JPH02389A - Semiconductor substrate with superconductor layer - Google Patents

Abstract

PURPOSE:To bring a wiring for an IC to a superconductive state, and to reduce the loss of currents while enabling operation at high speed by forming a composite oxide superconductive layer shaped onto an oxide substrate and an Si single crystal layer formed onto the superconductive layer. CONSTITUTION:A semiconductor substrate is formed of a composite oxide superconductive layer shaped onto an oxide substrate and an Si single crystal layer formed onto the superconductive layer. An integrated circuit using a composite oxide group superconductive material as a wiring material is shaped by machining the semiconductor substrate. An integrated circuit substrate for forming a novel superconducting element such as 21 semiconductor device, in which a Josephson junction is shaped to a composite oxide superconductor section, a superconducting transistor, in which the semiconductor substrate and the superconductor are combined, and a hot electron transistor is acquired. Accordingly, wirings for an IC are brought to a superconductive state, and the loss of currents can be reduced while high-frequency transmission or high speed operation can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to semiconductor substrates. More specifically, S formed on an oxide substrate via a composite oxide superconductor layer
The present invention relates to the structure of a novel semiconductor substrate that includes an i-layer and can be used not only as a material for semiconductor circuits but also as a material for superconductor devices such as Josephson devices, superconducting transistors, and hot electron transistors.

BACKGROUND OF THE INVENTION The electrical conduction phenomenon, which is said to be a phase transition of electrons, is a phenomenon in which the electrical resistance of a conductor becomes zero under certain conditions and exhibits complete diamagnetic property. That is, under superconductivity, there is no power loss at all even when current is passed through a superconductor, and a high-density current continues to flow forever. Therefore, for example, if superconductivity is applied to power transmission technology, the approximately 7%
This can significantly reduce unavoidable power transmission losses. In addition, in the field of power generation technology, MH
Along with D power generation and electric motors, it is expected to be a technology that advantageously promotes the realization of nuclear fusion reactions, which are said to consume more power than the power generator to start up.

It is also expected to be used as a power source for magnetic levitation trains, electromagnetic propulsion ships, etc., and also for use in NMR 1π meson therapy, high-energy physics experiment equipment, etc. in the measurement and medical fields.

Furthermore, apart from the use in large-scale equipment as mentioned above,
Applications of superconducting materials to various electronic devices have also been proposed. A typical example is an element that utilizes the Josephson effect, in which quantum effects appear macroscopically due to applied current when superconducting materials are weakly bonded together. Tunnel junction type Josephson devices are expected to be extremely high-speed switching devices with low power consumption because the energy gap of superconducting materials is small. Furthermore, since the Josephson effect on electromagnetic waves and magnetic fields appears as a precise quantum phenomenon, it is expected that Josephson elements will be used as ultra-sensitive sensors for magnetic fields, microwaves, radiation, etc. Furthermore, as the degree of integration of electronic circuits increases, it is expected that power consumption per unit area will reach the limit of cooling capacity. Therefore, there is a need for the development of superconducting elements for ultra-high-speed computers.

Conventionally, despite various efforts, the superconducting critical temperature Tc of superconducting materials could not exceed 23K for Nb and Ge for a long period of time. On the other hand, in 1986, Bednautz and Mueller et al. discovered that complex oxide superconducting materials have a high Tc, greatly opening up the possibility of high-temperature superconductivity (Be
dnorz, Mtller, “Z, Phys.

864, 1986.189”).

It has been known for some time that composite oxide ceramic materials exhibit superconducting properties.

For example, in U.S. Pat. No. 3.932.315, Ba
It has been described that -Pb-Bi-based composite oxides exhibit superconducting properties, and also in JP-A-60-173.
Publication No. 885 describes that a Ba-B1-based composite oxide exhibits superconducting properties. However, the T of the complex oxide superconducting materials known so far. is 10
In order to obtain the superconducting phenomenon, the use of expensive and rare liquid helium (boiling point 4.2 K) was unavoidable.

The oxide superconductor discovered by Bednautz and Mueller et al. has a composition of (La, Ba) 2cu 04 and is thought to have a K2NiF type crystal structure. This composite oxide-based superconducting material has a crystal structure similar to that of previously known perovskite-type oxide-based superconducting materials, but its To value is approximately 30, which is significantly higher than that of conventional superconducting materials. Met.

Furthermore, in February 1987, Chu et al. discovered a Ha-Y-Cu-based composite oxide that exhibits a critical temperature of 90 degrees. This complex oxide commonly known as YBCO is Y + B
It is thought to have a composition represented by a2Cuz Ch-x.

Furthermore, the subsequently discovered Bi-5r-Ca-Cu-based and TI-Ba-(, a-Cu-based composite oxides were
Not only does it have a Tc of 100 or more, but it is also chemically stable, and its superconducting properties do not deteriorate over time as much as YBCO and the like, so it is expected to be suitable for practical use.

