JPH01280374A - Semiconductor substrate having superconductor layer - Google Patents

Abstract

PURPOSE:To obtain a semiconductor substrate having, on a semiconductor single-crystal substrate, a composite oxide superconductor thin-film layer whose superconducting characteristics including a critical temperature are excellent by a method wherein the thin-film layer composed of a composite oxide superconductor is formed on a substrate provided with a buffer layer composed of ZrO2 or MgO formed on a CdTe single crystal. CONSTITUTION:A thin-film layer composed of a composite oxide superconductor is formed on a substrate provided with a buffer layer composed of ZrO2 or MgO formed on a CdTe single crystal. It is desirable that the ZrO2 buffer layer or the MgO buffer layer is formed on a (100) plane of the CdTe single-crystal substrate. In addition, it is desirable that the ZrO2 or MgO buffer layer is formed by using a method of sputtering, ion plating, molecular beam epitaxy, CVD or the like; it is desirable that its film thickness is 50 to 1000Angstrom . In addition, it is desirable that also the composite oxide superconductor layer is formed by using the method of sputtering, ion plating, molecular beam epitaxy, CVD or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to semiconductor substrates. More specifically, the present invention relates to a semiconductor single crystal substrate having at least one superconductor layer.

The semiconductor substrate of the present invention not only uses the superconductor layer as a line material for a semiconductor integrated circuit, but also a Josephson element in which a Josephson bond is formed in the superconductor, a superconducting transistor in which a superconductor and a semiconductor are combined, and a hot electron It can be used as a material for elements such as transistors.

Conventional technology Conventional semiconductor integrated circuits are fabricated by forming an insulating film on a semiconductor single crystal substrate such as silicon, subjecting it to buttering, doping with impurities by thermal diffusion, ion implantation, etc. to fabricate the necessary elements, is deposited and wired.

Since the metal wiring pattern is formed by vapor deposition, its cross-sectional area is extremely small, resulting in loss of signal current.

Furthermore, although integrated circuit elements such as superconducting transistors and hot electron transistors that combine superconductors and semiconductors have been conceptually proposed, none have been manufactured using composite oxide superconducting materials specifically.

Problems to be Solved by the Invention The metal wiring patterns of semiconductor integrated circuits are formed by vapor deposition or the like, so their cross-sectional area is minute, and loss of signal current is unavoidable. Furthermore, in order to improve the operating speed of a semiconductor integrated circuit, it is important to improve the operating speed of the element itself, but it is also necessary to improve the signal propagation speed in wiring.

However, in conventional semiconductor integrated circuits, there is a limit to improving the signal propagation speed due to loss in the wiring portion. Furthermore, as the degree of integration of elements increases due to loss in wiring portions and density increases, power consumption increases, and the heat generated thereby naturally limits the degree of integration.

Furthermore, when forming elements such as superconducting transistors, hot electron transistors, and FETs that combine superconductors and semiconductors, a substrate with a uniform layer of superconducting material formed on a semiconductor single crystal substrate is essential. Among the Nb-based superconducting materials, there has been no one in which a layer of superconducting material is uniformly formed on a semiconductor substrate. Furthermore, metal-based superconductors have low critical temperatures and are not practical.

An object of the present invention is to solve the above problems and provide a semiconductor substrate having a composite oxide superconductor thin film layer having excellent superconducting properties including critical temperature on a semiconductor single crystal substrate.

Means for Solving the Problems According to the present invention, Z formed on a CdTe single crystal
Provided is a semiconductor substrate having a superconductor layer, characterized in that a thin film layer made of a composite oxide superconductor is formed on a substrate provided with a buffer layer made of r0z or MgO.

In the present invention, the above ZrO□ or! The thickness of the 4g○ buffer layer is preferably 50 to 1000A. Further, the crystal structure of the ZrO2 or MgO buffer layer is preferably one of the following.

1. The ZrO□ or MgO buffer layer has an amorphous structure.

2. The ZrO□ buffer layer is tetragonal and (100)
It has an orientation in which the plane is the surface, or it is a single crystal in which the (100) plane is the surface.

3.2rO□ buffer layer is cubic crystal, (100)
It has an orientation in which the plane is the surface, or it is a single crystal in which the (100) plane is the surface.

The 414g0h buffer layer has an orientation with the (100) plane as the surface, or is a single crystal with the (100) plane as the surface.

5. The MgO2 buffer layer has an orientation with the (111) plane as the surface, or is a single crystal with the (111) plane as the surface.

According to the invention, the superconductor is preferably formed of a composite oxide superconducting material.

