JPH02260676A - Manufacture of superconductor device - Google Patents

Abstract

PURPOSE:To make an interelement isolation possible without exposing the side face of a superconductive region by a method wherein a metal film whose main component is precious metal and another metal film whose main component is lead are formed on a superconductor film, and an insulator is formed through a reaction between lead and the superconductive film. CONSTITUTION:An Ln-M-Cu-O (Ln, rare earth element; M, alkali earth metal) oxide superconductor film 2 is formed on an insulating substrate 1, a resist film 3 is formed thereon excluding a part which is left as a superconductive region to form a mask pattern. A metal film whose main component is precious metal is formed on the whole face of the substrate 1. The whole substrate 1 is dipped into an organic solvent such as acetone or the like to remove the film 3 by dissolution. Next, lead is evaporated on the whole faces of the films 4 and 2 to form a metal film 5. The thickness of the film 5 is made 35-65% of that of the film 2. Lead and the superconductor film 2 are made to react with each other to form an insulator. Then, the metal film 5 formed on the film 4 is removed. By this setup, the part of the film 2 covered with the film 4 grows to be a superconductive region 7, and the insulating material 6 around the region 7 carries out an interelement isolation serving as a field region 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for manufacturing a superconductor device using an oxide superconductor such as a Y-Ba-Cu-0 system.

(Prior Art) Many superconducting materials whose electrical resistance becomes zero below a certain temperature have been discovered, and various attempts have been made to realize electronic devices using them. In addition, various so-called high-temperature superconductors having transition temperatures higher than the boiling point temperature of liquid nitrogen have recently been discovered, and attempts to realize superconducting devices that do not require expensive liquid helium have attracted interest.

The high temperature superconductor mentioned above has a transition temperature of liquid nitrogen temperature (
-77K) defective perovskite-type oxide superconductors with oxygen defects represented by the Y-Ba-Cu-0 system, as well as the B1-8r-Ca-Cu-0 system and Tl-Ba- Ca-Cu-0-based oxide superconductors have been discovered, and defective perovskite-type oxide superconductors, represented by Y-Ba-Cu-0, are easy to handle and are suitable for device development. It is attracting attention as a suitable material.

Generally, in order to fabricate electronic devices using superconducting materials, a thin film of superconducting material is formed on an insulating substrate by sputtering, etc., and is patterned, leaving areas to be used as element regions and wiring, etc. Additional processing, film formation, mutual wiring, etc. are performed as necessary to complete the desired device. Therefore, a so-called device isolation technique, in which a superconducting thin film formed on an insulating substrate is first accurately patterned to electrically insulate and isolate device regions from each other, is essential.

However, in the case of highly oriented materials such as Y-Ba-Cu-0 based oxide superconductors, it is difficult to completely remove the regions (field regions) other than those used as element regions or wiring using normal etching methods. When isolation is performed between elements by This was reflected in the device characteristics and became a factor causing instability of the device characteristics.

In contrast, the present inventors have previously discovered that it is possible to make an insulating material by reacting a Y-Ba-Cu-0 based oxide superconductor with pb, and using this, the -A metal film containing lead as a main component is formed on the Ba-Cu-0 based oxide superconductor film in the field area, and the oxide superconductor in the field area is insulated. It is proposed to perform separation between

(Problems to be Solved by the Invention) According to the above-described inter-element isolation method by insulating the Y-Ba-Cu-0 based oxide superconductor with lead, the side surfaces of the oxide superconductor in the superconducting region are exposed. This is a very effective method for isolating elements, as it has the advantage of being able to perform element isolation without causing any interference, and achieving constant superconducting properties.

By the way, when forming a field region by reacting a lead film and an oxide superconductor film in this way, Y-Ba-Cu
- Since wet etching cannot be applied to the 0-based oxide superconductor, and the etching rates for dry etching of the lead film and the oxide superconductor film are almost the same, the prerequisite patterned lead film can be obtained. Therefore, a so-called lift-off method must be used.

However, when patterning a lead film by the lift-off method, there are many restrictions regarding the shape.

