JPH01132178A - Superconducting transistor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a superconducting transistor capable of forming a multilayer structure and an arbitrary shape by a method wherein at least two facing superconducting electrodes, at least one control electrode used to control an electric current flowing between the superconducting electrodes and an insulating layer are formed on a semiconductor substrate so as to come into contact with it. CONSTITUTION:The following are provided: a semiconductor substrate 1; at least two facing superconducting electrodes 2 formed on the semiconductor substrate 1 so as to come into contact with it; at least one control electrode 3 which has been formed on the semiconductor substrate 1 so as to come into contact with it and which controls an electric current flowing between the superconducting electrodes 2; an insulating layer 4 which has been formed on the semiconductor substrate 1 so as to come into contact with it and which has been formed on one face where said superconducting electrodes 2 and said control electrode 3 have not been formed. For example, a superconducting transistor is constituted by forming the following: one pair of facing superconducting electrodes 2 partitioned by an insulating layer 4 formed perpendicularly to a semiconductor substrate 1 on the surface of the semiconductor substrate 1; one pair of control electrodes 3. When a voltage is impressed on the control electrodes 3, a superconducting weak coupling state between the superconducting electrodes 2 can be controlled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to superconducting devices, and particularly to a superconducting transistor in which the number of superconducting electrons tunneling through a semiconductor is controlled by a voltage applied to a control electrode, and a method for manufacturing the same. Regarding.

[Conventional technology]

Conventionally, as a superconducting element that combines a semiconductor and a superconductor, for example, Japanese Patent Laid-Open Nos. 122287-1987 and 1983-
There is one disclosed in No. 18776.

In the former superconducting element, as shown in FIG. 5, a pair of superconducting electrodes 2a are formed facing each other on a semiconductor substrate la with an insulating layer 4a interposed therebetween. It has a laminated structure in which a control electrode 3a is formed with a layer 4b interposed therebetween.

On the other hand, the latter superconducting element, as shown in FIG. It has a stepped structure in which the electrode 2C is connected by a weak linker 8.

(Problems to be Solved by the Invention) However, among the above conventional examples, using the superconducting element beam lithography technique and etching technique shown in FIG.
It is manufactured through many steps. For this reason, precision is required for mask positioning for lamination or etching, resulting in problems in controllability of device performance and yield. Further, in the superconducting element shown in FIG. 6, since the weak coupler portion is formed in 411 layers in the stepped portion, there are problems such as wire breakage.

An object of the present invention is to solve the above-mentioned problems, and further to provide a superconducting transistor that can have a multilayer structure and any shape, unlike conventional superconducting elements, and a method for manufacturing the same.

[Means for solving problems]

The present invention includes: a semiconductor substrate; at least two opposing superconducting electrodes provided on and in contact with the main semiconductor substrate; and at least one superconducting electrode provided on and in contact with the semiconductor substrate for controlling a current flowing between the superconducting electrodes. A superconducting transistor having one control electrode and an insulating layer provided on one surface in contact with the semiconductor substrate where the superconducting electrode and the control electrode are not provided, and an oxide superconductor on the semiconductor substrate. This method of manufacturing a superconducting transistor includes the step of forming an insulating layer by changing the phase or composition of the oxide superconducting thin film after forming the thin film.

FIG. 1 is a schematic top view showing an example of a superconducting transistor of the present invention, and FIG. 2 is a sectional view taken along line AB in FIG.

The superconducting transistor of the present invention has a pair of opposing superconducting electrodes 2 and a pair of control electrodes 3 separated by an insulating layer 4 provided perpendicularly to the semiconductor substrate 1 on the upper surface of the semiconductor substrate 1. are doing. Further, the superconducting electrode 2, the control electrode 3, and the insulating layer 4 have a flat structure formed on the same plane of the semiconductor substrate 1. It is characterized in that the superconducting weak coupling state between the superconducting electrodes 2 is controlled by the voltage applied to the control electrode 3. In addition, although the number of control electrodes 3 may be one, it is desirable to use a pair of control electrodes in order to stabilize the characteristics.

Next, a method for manufacturing a superconducting transistor according to the present invention will be explained. As shown in FIG. 3, the semiconductor substrate 1 has an oxide superconductor @
When the film 9 is deposited (Figs. 3 (1) and (2)), a part of it undergoes a phase change or a composition change to become an insulator, forming the oxide superconducting thin film 9 that serves as the superconducting electrode and the control electrode.
It is possible to form an insulating layer 4 that separates the
), (4)).

Note that the vapor deposition method may be a vacuum vapor deposition method, a sputtering method, an ion blating method, an electron beam vapor deposition method, etc., and is not particularly limited.

A phase change or a composition change can be caused, for example, by irradiation with an electron beam or an ion beam.

According to the above manufacturing method, multiple mask alignments and vapor deposition on stepped portions are not required, and the superconducting transistor of the present invention can be obtained through simple steps. Therefore, the yield is improved and problems such as wire breakage can be solved.

(Example) Hereinafter, the present invention will be explained based on Examples.

