JPS63245827A - Forming method for oxide group superconductive thin film - Google Patents

Abstract

PURPOSE:To obtain an oxide group superconductive thin film whose critical temperature is high by forming an oxide film made of elements L, Cu, and O and next implanting an element M by an ion implantation or gas diffusion method. CONSTITUTION:When an oxide group superconductive thin film made of L-M-Cu- O (where L=Y, Sc, La, and M=Ba, Sr, Ca) is formed, sputter equipment 4 composed of a sputter chamber 1, a high frequency power source 2, and an evacuation device 3 is prepared and used. A Y2O3 block 11 and a CuO block 12 are combined to form a target 13 in a disc shape so that their area ratio is 1 : 1, and then Y-Cu-O oxide is formed on a Si substrate 14. In succession, this sample is taken out from the sputter equipment 4 and an ion implantation device is used to accelerate ionized Ba elements and implant them inside from the surface of the sample and next heat treatment is performed for this sample. An oxide group superconductive thin film which has a high critical temperature Tc can be easily formed accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Field of Industrial Application) The present invention relates to a method for producing an oxide-based superconducting thin film that can be applied to the production of superconducting transistors.

(Prior Art) Currently, high-density, high-speed semiconductor devices are being developed using St, GaAs, and the like. However, for example, S
This is because the heat generation in the i-element reaches several ff1w.

As the degree of integration advances to 4 megabits and 16 megabits, the issue of how to deal with the heat generated by the elements has become a major hurdle.

As an element that has solved the problem of heat generation, there is a Josephson element that utilizes the Josephson effect, which is one of the superconducting phenomena. The amount of heat generated by this Josephson element is about 1 μW, which is three to four orders of magnitude smaller than that of a Si element. Moreover,
The switching speed is also several p-10 psec, three to four orders of magnitude faster than Si devices. Currently, the materials used to construct Josephson elements are:

Nb, NbN, etc. are used. However, Nb
Because NbN films are highly active, they easily combine with oxygen, and are unstable in the atmosphere. Furthermore, it is difficult to homogeneously produce an insulating film (barrier film) several tens of times thick, which is required for Josephson devices. Very difficult. Furthermore, since these materials have a low critical temperature Tc, there is a problem in that liquid helium, which is expensive and difficult to handle, must be used as a refrigerant. Also, the Josephson element.

Since it is a two-terminal element, there are also problems such as it being difficult to use compared to the three-terminal system (electric field control system) with 81 elements.

Therefore, recently, an element that eliminates many of the drawbacks of the above-mentioned Josephson element, ie, a superconducting transistor that combines a superconductor and a semiconductor, has been proposed. This superconducting transistor uses a three-terminal system and has power consumption and switching characteristics comparable to those of a Josephson element. However, even with superconducting transistors, they have not yet been put into practical use because they require the use of liquid helium, which is expensive and difficult to handle, as a coolant, and the superconducting part is easily oxidized and unstable. This is the actual situation.

By the way, recently, the degree of kneading, that is, the critical temperature Tc, has been found to be higher than the liquid nitrogen temperature. For example, Y-Ba-Cu-0
Oxide-based superconductors, represented by , have been developed. If this oxide-based superconductor is incorporated into a superconducting transistor, the above-mentioned problems such as easy oxidation and the necessity to use liquid helium can be solved.

However, the oxide-based superconductors currently proposed are all sintered bodies obtained by baking and solidifying powder, and it has been difficult to apply them to superconducting elements as they are.

(Problems to be Solved by the Invention) As mentioned above, oxide-based superconductors represented by Y-Ba-Cu-0 are superior superconductors in various aspects compared to conventional Nb and NbN. be. However, the technology for producing thin films of this oxide-based superconductor has not been established.
For this reason, there was a problem that it could not be applied to superconducting transistors and the like.

Therefore, an object of the present invention is to provide a method for manufacturing an oxide-based superconducting thin film that can be applied to manufacturing superconducting elements such as superconducting transistors.

[Structure of the invention] (Means for solving the problem) In the present invention, two compositions are L-H-Cu-0 (however, L-
Y.