In other words, when it is desired to form a superconducting region as a fine pattern, a mask pattern must be formed in a minute area corresponding to the portion to be left as a superconducting region. A lead film is formed up to the point where a so-called bridge is easily formed between the upper and lower films. For this reason, there have been problems in that the reproducibility of the lead film pattern is poor, such as it being difficult to dissolve and remove the mask material, and even if the mask material is removed, a fine pattern cannot be formed due to bridges. Although this problem can be alleviated by increasing the thickness of the mask material, a problem arises in that increasing the thickness of the mask material makes it difficult to form a fine pattern.

In other words, the larger the portion left as the superconducting region, the better the separation between elements can be performed, and conversely, the finer the superconducting region, the lower the reproducibility. This is contrary to the current situation where the goal is to miniaturize the element area and achieve high integration.

The present invention has been made to address these issues, and provides a superconductor that allows separation between elements without exposing the side surfaces of the superconducting regions and that makes it possible to obtain fine superconducting regions with good reproducibility. The purpose is to provide a method for manufacturing the device.

[Structure of the Invention] (Means for Solving the Problems) In other words, the method for manufacturing a superconductor device of the present invention comprises manufacturing an Ln-M-Cu-0 based oxide superconductor (Ln is selected from rare earth elements) on an insulating substrate. and M represents at least one element selected from alkaline earth elements. A step of forming a first metal film containing a noble metal as a main component according to the shape and shape of a desired superconducting region, and forming the Ln-M film continuously on the first metal film containing a noble metal as a main component. - a step of forming a second metal film mainly containing lead on the Cu-O based oxide superconductor film; The method is characterized by comprising a step of reacting with the Ln-M-Cu-0 based oxide superconductor film to form an insulating material.

(Function) In the present invention, first, a first metal film containing a noble metal as a main component is formed on a portion of the Ln-Cu-0 based oxide superconductor film that is desired to remain as a superconducting region by, for example, a lift-off method; A second metal film containing lead as a main component is formed on this. Then, by reacting the portion of the Ln-Cu-0 based oxide superconductor that is not covered with the first metal film containing a noble metal as a main component and the second metal film containing lead as a main component, A good insulating material having the same height as the superconducting region can be obtained, and since the superconducting region is protected by the first metal film containing noble metal as a main component, that state is maintained. Further, since the first metal film containing a noble metal as a main component can be formed in advance in the portion to remain as a superconducting region by a lift-off method or the like, even if the pattern of the superconducting region is miniaturized, it can be formed with good reproducibility.

Note that it is sufficient to form the second metal film mainly composed of lead around the first metal film mainly composed of a noble metal.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing the manufacturing process of a superconductor device according to an embodiment of the present invention.

First, a 0Ln-M-Cu-0 based oxide superconductor thin film 2 is formed by about 5000 people on an insulating substrate 1 using a thin film formation method, and then PE
A mask pattern made of a photoresist film 3 is formed using the P method (FIG. 1-a).

The insulating substrate 1 used is an MgO substrate, 5r710.
Examples include a LITaJ substrate, a LINbOx substrate, a Y-stabilized ZrO2 substrate, or a structure in which these materials are formed on a Si substrate.

The Ln-M-Cu-0-based oxide superconductor may be any material as long as it can realize a superconducting state, such as Ln-M-Cu-0-based oxide superconductor.
M CuO (Ln is Y, La5ScSNd,
5s12 3 7-δ 1EuSGd, Dy% llo, Er, Tm,
At least one element selected from rare earth elements such as Yb and Lu, and H is Ba.

Indicates at least one element selected from alkaline earth elements such as Srs Ca, and δ represents an oxygen defect, usually 1.
The following numbers, part of Cu is Tl5V s Cr, Mn,
re.

Can be replaced with Co, Nl, Zn, etc.' ), a defective perovskite type with oxygen vacancies, 5r-Ln-
An oxide superconductor having a perovskite structure in a broad sense, such as a layered perovskite type such as Cu-0 type, is used. Typical systems include, in addition to the Y-Ba-Cu-0 system, systems in which V is replaced with a rare earth element such as ELISHO% Yb.