The discovery of these new composite oxide-based superconducting materials has recently increased the momentum for realizing high-temperature superconductors.

Problems to be Solved by the Invention Incidentally, semiconductor integrated circuits widely used in today's electronic technology field generally form an insulating film on a semiconductor single crystal substrate such as silicon, and then heat diffusion and ionization according to a predetermined pattern. A desired element or circuit is formed by performing doping such as implantation. The wiring patterns in such circuits are formed by vapor-depositing metal materials, but their cross-sectional areas are extremely small, resulting in extremely large signal current losses. Furthermore, since current loss is dissipated as heat, there is a limit to the degree of integration or operating speed using conventional techniques.

Therefore, in the field of integrated circuits, by making wiring superconducting, it becomes possible to overcome the limits of the characteristics of these integrated circuits.

In addition, various devices have been proposed that combine superconductors and semiconductors, such as transistors that combine superconductors and semiconductors, hot electron transistors, and devices that utilize superconductivity phenomena such as Josephson devices. Currently, there are no known members that can be used to make this.

Therefore, an object of the present invention is to provide a novel semiconductor substrate including a superconducting layer that can be used for producing superconducting wiring or superconducting elements.

Means for Solving the Problems According to the present invention, an oxide substrate, an oxide superconducting layer formed on the substrate, and a Si single crystal layer formed on the oxide superconducting material layer are provided. A semiconductor substrate is provided.

The main feature of the semiconductor substrate according to the present invention is that it includes a composite oxide superconductor layer formed on an oxide substrate and a Si layer formed on this composite oxide superconducting material layer. These characteristics make it a basic material for new semiconductor devices that utilize superconductivity phenomena.

It is also preferable to form a buffer layer on the superconducting thin film before laminating the Si single crystal layer.

This buffer layer has the function of preventing atoms and molecules constituting the semiconductor from diffusing into the superconductor thin film and facilitating the formation of a semiconductor single crystal layer. Therefore, it is preferable that the lattice constant is close to that of the semiconductor single crystals to be laminated. For example, PT is preferable as the buffer layer.

That is, by processing the semiconductor substrate according to the present invention, it is not only possible to fabricate an S1 integrated circuit using a composite oxide superconducting material as a wiring material, but also to form a Josephson junction in the composite oxide superconductor portion. It can be used as an integrated circuit substrate or device substrate for forming a semiconductor device or a new superconducting element such as a superconducting transistor or hot electron transistor that combines a semiconductor substrate and a superconductor.

The superconducting material forming the superconducting material layer in the semiconductor substrate according to the present invention may be Y-Ba-Cu based or T
Composite oxide-based superconducting materials having an oxygen-deficient perovskite crystal structure represented by the l-Ba-Ca-Cu system can be advantageously used, but are not limited thereto, and any known superconductor may be used. It is possible to select and use.

In addition, since these composite oxide-based superconducting materials generally exhibit excellent superconducting properties only in a specific crystal structure, it is preferable to use an oxide-based substrate as the substrate when producing them.

That is, to explain the above-mentioned Y-Ba = Cu-based oxide superconducting material as an example, in this composite oxide-based superconducting material, current tends to flow in a direction parallel to the plane determined by the a-axis and b-axis of the crystal. . MgO single crystal substrate or 5rT
When the (001) plane of the i03 single crystal substrate is used as the film formation surface, the composite oxide superconductor thin film formed on the film formation surface has a crystal C axis that is perpendicular or perpendicular to the substrate film formation surface. Since the angles are close to each other, the critical current density Jc becomes particularly large. Therefore, it is preferable to use the (001) plane of the MgO single crystal substrate or the SrTiO3 single crystal substrate as the film forming surface. Furthermore, by using a (110) substrate and making the C axis parallel to the substrate, it is possible to obtain a high current density also in the depth direction of the film. Furthermore, MgO and 5rTiO,
Since the coefficient of thermal expansion is close to that of the above composite oxide superconductor, unnecessary stress is not applied to the thin film during the heating-cooling process, and there is no risk of damaging the thin film.

Furthermore, substrate materials that can be used for the semiconductor substrate according to the present invention include MgO single crystal substrate, 5rTiO+ single crystal substrate,
Al2O3 single crystal substrate, NbO3 single crystal substrate, Li
Preferred examples include a TaO3 single crystal substrate or a ZrO2 single crystal substrate.

Further, the material forming the superconducting material layer in the semiconductor substrate of the present invention has the general formula: (α, -UβX)γ,02 (where α is an element included in group a of the periodic table, and β
is an element included in group ■, a of the periodic table, and T is an element selected from group Ib, IIb, mb, I'Va, and group ■ of the periodic table (both are one element, are 0.1≦X≦0.9.0.4≦y≦3.0.1≦2≦, respectively.
Examples include those having a composition represented by the formula (a number satisfying 5) and mainly consisting of perovskite or pseudo-perovskite oxides.