To produce an oxide-based superconducting thin film consisting of Sc, La, M=Ba, Sr, Ca), an oxide film consisting of one element, Cu, and O is fabricated, and then this film is subjected to ion implantation or The element M is implanted by gas diffusion.

(Function) An essential requirement for the LM-Cu-0-based oxide to become a superconductor is the presence of a 1M element. This is Y-Ba-Cu-0
In the system, it corresponds to Ba. Although Y-Cu-0 does not become a superconductor, the addition of Ba suppresses lattice instability and increases the amount of trivalent Cu3+ ions, resulting in a material with a high critical temperature Tc. In the sintering method.

It is easy to make the distribution of Ba uniform. but.

As mentioned above, thin films cannot be produced using the sintering method. Furthermore, even if a sputtering method using Y-Ba-Cu-0 as a target is used, the distribution of Ba in the film becomes non-uniform and a high critical temperature Tc cannot be obtained.

In the present invention, after producing an oxide film consisting of the two elements Cu and O, the element H is injected into this film by ion implantation or gas diffusion.
can be injected evenly.

This makes it possible to produce an oxide-based superconducting thin film with a high critical temperature Tc.

(Example) Examples will be described below.

Example 1 As shown in FIG. 1, a sputter chamber 1 is provided.

Sputtering device 4 consisting of a high frequency power source 2 and an exhaust device 3
was prepared and this spa treatment device 4 was used.

The target 13 is a Y2O3 block 11 and a CuO block 12 combined in a disk shape with an area ratio of 1:1, and Y-Cu is deposited on the SI substrate 13.
-0 oxide was produced to a thickness of 1 μm. In addition.

The conditions at this time were: discharge power 200W, gas composition Ar
-50%02. The gas pressure was 5xlO' torr.

Next, this sample is taken out from inside the sputtering apparatus 4.

Ionized Ba was accelerated using an ion implantation device and injected into the sample from the surface. Thereafter, the sample was heat treated at 500°C for one day.

When the resistance change with respect to temperature of the sample thus obtained was investigated, as shown in FIG. 2, the resistance began to decrease at 93 and completely became zero at 85.

That is, a good Y-Ba-Cu-0 superconducting thin film was obtained.

Example 2 In the same manner as in Example 1, 1 μm thick Y-C was deposited on the 81 substrate.
A u-0 film was prepared. This sample was placed in a diffusion furnace for 80 minutes.
The chamber was heated to 0° C. and filled with Ba vapor for one day of heat treatment.

When the resistance change with respect to temperature was examined for the sample thus obtained, the resistance began to decrease at 100 K and completely became zero at 92 K, confirming that the manufacturing method of the present invention is effective.

Note that the present invention is not limited to the embodiments described above. That is, in the above-described embodiment, Y (yttrium) and Ba (barium) are combined, but according to the present invention, Y and Sr (strontium) or Ca
(Calcium) combination.

Similarly, a good superconducting thin film can be produced using a combination of Sc (scandium) and any one of Ba, Sr, or Ca, or a combination of La (lanthanum) and any one of Ba, Sr, or Ca.

[Effect of the invention] As described above, according to the method of the present invention, a high critical temperature T
It is possible to easily produce an oxide-based superconducting thin film having c, thereby providing a method for producing an oxide-based superconducting thin film that can be fully applied to the production of superconducting elements such as superconducting transistors.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a sputtering apparatus used to carry out the production method of the present invention, and FIG. 2 is a diagram showing an example of resistance change characteristics with respect to temperature of a superconducting thin film produced by the production method of the present invention. 11...Y2O3 block, 12...CuO block. 13...Target, 14...81 board. Applicant's agent Patent attorney Takehiko Suzue CSJf-0

Claims (2)

[Claims] (1) The composition is LM-Cu-O (where L=Y, Sc
, La, M=Ba, Sr, Ca), after producing an oxide film consisting of elements L, Cu, and O, this film is subjected to ion implantation or gas A method for producing an oxide-based superconducting thin film, characterized in that element M is implanted by diffusion. (2) The method for producing an oxide-based superconducting thin film according to claim 1, wherein when the element M is implanted by ion implantation, a heat treatment is performed after the implantation.