Further, the method for forming the Ln-Cu-0 based oxide superconductor thin film 2 includes electron beam evaporation, laser evaporation,
Various thin film forming methods can be used, such as magnetron sputtering, ion beam sputtering, and cluster ion beam methods.

Next, the Ln-M-Cu film on which the photoresist film 3 was formed
A noble metal such as silver, gold, or platinum is applied to the entire surface of the −0-based oxide superconductor thin film 2 by a thin film forming method such as a vacuum evaporation method.
About 500 people deposited the film to zero thickness to form the first metal film 4 mainly made of noble metal (FIG. 1-b).

Next, by immersing the whole in an organic solvent such as acetone, the photoresist film 3 is melted and removed, and the first metal film 4 on the photoresist film 3 is also removed, and the Ln covered with the photoresist film 3 is removed. - The surface of the M-Cu-0-based oxide superconductor thin film 2 is exposed, and the first metal film is formed only on the Ln-M-Cu-0-based oxide superconductor thin film 2 in areas where no mask pattern was present. 4 will remain (Figure 1-○).

The region covered with the remaining first metal film 4 is a portion that will eventually become a superconducting region, and a mask pattern is formed excluding this portion that will become a superconducting region, so that the superconducting region is, for example, a line When the width is miniaturized to 1 μm, the area where the photoresist film 3 is formed becomes relatively large, and the first metal film 4 that becomes the superconducting region can be precisely patterned.

Next, Ln-M-
A second metal film 5 made of lead is formed by depositing lead on the entire surface of the Cu-0 based oxide superconductor thin film 2 by a thin film forming method such as vacuum evaporation to a thickness of about 2,500. Figure 1-d).

The thickness of the second metal film 5 made of lead to be formed is 35% to 65% of the thickness of the Ln-Cu-0 based oxide superconductor thin film 2.
% range is preferable. The thickness of the second metal film 5 is 3 times the thickness of the Ln-Cu-0 based oxide superconductor thin film 2.
If it is thinner than 5%, it becomes difficult to completely convert the Ln-M-Cu-0 based oxide superconductor thin film 2 into an insulator by that thickness, and the Ln-M-Cu-0 based oxide superconductor thin film 2 This is because if it is thicker than 65% of the thickness of the thin film 2, unreacted lead remains on the surface, making isolation between elements incomplete.

Next, the second metal film 5 made of lead and the portion of the Ln-Cu-0 based oxide superconductor thin film 2 which is directly in contact with the second metal film 5 made of lead are caused to react with each other to form a field region, thereby forming an insulating material 6. (Figure-e). Note that during this reaction, the Ln-
Since the M-Cu-0 based oxide superconductor thin film 2 is prevented from reacting with lead, the initial film quality can be maintained.

This reaction between lead and the Ln-M-Cu-0 based oxide superconductor can also proceed by leaving it in the air at room temperature for 12 to 24 hours, but the reaction can also be progressed by leaving it in the air at room temperature for 12 to 24 hours. This can be accelerated by heating. However, if the temperature is too high, the oxide superconductor will deteriorate, so an appropriate temperature should be selected. Furthermore, if water vapor is added to the atmosphere at this time, there is a further significant effect of promoting the reaction.

In addition, the second metal film 5 contains, for example, AI or Zn.
It is preferable that metal atoms having a smaller atomic radius than lead, such as lead, be added in advance in an amount of about 15% by weight or less. This is because the presence of metal atoms such as AI with a small atomic radius prevents the grain size of the insulating material 6 from growing large, and many finely divided insulating materials 6 are formed.
As a result, the crystal grain size of the insulating material 6 obtained becomes fine and a dense film is obtained, and the region between the oxide superconductor thin film 2 and the insulating material 6 becomes clearer, forming a fine superconducting region pattern. It becomes possible to do so.

The addition of metal atoms with a small atomic radius is particularly effective when the reaction is accelerated by applying heat or adding water vapor during the reaction.

