JPS61269385A - Superconductive device - Google Patents

Abstract

PURPOSE:To make the device planar, by providing with two impurity introduced sections for reducing Schottky barrier on a semiconductor substrate, and by making a low-concentration impurity layer between them, being a thickness such that the layer can not project from the surface of a superconductive electrode. CONSTITUTION:After an oxide film 2 is formed on a semiconductor substrate 1, a protrusion 3 is formed by etching. After impurities are diffused into the entire face to form a diffusion layer 4, an Nb film is evaporated. Next, the Nb film is treated, using a photo resist pattern as a mask to form superconductive electrodes 5, 6. In this way, since the surfaces of the protrusion 3 and the superconductive electrodes 5, 6 are made into approximately same heights, this device can be made planar. Thereafter an insulating film is formed and then a control electrode 8 is formed.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a switching device that operates at extremely low temperatures, and particularly to a superconducting device that increases circuit gain and is suitable for manufacturing integrated circuits. Regarding structure.

[Background of the invention]

A Josephson element is known as a conventional switching device that operates at extremely low temperatures. The switching speed of this Josephson element is fast.

In addition, the power consumption is small at a few μW, but Josephson elements are basically two-terminal devices, so the technology that has been accumulated with conventional semiconductor transistors cannot be used in the circuit configuration, and There are two known superconducting devices that require the use of a power source and are at risk of solving this problem: The first is iTriple E Transaction on Magnetics (IEEE
τtransaction Magnati, cs)
There is a superconducting device using quasiparticles called "Quitaron" published in MA G-19, 1983, page 1293. In this device, the lifetime of the quasiparticle limits the switching speed, so the element structure has to be special to increase the switching speed. The second is Journal on Applied Physics, Volume 51, Volume 1.
“Josephson Field Effect Transistor” (Josepson Field Effect Transistor) published in 980, page 2736
aphson Field Effect Trons
There is a superconducting device disclosed in a paper titled . In this device, the control electrode was not completely electrically isolated from the channel layer, and therefore it was difficult to increase the current gain6.
In the prior art, superconducting devices with sufficient performance to construct large-scale digital integrated circuits have not always been provided.

[Purpose of the invention]

An object of the present invention is to provide a structure of a superconducting device which has a planarized structure and has a high gain and is therefore suitable for application to integrated circuits.

[Summary of the invention]

In the superconducting device of the present invention, in order to flatten the device and improve gain, two impurity introduction regions for reducing the Schottky barrier and a low impurity concentration region between them are provided on the semiconductor substrate, and a low impurity concentration region is provided on the semiconductor substrate. A feature of the device is that the concentration portion is formed in a protrusion that is about the same thickness or thinner than the superconducting electrode provided on the semiconductor, thereby flattening the device.

[Embodiments of the invention]

The present invention will be explained in detail below using examples.

FIG. 1 is a sectional view showing a part of a superconducting device according to an embodiment of the present invention. Impurity concentration 1×IQ14cm-”
After oxidizing the surface of a Si substrate 1 containing the following boron as an impurity to form an oxide film 2 made of SiO with a thickness of 30 nm, a photoresist pattern was formed on it, and using this as a mask, CF, The surface of the Si substrate is etched by plasma etching using a gas or ion beam etching using a gas such as Ar @ CF 4 to form protrusions 3 . The height of the protrusion, that is, the amount of etching of the Si substrate is preferably 200 nm in this embodiment, which is the same as or smaller than the thickness of the superconducting electrode to be formed later. Further, the width of the protrusion is 0.
The thickness is preferably selected to be 3 to 0.1 .mu.m. Subsequently, boron is diffused over the entire surface of the sample at a surface concentration of 1.times.10 "am-" to form a diffusion layer 4. The purpose of this embodiment can be achieved by using the ion implantation method rather than the diffusion method for forming the diffusion layer 4. In this example, the thickness of the diffusion layer is 5 mm from the surface.
It was formed to have a thickness of about 0 nm. In the protrusion, the diffusion layer is formed from both sides, leaving a part with low impurity concentration in the center.
Nbg is deposited to a thickness of about 200 nm by electron beam heating in a high vacuum of less than lXl0-''Pa. This Nb film is processed by plasma etching using CF4 gas using the photoresist pattern as a mask, and superconducting electrodes 5 and 6 are formed.
get. The protrusion 3 and the superconducting electrodes 5 and 6 are formed at a thickness of 50 nm using zero-order vapor phase epitaxy, which allows the device to be planarized.

After a film was formed and processed by plasma etching to form an insulating film 7, a control electrode 8 was formed by vacuum evaporation of Nb and processing by plasma etching, completing the superconducting device of the present invention. SiO,
The film can also be formed by sputtering instead of vapor phase growth.

When an integrated circuit was fabricated using this superconducting device and operated after being cooled to liquid helium temperature (4.2 K), the impurity concentration in the portion corresponding to the channel of the single superconducting device was found to be I x 1. In addition to being as low as O"cn-", there is a diffusion layer on the semiconductor side in the corrosion area between the superconductor and the semiconductor, so superconducting electrons easily seep into the semiconductor, and By applying a voltage of
I was able to double the amount. Furthermore, since the device is flattened as mentioned above, it is possible to form a three-dimensional structure with multiple layers of wiring extending to the control electrode and other wiring layers to connect them, resulting in a high level of integration. We were able to achieve this and achieve a high manufacturing yield. Also 1
In this embodiment, since the oxide film 2 is formed in advance to constitute the gate insulating film, the interface state can be reduced and the operation of the device can be stabilized. In addition, in this example,
Although Si was used as the semiconductor material, GaAs was used instead.
It goes without saying that materials such as , InAs, InP, and InSb may be used.Also, although Nb was used as the superconducting material, a pb gold alloy, NbN, Nb, Sb, etc. may be used instead.
i, Nb, AI2. Nb, Nb compounds such as Sn, M
Similar effects could be obtained using Mo compounds such as oN. Moreover, the type of impurity may be replaced with boron, such as phosphorus, arsenic, antimony, etc.

Further, although it is preferable to use impurities of the same conductivity type as the substrate, the effects of the present invention can be obtained even if impurities of different conductivity types are used.

〔Effect of the invention〕

As described above, according to the present invention, the magnitude of the superconducting current in the device can be changed up to about 100 times, so there is an advantage that the gain of the device can be improved. In addition, since the device is flattened, it is easy to form a three-dimensional wiring layer on the top, and therefore, when the degree of circuit integration is increased, disconnection of wiring at the recessed part can be prevented. Therefore, there is an advantage that a high manufacturing yield can be obtained.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] 1. A semiconductor protrusion provided on a semiconductor substrate, a first insulating film provided on the top of the protrusion, and a protrusion having a thickness equal to or greater than the height of the protrusion; two or more superconducting electrodes formed on a side surface of the part, a second insulating film formed on the first insulating film, and a second insulating film formed on the first insulating film;
a control electrode provided on an insulating film, and the protrusion is formed so that its side surface has a higher impurity concentration than that of the substrate.