Any known material can be used as this composite oxide superconducting material. For example, the substitution αl−Xβx)ryO− (where α is an element included in Group IIa of the periodic table,
β is an element included in group 11Ja of the periodic table, r is at least one element selected from groups Ib, IIb, llIb, rVa and ■a of the periodic table, and x, y, and z are each 0.1 ≦X≦0.9.0.4
≦y≦3.0.1≦Z≦5) Composite oxides that are considered to be mainly composed of perovskite-type or pseudo-perovskite-type oxides are preferred.

Examples of the Group Ia element α of the periodic table include Ba and Sr.

Ca5Mg5Be etc. are preferable, for example, Ba, Sr
can be mentioned, and 10 to 80% of this element α is Mg
, Ca.

It can also be replaced with one or two elements selected from Sr. In addition, the periodic table I
, T+n.

Lanthanide elements such as Yb and lu are preferred, for example Y
lLa, Ho, and among this element β,
It is also possible to substitute 10 to 80% with one or two elements selected from Sc or lanthanide elements.

The element T is generally Cu, but a part of it can be replaced with other elements selected from groups Ib, nb, llIb, rva and a of the periodic table, such as Ti, V, etc. Specifically, Y+Ba2Cu30t-x, La lBa2C
IJ 30=-X%La, 5r2Cu30t-x, H
o+Ba2Cu30t-X%Nd1Ba2Cu30q-
X, S+n, Ba, Cu3o7-x.

Snake u+Ba2cU307-xs Gd, BazCu,
,07-X5DV+Ba2CU:+Ch-x, Br
+Ba2Cu3off-X, Yb, BazCu, 0
A composite oxide superconductor represented by 7-X (where X is a number satisfying Q<x<l) is preferable.

Moreover, in the present invention, the formula: D t (E + -n, Can) s+
cLIh Op+* (where, DttBi or T1, E is Sr when D is Bi, Ba is when D is TI, l=4, and m satisfies 6≦m≦10. , n satisfies 4≦n≦8, and p = (31+2m
+21) / 2, # satisfies O<#<1,
* represents a number that satisfies -2≦*≦2) B+4Sr4Ca4CugO□o+* (however, * represents a number that satisfies -2≦*≦+2) ei2Sr2Ca2Cu30+o+* (however, * represents a number that satisfies -2≦) TI4Ba4Ca4CUsO□o+* (However, * represents a number that satisfies -2≦*≦+2) or T12Ba2Ca2Cu30+o+* (However, * represents a number that satisfies -2≦*≦+2) etc. Although it is preferable to use a superconductor that is considered to be a mixed phase mainly consisting of the complex oxides shown, a single phase of any of the above complex oxides may be used.

The above ZrO2 or MgO buffer layer is made of the above CdTe.
Advantageously, it is formed on the (100) plane of the substrate.

Function The main feature of the semiconductor substrate having a superconductor layer of the present invention is that a composite oxide superconductor layer is formed on a semiconductor single crystal substrate via an 8771 layer made of ZrCh or MgO. That is, unlike conventional ones, the semiconductor substrate having a superconductor layer of the present invention is not only a combination of a semiconductor and a composite oxide superconductor;
It includes a buffer layer that improves the interface state between the semiconductor and the composite oxide superconductor.

A conventional semiconductor substrate having a superconductor layer is simply a composite oxide superconductor thin film formed on a semiconductor substrate. Therefore, the interface state between the semiconductor and the composite oxide superconductor is unstable, and most devices do not function as a semiconductor device or have poor characteristics.

In the present invention, ZrO or M
By providing a buffer layer made of gO and further forming a composite oxide superconductor thin film on top of it, the interface condition has been significantly improved compared to conventional ones, and the characteristics as a semiconductor device have also been improved. .

In the present invention, ZrO forms the buffer layer.

Alternatively, the crystal structure of MgO is preferably one of the following.

1.2rO□ or MgO buffer layer has an amorphous structure.

2. The ZrO2 buffer layer is tetragonal and (100)
It has an orientation in which the plane is the surface, or it is a single crystal in which the (100) plane is the surface.

3.2rO□ buffer layer is cubic crystal, (100)
It has an orientation in which the plane is the surface, or it is a single crystal in which the (100) plane is the surface.

4. The MgCh buffer layer has an orientation with the (100) plane as the surface, or is a single crystal with the (100) plane as the surface.

5. The Mg○2 buffer layer has an orientation with the (111) plane as the surface, or is a single crystal with the (111) plane as the surface.

This is to improve the crystallinity of the composite oxide superconductor, and the composite oxide superconductor thin film formed on the buffer layer with the above crystal structure has a C-axis 2 of the crystal parallel to the substrate deposition surface. Since the crystals have orientation properties that are aligned at close angles, the critical current density Jc in a specific surface direction and depth direction is improved.

