JPS63208284A - Superconductive device - Google Patents

Abstract

PURPOSE:To omit a heating step, to simplify the manufacturing process and to improve the reproducibility of the characteristics of a device, by constituting a conductor layer with metalloid or alloy including the metalloid. CONSTITUTION:A normal conductor 13 is which is a superconductor layer, is provided in a superconductor electrode 14 constituting a superconductive device. For the conductor 13, a thin film comprising metalloid or alloy including the metalloid as a component is used instead of a conventional single crystal semiconductor. In detail, Bi or alloy of Bi and Sb is used. In this way, a superconductive device such as a superconductive transistor or Josephson element can be implemented without introducting a heating step intended for improving the crystalline property of a semiconductor. Therefore, not only the superconductive devices can be readily manufactured, but also circuits having high integration density can be implemented by three-dimensional integration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a switching element that operates in a cryogenic environment, and particularly to a superconducting device that is excellent in high-speed operation and low power consumption.

[Background of the invention]

Conventionally, in the technical field related to superconducting devices that operate at extremely low temperatures, superconducting devices having a structure in which a pair of superconducting electrodes are coupled via a half body have been described, for example, in Journal of Applied Physics, 1980, Vol. 51,
Page 2736 (Journal of Applie
d Physies vol, 51 (1980) p.
, 2736, C1ark. It is known that Si, InAs, etc. can be used as semiconductor materials. Moreover, single crystal materials are used as these semiconductor materials.

[Problem that the invention seeks to solve]

In a superconducting element using semiconductor bonding, in a method in which a single crystal material is used as the semiconductor, a semiconductor single crystal in the form of a substrate or a semiconductor single crystal in the form of a thin film is used. In the latter case, a semiconductor single crystal grown in the form of a thin film is used, or an amorphous or polycrystalline semiconductor thin film is formed and then heated by high frequency application or laser beam irradiation. It was used as a crystalline semiconductor. When using these methods, it is necessary to heat part or all of the sample, and the superconducting properties of the superconducting material change due to the effects of heat. It has been difficult to realize a circuit including a superconducting device such as a superconducting transistor that is three-dimensionally integrated by stacking semiconductor single crystals.

An object of the present invention is to solve the problems of these conventional techniques and provide a superconducting device that can be three-dimensionally integrated, and a superconducting integrated circuit using the same.

[Means for solving problems]

In the present invention, in order to achieve the above-mentioned object of the present invention, a semiconductor layer is used as a normal conductor, which is a superconductor layer provided between superconducting electrodes constituting a superconducting device, in place of a conventional single-crystal thin film semiconductor. It is characterized by the use of a thin film made of metal or an alloy containing metal as a component. More specifically, Bi
, or an alloy of Bi and Sb.

[Effect]

In the prior art, the mobility of the semiconducting material is increased by improving the crystallinity of the semiconductor.
By increasing the superconducting coupling between superconducting electrodes placed in contact with the semiconductor through the semiconductor, we can increase the amount of superconducting current that can flow through this area.

It was necessary to make it large enough to realize rotational movement. For this reason, when Si or Ga is used as a semiconductor material, it is generally essential to improve crystallinity by heating.

Furthermore, when using compound semiconductors, molecular beam growth can be used, but it is difficult to overlay a superconductor or insulating film and grow a high-quality single crystal with a uniform composition on top of the superconductor or insulating film. Met.

Therefore, the problem with these conventional technologies is that a thin film with a uniform composition and high carrier mobility can be made without heating as a material to be provided between superconducting electrodes, and the conductivity is increased by the electric field effect. It is necessary to be able to change the

As a material that satisfies these requirements, Bi
It was also found that an alloy of Bi and sb can be used.

Bi and alloys of Bi and sb can be formed into thin films without excessive heating of the sample, and have a mobility of 10” rrr/V.
-S and a sufficiently large value can be obtained to realize a superconducting device.

In addition, the composition range of the alloy of Bi and sb is s
It is desirable that the composition of b is 40% or more. moreover,
It is preferably within the range of 7 to 20%. This means that in this composition range, the B1-sb alloy has a semimetallic or semiconductor-like electron energy band structure, and 0
This is because in the range of sb concentration from about 5% to about 5%, it behaves as a semimetal with overlapping bands, and in the range from about 5% to about 40%, it behaves as a semiconductor with a gap in the electron energy structure. In such cases, B i
-Sb alloy can be used as a material constituting the superconducting device in the present invention. Especially the composition of sb is about 7%~
In the range of about 20%, the energy and
The value of the gap is in the range of 5 meV to 15 meV, which is about the same as the energy gap that occurs in the superconductor, and with a voltage amplitude of this order as the reference voltage that corresponds to the energy gap that occurs in the superconductor. It is possible to obtain an energy gap value suitable for a semiconductor for use in a working device.

