JPS63258081A - Method for producing superconducting materials - Google Patents

Abstract

PURPOSE:To be able to provide a finite resistance region adjacently to a superconducting region, which is nearly as high as an upper face of an oxide superconductor, by a method wherein a selected region of superconductive material or basic material thereof formed on a substrate is doped with impurity and thereafter subjected to heat treatment in oxidizing atmosphere. CONSTITUTION:A selected region of a superconductive material or a basic material 2 thereof formed on a substrate 1 is doped with impurity and thereafter subjected to heat treatment in oxidizing atmosphere for rendering Tco (temperature that resistance becomes zero) of the superconductive material low. For example, a material, which is turned into (YBa2)Cu3O6-8 after being formed into film, is provided on the insulating single-crystal substrate 1 consisting of SrTiO3 through sputtering for the formation of the basic material of the superconductive material, which is then annealed at temperature of 800-1000 deg.C in oxygen to be regenerated into the single-crystal superconductive material 2. Next, a photoresist 3 is selectively coated onto the upper face of the material 2 and a region 5 not coated with the resist is doped with silicon through ion implantation 4. Thereafter, calcination is performed in oxidizing atmosphere once again at temperature of 700-1000 deg.C so as to make Tco of an ion- implanted region 11 transfer to lower temperature side.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention provides a method for manufacturing functional elements using superconducting ceramics by selectively reducing Tco (the temperature at which the tlE resistance becomes zero).
The present invention relates to a method for producing different regions of the invention.

The present invention aims to fabricate an active region or a resistance element in one element when functional elements using superconducting ceramics are integrated on the same substrate.

"Prior Art" Conventionally, metal materials such as Nb and Ge have been used as superconducting materials. However, their Tco (temperature at which resistance becomes zero) is as low as 23, and an expensive maintenance stand is required for practical use.

In contrast, ceramic-based superconducting materials have attracted attention in recent years. This material was first reported by IBM's Zurich Research Institute as a Ba-La-Cu-0 (barak type) oxide superconductor.

However, these oxide ceramic superconductors were only made into bulk tablets.

Furthermore, since conventionally known metal superconductors are metal materials, even if they can be formed into thin films on a substrate, when trying to fabricate multiple functional elements such as Josephson elements, it is difficult to When operating the entire system, such as the active region or resistive elements, at a constant temperature (e.g., liquid nitrogen temperature), there was no attempt to artificially control the most necessary Tco or Tc onset for each element.

"Conventional Problems" In such conventional technology, a thin film is formed on a substrate,
In addition to using a superconductor that has zero resistance at a given operating temperature as a lead, resistors and active elements must be made for the entire system.

However, until now, only research has been conducted that seems to solve everything by simply increasing Tco.

The inventors of the present invention have discovered the possibility of using oxide superconducting materials in a manner completely different from that of conventionally known metal superconducting materials.

The present invention satisfies these objectives.

"Means to Solve the Problem" The present invention is particularly effective for oxide superconducting materials (single crystal or polycrystal). This oxide has conditions that exhibit superconductivity when oxidized, and furthermore, under this oxide condition, Tc.

(Generally, Tc onset does not change much, and T
It has been experimentally found that the co. The amount of change in Tco can be determined by selectively adding impurities to the superconducting material or its starting material, thereby increasing the Tc only in the added region.

found that it is possible to lower the

This region can have a large number of superconducting regions (also called transition regions) with so-called finite resistance, which have a temperature range between Tc oncent and Tco.

Furthermore, it was also possible to artificially control the non-superconducting region, which is a temperature region higher than Tc oncent.

The present invention relates to a single-crystal or polycrystalline (ceramic) superconducting material, the molecular formula of which is, for example, (Al-X
Bx) ycuzOw x = O~L y = 2~4
Preferably 2.5 to 3.5. z = 1.0 to 4.0, preferably 1.5 to 3.5 degrees, W-4, 0 to 10.0, preferably 6 to 8. In this formula, A is one or more elements in the ma group of the periodic table of elements, such as yttrium (Y).
Or lanthanoids. B is composed of one or more elements of Group IIa of the Periodic Table of Elements, and is, for example, barium (Ba).

In the present invention, a monocrystalline or polycrystalline thin film (generally having a thickness of 0.1 to 30 μm) represented by the general formula is formed on a substrate having an insulating surface.

and active elements such as Josephson elements,
Unnecessary parts other than passive elements such as resistors were removed by a known photolithography method. Furthermore, for the parts of the remaining superconducting material or its starting material that will become electrodes and leads, leave the mask as it is, or place a new mask, and apply the mask only to the area that should have finite resistance. Removed. Then, impurities were added to only the region without this mask by ion implantation.

Because this ion implantation method damages the crystal structure,
After this, heat treatment was performed in an oxidizing atmosphere.

Impurities include aluminum (At), magnesium (Mg), gallium (Ga), silicon (Si), germanium (Ge), titanium (Ti), and zirconium (Zr).

Iron (Fe), Niackel (Ni), Cobalt (Co),
Boron (B).

Phosphorus (P) is a typical example thereof, and one or more types thereof are used.

In addition, this impurity is 5×1O1' to 1×102'/cm
'The amount of injection was added.

Furthermore, after removing the mask material, 700 to 100
Oxidation was carried out at a temperature of 0° C., and an oxide of this impurity was formed in the added region by annealing to perform variable control of Tco. As a result, it has become possible to use the regions to which such impurities are not added as electrodes and leads, and the regions to which such impurities are added to serve as active regions or resistance regions.

In particular, annealing in an oxide atmosphere after ion implantation
The oxidation of the added impurity theoretically interferes with the superconducting properties, and the impurity insulates and forms a finite region of superconducting resistance and a non-superconducting region due to the addition.