The semiconductor substrate having the superconductor layer of the present invention can not only be used as a semiconductor single crystal substrate in which the wiring portion is replaced with a composite oxide superconductor from a conventional metal, but also a Josephson junction can be formed in the composite oxide superconductor portion. It can also be used as a device material for forming semiconductor devices or new semiconductor elements such as superconducting transistors and thermionic transistors in which a semiconductor substrate and a superconductor are combined.

The composite oxide superconductor used in the semiconductor substrate having a superconductor layer of the present invention is Y1B, also called YBCO.
A composite oxide superconductor with a multilayer perovskite crystal structure represented by a2Cua 0t-x, B14Sr4Ca4[:uBc12o+* (However, *
represents a number satisfying -2≦*≦+2) or T14Ba4C
A complex oxide superconductor represented by a4Cu602o-* (where * represents a number satisfying -2≦*≦+2) is preferable. However, the superconductor used in the present invention is not limited to these, and any known superconductor can be used.

In addition, sputtering, ion blasting, molecular beam epitaxy, CVD (chemical vapor phase reaction), etc. can be used to form a ZrO2 or MgO buffer layer to improve the interface between the semiconductor single crystal substrate and the composite oxide superconductor. It is preferable to use a method such as method), and the film thickness is required to be 50 Å or more in order to improve the interface condition.
Further, in order to cause a superconducting proximity effect between the semiconductor and the insulator, the thickness is preferably 1000 Å or less.

Furthermore, in order to produce a semiconductor substrate having a superconductor layer of the present invention, sputtering, ion blating, molecular beam epitaxy, CVD (
It is preferable to form the composite oxide H conductor layer by a vapor deposition method such as a chemical vapor phase reaction method or a method similar to a vapor deposition method.

At that time, it is preferable to form the composite oxide superconductor layer at a substrate temperature of 700° C. or lower so as not to impair the physical properties of the semiconductor single crystal.

Further, it is preferable that the 1rO2 buffer layer or the MgO buffer layer described above be formed on the (100) plane of the CdTe single crystal substrate. This is because the buffer layer can easily adopt the crystal structure described above, and the buffer layer formed on the above-mentioned surface of the CdTe single-crystal substrate can easily adopt the crystal structure preferable in the present invention described above, and the state of the interface It is also advantageous for improving the

EXAMPLES Hereinafter, the present invention will be specifically explained by examples, but the following are merely examples of the present invention, and it goes without saying that the scope of the present invention is not limited in any way by the following disclosure. be.

ZrO2 was deposited as a buffer layer on a CdTe single crystal substrate.
A composite oxide superconductor layer was formed on the buffer layer to produce a semiconductor substrate having a superconductor layer of the present invention. The ZrO□ buffer layer was formed using a sputtering method at a temperature of 400° C. on a CdTe single crystal substrate.

Commercially available 81203 powder, 5rCOs powder, CaCO3 powder, CuO powder, Bi, Sr, Ca, Cu atomic ratio Bi:Sr:Ca:Cu 1.4:1
: 1 : 1.5 Bi-3r-Ca-Cu-0 composite oxide made by sintering raw material powder according to a conventional method,
YBa2Cu, sOx sintered powder and lo[3
(10
0) Form a composite oxide superconductor layer on the surface. Paying particular attention to the positional relationship between the substrate and target and the magnitude of high-frequency power, sputtering is performed at a substrate temperature of 700° C. to grow a composite oxide superconductor layer to a thickness of 1000° C. and use it as a sample. For comparison, CdTe without forming a buffer layer
A composite oxide superconductor layer was formed on the (100) plane of a semiconductor single crystal substrate under exactly the same conditions.

All of the above semiconductor substrates having a superconductor layer of the present invention have good interface conditions between the semiconductor and the buffer layer, and between the buffer layer and the superconductor layer, and have excellent properties as semiconductor device materials.

Further, the superconducting critical temperature and critical current at 77K of the superconducting layer of each sample are shown below.

As explained above, the semiconductor substrate having the superconductor layer of the present invention is very effective as a substrate for semiconductor devices.

Effects of the Invention The present invention provides a semiconductor substrate having a superconductor layer that is very effective as a novel semiconductor device material.

The present invention further promotes higher speed and higher density of semiconductor devices. Further, unlike Josephson devices, the present invention can be applied to semiconductor devices using superconductors having three or more terminals.

Patent applicant: Sumitomo Electric Industries, Ltd.

Claims (1)

[Claims] A semiconductor substrate having a superconductor layer, characterized in that a thin film layer made of a composite oxide superconductor is formed on a substrate provided with a buffer layer made of ZrO_2 or MgO formed on a CdTe single crystal.