As described above, according to the present invention, superconducting devices such as superconducting transistors or Josephson elements can be realized without introducing a heating process for the purpose of improving the crystallinity of semiconductors. Not only will this make it easier, but it will also be possible to integrate three-dimensionally and realize highly integrated circuits.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples. First, a first embodiment of the present invention will be described using FIG. S
The surface of the i-substrate 11 is thermally oxidized to a thickness of 300 nm.
An insulating film 12 made of T is formed. Subsequently, a film with a thickness of 150 mm made of B1-12 wt% sb alloy is formed by resistance heating vapor deposition.
A normal conductor thin film 13 having a thickness of 1 nm was formed and processed by a lift-off method. Next, a superconducting thin film made of Nb having a thickness of 1100 nm is formed and processed by a reactive ion etching method using CF4 gas to form a superconducting electrode 14. Next, a Si film with a thickness of about 30 nm was grown by chemical vapor deposition.
A gate insulating film 15 made of O2 is formed, and finally an All! film with a thickness of about 60 nm is formed. By producing the gate electrode 16 made of a vapor deposited film, the superconducting device of the present invention could be realized. This superconducting device is heated at liquid helium temperature (4.2K).
) When a positive voltage was applied to the gate electrode, the value of the superconducting current flowing between the opposing superconducting electrodes via the B1-1.2 wt% sb alloy was increased. was completed. In this example, Nb was used as the material of the superconducting electrode, but instead of this, pb,
PB gold alloy also NbN.

Needless to say, Nb compounds such as NbaGe, Nb5sn, NbaSi, etc., or M o N may also be used.

A second embodiment of the present invention will be described with reference to FIG. The semiconductor substrate 21. has exactly the same material and structure as the first embodiment of the present invention. Insulating film 22, normal conductor thin film 23
．． Superconducting electrode 24. Gate insulating film 25. Gate electrode 26
A field-effect superconducting device is formed. This device corresponds to one of the devices forming the first layer integrated circuit formed on the semiconductor substrate 21. Next, an interlayer insulating film 27 made of 5 iOz and having a thickness of about 2 μm is formed by chemical vapor deposition. Next, the thickness is about 200n.
A second normal conductor thin film 29 made of a B1-12wt% sb alloy of m and a superconducting electrode 28 made of a Nb vapor-deposited film with a thickness of about 200 nm are formed. The superconducting electrodes 28 are superconductingly coupled via a normal conductor thin film 29 to form a quasi-planar Josephson element. This Josephson junction element is one of the devices constituting the second layer integrated circuit. Finally, a protective film 30 made of SiO2 with a thickness of approximately 2 μm was formed by chemical vapor deposition, thereby making it possible to realize the superconducting device of the present invention and an integrated circuit including the same. In this embodiment, one semiconductor substrate 2
A two-layer integrated circuit is fabricated on the first layer, and the first layer is electrically connected to operate. It goes without saying that the number of layers for integration may be two or more, but in any case, since excessive heating is not involved, integrated circuits can be realized with good reproducibility and high yield. Ta.

〔Effect of the invention〕

As described above, according to the present invention, a heating process is not required when manufacturing a superconducting device and an integrated circuit including the same, so the manufacturing process is simplified.
In addition to excellent reproducibility of device characteristics,
It is possible to easily produce a three-dimensionally integrated circuit, which has the effect of realizing a high degree of integration.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a portion of a superconducting device according to a first embodiment of the present invention, and FIG. 2 is a sectional view showing a portion of a superconducting integrated circuit according to a second embodiment of the present invention. 11.21...Semiconductor substrate, 12.22...Insulating film, 13.23,29...Normal conductor thin film, 14,24°28...Superconducting electrode, 15,25...Goo 1 ~Insulating film, 16.26... Gate electrode, 27... Interlayer insulating film, 30... Protective film. Agent: Patent Attorney Katsuo Ogawa (Parent)

Claims (1)

[Claims] 1. At least one pair of superconducting electrodes that operate at extremely low temperatures;
It is configured to have a conductor layer in contact with the dielectric electrode, and a control electrode provided on the conductor layer between the superconducting electrodes. ,
A superconducting device for controlling the magnitude of superconducting coupling between superconducting electrodes, wherein the conductor layer is made of a semimetal or an alloy containing the same. 2. The superconducting device according to claim 1, wherein the material constituting the conductor layer is Bi or an alloy of Bi and Sb.