Example 1 FIG. 1 is a schematic top view showing an example of a superconducting transistor of the present invention. A superconducting electrode 2 and a control electrode 3 are formed separated from each other by an insulating layer 4 having a width of 50 mm. Since these superconducting electrodes 2, control electrodes 3, and insulating layer 4 are formed on the semiconductor substrate 1, there is a superconducting weak coupling state between the superconducting electrodes 2. This embodiment has a field effect transistor configuration in which this superconducting weakly coupled state can be controlled by a voltage applied to the control electrode 3. If the superconducting weak coupling state can be controlled, the superconducting current flowing between the superconducting electrodes 2 can be changed.

Next, a method for manufacturing this superconducting transistor will be explained with reference to FIG.

A film of Er-Ba-Cu-0 is formed by sputtering on the surface of a semiconductor substrate 1 of SrTiO3 containing boron as an impurity at an impurity concentration of 7 x 1013 pieces/cm3 to form an oxide superconducting thin film 9 with a thickness of about 7000 layers. . Next, when the focused electron beam is irradiated with an acceleration voltage of 6 keV, the oxide superconductor in the irradiated area f! The temperature of membrane 9 is 450
The temperature rises to about .degree. C., a phase change occurs and a specific resistance is exhibited, and an insulating layer 4 having a width of 50 mm is formed. By irradiating the portion where the insulating layer 4 is to be formed with the electron beam in this manner, a superconducting transistor having a shape as shown in FIG. 1 can be manufactured. At this time, the oxide superconducting thin film 9
Since the beam diameter is approximately 70 mm at the surface of the beam, a sufficiently weak superconducting coupling state can be formed.

The superconducting transistor fabricated as described above has an operating temperature of 85° C. or less, and exhibits voltage-current characteristics as shown in FIG. As voltage-current characteristics, characteristics a, b, c, d
However, this can be obtained by changing the voltage applied to the control electrode 3.

The conditions for the sputtering method were as follows.

Target: Er-Ba-Cu-0 sintered body, sputtering gas: Ar:02=1:1, deposition rate: 3 people/sec, heat treatment: 1 hour in 02 at 800''C.

Example 2 Using Y-Ba-Cu-0 oxide as a superconducting thin film material, an oxide superconducting thin film 9 was formed to a thickness of 6 by electron beam evaporation.
A superconducting transistor was manufactured using the same steps as in Example 1 except that about 1,000 transistors were formed. The operating temperature of the superconducting transistor thus obtained was below 80°C.

Note that the conditions for the electron beam evaporation method are as follows.

Evaporation materials: Y203, Cu, and BaO were evaporated independently using three electron beam guns, degree of vacuum: 2X10-'Torr, heat treatment: 1 hour in 02 at 850°C after evaporation.

Example 3 A superconducting transistor was manufactured using the same process as in Example 1, except that La-5r-Cu-0 oxide was used as the superconducting thin film material and an oxide superconducting thin film 9 was formed to a thickness of about 5000 by sputtering. Created. The operating temperature of the superconducting transistor thus obtained was below 20°C.

Note that the conditions for the sputtering method are as follows.

Target Ni La-3r-Cu-0 sintered body, Sputtering gas: Ar: 02 = l: 1, Vapor deposition rate: 3
Human/sec, heat treatment 1 hour in 02 at 7800°C.

(Effects of the Invention) As explained in detail above, in the superconducting transistor and the manufacturing method thereof of the present invention, the superconducting electrode, the control electrode, and the insulating layer are formed on the same plane of the semiconductor substrate, and any shape is possible. , can be manufactured by a relatively simple process.

In this way, since a large number of steps are not required, there is no need for disconnection of the vapor deposited layer and multiple mask alignments, and the yield is improved. Furthermore, since it has a flat structure, it is possible to create a multilayer structure and integrate it in the vertical direction, thereby achieving miniaturization.

[Brief explanation of the drawing]

FIG. 1 is a schematic top view showing an example of a superconducting transistor of the present invention, FIG. 2 is a sectional view taken along line A-B in FIG. 1, and FIG.
Cross-sectional view showing the manufacturing process of the superconducting transistor shown in Figure 4.
The figure shows a voltage-current characteristic diagram of the superconducting transistor of the present invention.
FIG. 5 is a sectional view showing a conventional superconducting transistor, and FIG. 6 is a sectional view showing another conventional superconducting transistor. 1, la, lb ...... Semiconductor substrate,
2.2a, 2b, 2c ・---Superconducting electrode, 3.3
a, 3b...Control electrode, 4.4a, 4b
, 4c --- Insulating layer, 5 . . .
・・・・・・・・・Impurity diffusion layer, 6 ・・・・・・・・・
・・・・・・・・・Channel layer. 7 ・・・・・・・・・・・・・・・Insulator, 8
・・・・・・・・・・・・・・・Weak bond, 9
・・・・・・・・・・・・・・・ Oxide superconducting thin film.

Claims (1)

[Claims] 1) A semiconductor substrate, at least two opposing superconducting electrodes provided in contact with the semiconductor substrate, and a current flowing between the superconducting electrodes provided in contact with the semiconductor substrate. a superconducting transistor, comprising: at least one control electrode for controlling the semiconductor substrate; and an insulating layer provided on one surface of the semiconductor substrate in contact with the superconducting electrode and the control electrode. 2) The superconducting transistor according to claim 1, wherein the superconducting electrode and the control electrode are made of an oxide superconducting thin film. 3) A method for manufacturing a superconducting transistor, comprising the step of forming an oxide superconducting thin film on a semiconductor layer, and then forming an insulating layer by changing the phase or composition of the oxide superconducting thin film. .