"Function" Thus, it is possible to provide a finite resistance region adjacent to the superconducting region having approximately the same height as the top surface of a single-crystal or polycrystalline oxide superconductor provided on a substrate having an insulating surface. It became.

Furthermore, when this substrate is made of a silicon semiconductor with an insulating surface, it has become possible to make the interconnection leads and electrodes of a superconducting material and connect them to create a resistor.

The present invention will be described below with reference to Examples.

"Example 1" As an example of the present invention, a single crystal oxide superconductor was used. That is, a single crystal thin film was formed on an insulating single crystal substrate, such as strontium titanate (SrTiO+), using a sputtering method.

For example, (
A material was provided where YBaz)Cu30h=s. The top of this substrate was heated to 700 to 1000°C, for example 850°C.

This target was then sputtered to grow oxide ceramics on the substrate. The atmosphere used was a mixed gas of argon and oxygen.

In this way, an oxide material having a thickness of 0.1 to 1 μm was formed on the substrate. The starting material for the superconducting material was thus formed.

This was annealed in oxygen at 800-1000°C for 5-50 hours. They were then able to transform this thin film into a single-crystal superconducting material.

Curve (20) in FIG. 3 is the temperature-resistivity characteristic of such ceramics. In the drawings, Tc.

(22), Tc ONSEL-(21), and a transition region (a region that is superconducting but has finite resistance) (23).

Thus, as shown in FIG. 1(A), an oxide superconducting material (2) was produced on the substrate (1). Thereafter, a photoresist (3) was selectively coated on the upper surface.

As shown in FIG. 1(B), silicon is applied to the region (5) where the resist is not formed by 5×10” to 1×1QZ.
It was added by ion implantation method (4) at a concentration of 1 cm/cm, for example, 5 x 10" cm/cmff.

After this, the whole was heated again to 700 to 100 in an oxidizing atmosphere.
It was heated and baked at a temperature of 0°C. Then, the resist (3) also becomes carbon dioxide gas, water, etc. and is vaporized and removed. In addition, in the ion-implanted region (11), the implanted silicon becomes about 0% of the oxide (SiO□ or its modified product). .1χ is added to the region (10
) (The characteristics could be made the same as those shown in FIG. 3 (24)).

The temperature-resistivity characteristic of the oxide ceramic to which this impurity has been added is shown in FIG. 3 (20°).

That is, due to the addition of impurities, Tco (22) becomes Tco'
It can be seen that the temperature has shifted to the lower temperature side (22°).

Furthermore, this movement to the lower temperature side can be controlled by the amount of impurities added by ion implantation.

This impurity doped region (11) is 760 to 1000 below.
Even in high-temperature treatment steps at .degree. C., Tco' continued to be lower than the Tco of early superconducting ceramics.

"Example 2" FIG. 2 shows an embodiment of the present invention.

In the drawings, a substrate (1) is provided with transistors and the like and is a semiconductor substrate. Part of its surface has holes for electrodes (7
), and the other surface is an insulating film (6) having an insulating film, for example silicon nitride (9), on its upper surface. Semiconductor (1)
The insulating film (8) between the and silicon nitride (9) is silicon oxide.

An oxide superconducting material was formed on these upper surfaces by the same sputtering method as in Example 1. Patterning of electrodes, leads, and portions to be resistors was performed using a known photolithography technique. Furthermore, impurity ions were selectively added and implanted to produce a finite resistance region (11) according to Example 1. A superconducting region (10) with zero resistance connected to this,
(10') electrically connects this region to others. In this way, a lead/electrode region (10) with zero resistance at liquid nitrogen temperature (77 K) and a region (11) with finite resistance were constructed.

This oxide superconducting material was polycrystalline (ceramic).

This embodiment further includes a second insulating film (9°) on this upper surface.
was formed of silicon nitride, and the recess was filled with another insulator (12). After forming an opening (7″), a superconducting material is formed again in the same manner as in Example 1, and patterned using photolithography to form electrodes and leads (13).
was constructed.

In this way, multilayer wiring could be formed on the semiconductor integrated circuit board.

"Effects" In contrast to the conventional use of superconducting materials only as leads with zero resistance, the present invention adds impurities to such strong conductive materials to shift Tco from its initial state.
It was controlled to have the desired finite resistance at the desired operating temperature (eg, liquid nitrogen temperature).

In this way, as an application of this method, it became possible to make the active region of an active element, a resistor, etc. from the same main component material, and the upper surface of each region could be configured to be approximately the same surface, making multilayer wiring possible.

In the present invention, it is possible to use not only the sputtering method but also the printing method, the MBε (molecular epitaxial growth) method, and the vapor phase method as a method for producing the oxide superconducting material.

[Brief explanation of drawings]

FIG. 1 shows the manufacturing steps of the impurity addition method of the present invention. FIG. 2 shows an embodiment of the invention. FIG. 3 shows the characteristics of the superconducting material obtained by the present invention.

Claims (1)

[Claims] 1. After adding impurities to a selected region of a superconducting material formed on a substrate or its starting material, the Tco of the superconducting material (
A method for producing a superconducting material characterized by lowering the temperature at which the resistance becomes zero. 2. In claim 1, the impurity elements are aluminum (Al), magnesium (Mg), gallium (Ga), silicon (Si), germanium (Ge).
, titanium (Ti), zirconium (Zr), iron (Fe
), nickel (Ni), cobalt (Co), boron (B
), phosphorus (P), and phosphorus (P). 3. In claim 1, the impurity is 5×10
A method for producing a superconducting material, characterized in that it is added at a concentration of ^1^5 to 1x10^2^1/cm^3.