Here, the periodic table [group a elements α include Ba,
Specific examples include Sr, Ca, Mg, Be, etc., and particularly preferable elements include Ba, Sr, etc.
Furthermore, 10 to 80% of the element α is M
It can also be replaced with one or two elements selected from g1Ca and Sr.

In addition to Y, the above element β includes La5Sc, Ce, and G.
d.

Specific examples include Ho, Er, Tm, Yb, Lu, etc., and particularly preferable ones include Y, La, Ho, etc., and furthermore, among the elements β, 10 to 80
% can also be replaced with one or two elements selected from Sc or lanthanide elements.

Element T is generally Cu, but may also include AI, Fe, C
o, N1, Zn, Ag, Ti, etc. can also be used, and furthermore, some of them are listed in the periodic table Ib, [b, I] Ib,
IVa and other elements selected from group II, such as T
It can also be replaced with 1, ■, etc.

Other advantageous materials that can be applied to the superconducting material layer of the semiconductor substrate according to the present invention include the formula: α4(βl-111Cax)mCuhOp+y, where α is Bi or T1 and β is when α is Bi. is Sr, and when α is Tl, it is Ba, m satisfies 6≦m≦10, n satisfies 4≦n≦8, p=5+m+n, and X is 0.2<x<0. .8, and y represents a number satisfying -2≦y≦2).

In addition, in order to produce the semiconductor substrate according to the present invention, it is preferable to use the following procedure. Sputtering, vacuum evaporation, molecular beam epitaxy,
Physical vapor deposition method such as ion beam evaporation or CVD method such as thermal CVD method, plasma CVD method, optical CVD method, MoCVD method, etc.
method to form a composite oxide superconductor thin film. As the physical vapor deposition method, magnetron sputtering is particularly preferred.

In addition, after the film is formed, post-treatment such as heat treatment in an oxygen atmosphere or exposure to oxygen plasma is performed to appropriately adjust the oxygen concentration in the composite oxide superconductor crystal that constitutes the above-mentioned thin film. is preferred.

After performing these treatments, a semiconductor single crystal layer is laminated on the superconducting thin film by a known method such as a CVD method or an MBE method.

Whichever method is used, care must be taken to maintain the atmosphere and substrate temperature so as not to impair the properties of the superconductor.

Furthermore, when producing a semiconductor element using a semiconductor substrate having a superconductor layer of the present invention, it is also preferable to form the semiconductor layer after processing the superconductor thin film into a required shape by etching or the like in advance. However, since the surface of the semiconductor substrate having the superconductor layer of the present invention is an 81 semiconductor, it is also possible to microfabricate it using conventionally known techniques.

Hereinafter, the present invention will be specifically explained with reference to examples, but what is described below 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.

A semiconductor single crystal layer of Example Si was formed on a composite oxide superconductor thin film to produce a semiconductor substrate having a superconductor layer of the present invention.

YBa2Cu4. s Ox sintered powder and HoBa
2.3Cu4.70x as target, MgO single crystal substrate and 5rTiO.

A composite oxide superconductor thin film was formed on each (100) plane of the single crystal substrate by a known magnetron sputtering method. Particular attention was paid to the positional relationship between the substrate and the target and the magnitude of the high-frequency power, and sputtering was performed at a substrate temperature of 700°C to grow a composite oxide superconductor layer of up to 1,000 layers.

After forming a superconducting thin film, temperature at 850°C in an oxygen atmosphere of 1 atm.
After heating for 1 hour, the temperature was lowered to 400℃ at a cooling rate of 3℃/min, and from 400℃ to room temperature at a cooling rate of 10℃/min.
Cooled at a cooling rate of 1 minute.

After that, S was deposited on each superconducting thin film using the C and VD methods.
i Form a semiconductor single crystal layer.

All of the semiconductor substrates having the superconductor layer of the present invention produced as described above had a good interface between the semiconductor and the superconductor, and had excellent properties as a semiconductor device material. Further, the superconducting critical temperature of the superconductor layer of each sample is shown in Table 1 below. Furthermore, in Table 1,
Tco indicates the temperature at which the electrical resistance of the sample begins to drop rapidly, and Tci indicates the temperature at which the electrical resistance can no longer be measured.

Table 1 frequency transmission or high-speed operation can be realized. Furthermore, since heat generation due to current loss is reduced, a higher degree of integration can be achieved.

Furthermore, it can be used to fabricate superconducting devices such as Josephson devices or hot electron transistors, and is extremely effective in the application of superconducting technology.

Patent applicant: Sumitomo Electric Industries, Ltd.

Claims (1)

[Claims] A semiconductor substrate comprising an oxide substrate, an oxide superconducting layer formed on the substrate, and a Si single crystal layer formed on the oxide superconducting material layer.