer device formed by laminating a superconducting layer and an insulating layer, comprising the steps of forming a first single crystal superconducting wiring layer and forming a single crystal superconducting contact layer region. A step of thinning a part of the first single-crystal superconducting wiring layer while leaving a part of the first single-crystal superconducting wiring layer thin, and forming a single-crystal insulating layer with the same thickness as the single-crystal superconducting contact layer on the thinned first single-crystal superconducting wiring layer. and a step of epitaxially growing a second single-crystal superconducting wiring layer over both or either of the single-crystal superconducting contact layer and the single-crystal insulating layer. A method for manufacturing a superconducting multilayer device.