Thereafter, the second metal film 5 made of lead remaining on the first metal film 4 mainly made of noble metal is removed using hydrochloric acid diluted to about 10%. As a result, the portion of the Ln-M-Cu-0 based oxide superconductor thin film 2 covered by the first metal film 4 maintains its initial film quality as a superconductor region 7, and the second layer made of lead surrounding it maintains its initial film quality. The part that has reacted with the metal film 5 becomes a semi-transparent insulating material 6 and forms a field region 8.
A superconductor device is obtained in which the periphery of the target superconductor region 7 is insulated and elements are isolated (FIG. 1-f).

According to the steps of this example described above! 1irT1
Formation of a patterned first metal film 4 made of silver on a Y-Ba-Cu-0 based oxide superconductor thin film 2 formed on the surface of an insulating substrate 1 made of a 0i substrate by a magnetron bag method; Formation of a second metal film 5 containing lead as a main component on the first metal film 4, Y-Ba-Cu- of the portion not covered with this second metal film 5 and the first metal film 4
When the specific resistance of the obtained insulating material 6 was measured by sequentially reacting with the 0-based oxide superconductor thin film 2, it was found to be 106Ω.8
It was 111 or more and had good insulation properties. In addition, the portion of the Y-Ba-Cu-0 based oxide superconductor thin film 2 that was previously covered with the first metal film 4 remains unchanged, and the initial film quality remains unchanged.
In other words, it was confirmed that the superconducting properties were maintained and that the elements were completely isolated from each other.

Furthermore, according to the results of analyzing the components of this insulating material 6 using Auger analysis, in addition to yttrium, barium, copper, and oxygen, lead was clearly detected, indicating that the insulating material was formed as a compound or mixture of these. was confirmed.

According to the embodiment described above, the oxide superconductor thin film 2 on the insulating substrate 1 can be formed into a desired pattern shape without exposing its side surfaces, and can be electrically insulated from each other to ensure reliability. It is possible to perform isolation between elements. Therefore, the obtained superconductor device can selectively obtain only the superconducting properties due to the plane direction of the oxide superconductor film.

Further, according to the manufacturing process of the above embodiment, since the first metal film mainly made of noble metal is formed by patterning in advance on the portion to be left as a superconducting region, it is sufficient to cope with the miniaturization of the superconducting region. becomes possible. That is, since the first metal film that becomes the superconducting region is formed by patterning using the lift-off method, the area where the mask material that becomes the field region is formed becomes relatively large, and conversely, the exposed portion becomes a minute area. This is because it becomes possible to accurately remove the mask material.

In the above embodiments, silver was used as the material separating the oxide superconductor and lead, but the reaction can also be effectively blocked using other noble metals such as gold or platinum. In addition, when depositing the first metal film containing noble metal as the main component,
If the etching rate between the first metal film and the Ln-M-Cu-0-based oxide superconductor film can be accurately controlled, a method of forming a pattern by ion milling or the like using a photoresist pattern may be used. You can also use

Further, in the superconductor device obtained in the above example, the superconducting region is covered with a first metal film made of silver or the like. And these precious metals and Ln-M-C
A good ohmic contact with extremely low resistance is formed between the u-0 series oxide superconductor and the current flowing between the two layers flows through the superconductor film with lower resistance, so normal superconducting electrons When used as a device or wiring,
Such a two-layer film structure can be used as is.

In addition, Ln-M-Cu-0-based oxide superconductors react with moisture in the air and form a surface deterioration layer, but the first metal film mainly made of noble metal that coats the surface Since it also functions as a protective film, use of such a two-layer film structure provides strong device stability. In particular, when silver is used as the surface layer, Y-Ba-Cu
A very long superconducting proximity effect has been observed from oxide superconductor films such as -0 series, and this is advantageous because the entire two-layer film can be used as a superconducting film. Note that if it is necessary to expose the oxide superconductor film for special reasons, the first metal film is removed from a part or the entire surface of the oxide superconductor film using ion milling or the like as described above. It is possible to remove the oxide superconductor film and expose the oxide superconductor film.

Next, another embodiment of the present invention will be described with reference to FIG.

First, a first metal film 4 mainly made of a noble metal is patterned on the Ln-M-Cu-0-based oxide superconductor thin film 2 in a portion to be left as a superconducting region, as in the above-mentioned embodiment. A second metal Jli5 containing lead as a main component is formed only within a certain range so as to surround the first metal film 4, including on the first metal film 4 (FIG. 2-a).

Next, as in the above embodiment, the second metal film 5 containing lead as a main component is reacted with the Ln-M-Cu-0 based oxide superconductor thin film 2 that is in direct contact with the insulating material. form 6 (
Figure 2-b).

Thereafter, the second metal film 5 mainly composed of lead remaining on the first metal film 4 mainly composed of noble metal is removed in the same manner. As a result, the I, nM-Cu-0 based oxide superconductor thin film 2 in the portion covered by the first metal film 4 maintains its initial film quality as a superconductor region 12. Furthermore, although there is a remaining portion 13 of the oxide superconductor thin film 2 in the field region 12 surrounded by the insulating material 6, the superconducting region 11 is well isolated between elements by the insulating material 6. Therefore, a superconductor device with the desired separation between elements can be obtained in the same way as in the previous embodiment (
Figure 2-C).

According to this embodiment, by limiting the formation range of the second metal film containing lead as a main component to a range where sufficient isolation can be achieved between elements, the oxide covered by the metal film containing lead as a main component can be removed. Because the superconductor film and the exposed oxide superconductor film coexist side by side, moisture in the air involved in the reaction reaches the interface between the oxide superconductor film and the lead-based film. This makes it easier to form the insulating material, making it possible to increase the formation speed of the insulating material. Note that in order to control the formation range of the second metal film containing lead as a main component, for example, a lift-off method may be used.

In addition, in the above example, Y-Ba-Cu is used as the superconducting material.
Although the description has been made using a Y-0 based oxide superconductor film, the present invention is not limited thereto;
It has been confirmed that materials in which yttrium, the main component of the a-Cu-0-based oxide superconductor film, is replaced with other rare earth elements, such as lanthanum, can be insulated by a similar reaction, and this study The invention is effective for various Ln-M-Cu-0-based oxide superconductors.

[Effects of the Invention] As explained above, according to the method for manufacturing a superconductor device of the present invention, the side surfaces of the Ln-M-Cu-〇-based oxide superconductor film formed on an insulating substrate are exposed. It is possible to form a pattern with the desired shape that is insulated and separated without causing any damage.
Furthermore, a finely patterned superconducting region can be formed with good reproducibility. Therefore, it is possible to reliably obtain a superconducting electronic device with constant superconducting properties and a high degree of integration.

[Brief explanation of drawings]

FIGS. 1(a) to (f) are cross-sectional views showing the manufacturing process of a superconductor device according to one embodiment of the present invention, and FIGS. 2(a) to (c) are superconductors according to another embodiment of the present invention. FIG. 3 is a cross-sectional view showing the manufacturing process of the device. 1...Insulating substrate, 2...Ln-M-C
u-0 based oxide superconductor film, 3... Photoresist film, 4... First metal film containing noble metal as main component, 5... Mainly containing lead. a second metal film as a component;
6... Insulating material, 7.11... Superconducting region, 8.12... Field region. Applicant: Toshiba Corporation, Agent: Patent Attorney Suyama Sa - J

Claims (1)

[Claims] (1) Ln-M-Cu-O based oxide superconductor on an insulating substrate (Ln is at least one element selected from rare earth elements, M is at least one element selected from alkaline earth elements)
Indicates the species element. ) film forming process and this Ln-M
- Forming a first metal film containing a noble metal as a main component on the Cu-O based oxide superconductor film according to the shape of a desired superconducting region; a step of forming a second metal film containing lead as a main component on the Ln-H-Cu-O-based oxide superconductor film continuously on the film; and a second metal film containing lead as a main component. film and the L below this second metal film.
A method for manufacturing a superconductor device, comprising the step of reacting with an n-M-Cu-O based oxide superconductor film to form an insulating material.