JPH0829939B2 - Method for producing high temperature oxide superconductor thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for producing a high-temperature oxide superconductor thin film that can be used, for example, in sensor elements, IC wiring, electronic devices, and the like.

<Prior art and its problems> Oxide high-temperature superconductors are so-called ceramics,
It is generally manufactured by mixing powder raw materials and sintering. In addition, the sputtering method is often used for the purpose of electronics application in the attempt of thinning the superconductor, and recently, the EB vapor deposition method and the MBE method are being tried. However, the drawback of these methods is that the substrate temperature is about 800
In addition to the need to keep at a high temperature of ℃, after once forming the film, the film is heated again in oxygen or air at a high temperature of 8 to 900 ℃ so that oxygen can be sufficiently incorporated into the film. It exhibits superconductivity for the first time, and the substrate temperature at the time of film formation is high, and the heat treatment for higher temperature oxidation required after film formation is performed on electronic materials such as semiconductors and circuits formed on it. There is a drawback that it has a very bad effect on the device. It is no exaggeration to say that these drawbacks are one of the causes that hinder the application of the oxide superconductor to electronics. In the sputtering method, Ar gas, which is the sputter gas, is easily incorporated into the film as impurities, which causes deterioration of the film quality.In addition, the composition of the target material and the composition of the formed film are different, and it is When it is composed of elements and its composition ratio sensitively affects superconductivity, it is never easy to set the target composition and the film forming conditions, and after repeating a great deal of trial and error. Therefore, a complicated and difficult technique is required to produce a film with excellent characteristics for the first time.

The above sputtering method, EB vapor deposition method, and MBE method,
Although it is a vapor deposition method called physical vapor deposition method,
There is a so-called chemical vapor deposition method. Among chemical vapor deposition methods, as a thin film deposition method for electronic devices,
The chemical vapor deposition method (CVD method) is typical. In addition, CVD
One of the methods is plasma metalorganic vapor phase epitaxy (plasma
There is something called the MOCVD method). Plasma MOCVD method
A metal-organic compound is used as a vapor deposition material, and the gas of this metal-organic compound, which is the vapor deposition material, is plasma-excited to perform film formation.Compared to other CVD methods, the film formation temperature is lowered and the growth rate is increased. Is relatively easy to control. However, since the plasma MOCVD method uses a vapor deposition material as an organometallic compound and uses a gas such as argon as a carrier gas, carbon, argon, etc. are mixed as impurities in the film, which deteriorates the film quality of the thin film. In addition, the film forming process has not been sufficiently clarified, and the film quality varies depending on the film forming apparatus, and it is difficult to stably manufacture a thin film having high reliability. Besides this,
There are also drawbacks such as slow film formation speed compared to physical vapor deposition,
The plasma MOCVD method has many problems as a film forming method for producing a highly reliable thin film having stable characteristics.

The present invention was made in view of the above points, and an object thereof is to provide a novel method for producing a high-temperature oxide superconductor thin film, which eliminates the above-mentioned conventional problems.

<Means for Solving Problems> In order to achieve the above-mentioned object, the method for producing a high temperature oxide superconductor thin film according to the present invention uses oxygen plasma generated in a vacuum chamber or oxygen plasma. A method of forming a high temperature oxide superconductor thin film by passing through and vaporizing constituent element ions other than oxygen of the high temperature oxide superconductor by a physical vapor deposition method, wherein the first evaporation material is yttrium or the like. Using rare earth element in the state of metal or its fluoride,
As a second vapor deposition material, an alkaline earth element such as barium is used in a metal or its fluoride state, and as a third vapor deposition material, copper is used in a metal state, and a positive potential is applied to the substrate, It is formed by the ternary component simultaneous vapor deposition method.

That is, according to the present invention, in order to solve the above-mentioned conventional problems, in the physical vapor deposition method, firstly, the substrate temperature is lowered, secondly, oxidation treatment at a high temperature is unnecessary, and thirdly,
The present invention proposes a manufacturing method for forming a high-quality uniform high-temperature oxide superconductor thin film after improving the three points that the composition of the film can be changed relatively easily. In the method of the invention, a small amount of oxygen is introduced into a high-vacuum chamber and discharged by applying a high-frequency electric field to activate oxygen gas in a plasma state to activate the remaining components in the plasma state. At the same time, they are evaporated into molecules by separate heating means, and a metal of lanthanide element such as yttrium or lanthanum or its fluoride and a metal of alkaline earth element such as barium or strontium or its fluoride (eg BaF ₂ ) By fully reacting each constituent element of copper with oxygen, a good quality superconductor thin film can be formed at a relatively low substrate temperature of about 600 ° C. In addition to the above, scandium can be used as the lanthanide element, and not only the metal of the lanthanide element but also its fluoride can be used.

At this time, the content of oxygen in the film can be controlled by changing the oxygen gas pressure, but it is relatively easy to do by adjusting the evaporation amount of other elements, especially copper element, and the evaporation amounts of yttrium and barium. It In addition, by activating oxygen in a plasma state, not only the high temperature oxidation treatment after film formation is unnecessary, but also the film formation rate is greatly improved as compared with the conventional physical vapor deposition method.

The method for producing a high-temperature oxide superconductor thin film according to the present invention is a method in which a constituent ion of an oxide superconductor is vaporized individually in oxygen plasma activated in a vacuum reaction chamber, so that a substrate on a relatively low temperature is formed. An oxide superconductor thin film is formed on.
Further, in this case, the ionized material elements become active, facilitating the bonding of the respective constituent ions and at the same time sufficiently oxidizing them to form an oxide superconductor at a relatively low temperature.

<Example> Hereinafter, an example of the present invention will be described in detail.

FIG. 1 is a schematic diagram showing a configuration example of a manufacturing apparatus used for carrying out the present invention. In the figure, 1 is a vacuum chamber, 2 is a substrate, 3a and 2b are electron beam (EB) heating devices,
Reference numeral 4 is a tungsten (W) heater, 5 is a high frequency antenna coil, 6 is oxygen plasma, 7 is a high frequency power supply, and 8 is a bias power supply.

First, a high vacuum chamber 1 equipped with two electron beam (EB) heating devices 3a and 3b, one tungsten (W) heater 4 and a high frequency plasma generating coiled antenna 5 shown in FIG. After exhausting up to 10 ^-8 Torr level and finally using a cryopump, oxygen gas was introduced up to 2 × 10 ^-4 Torr, and the antenna coil 5 equipped in the vacuum chamber 1 was supplied with a high frequency of 13.56 MHz at 180 W. The oxygen gas was supplied and discharged to be excited into a plasma state. Separate electron beam (EB) heating devices 3a and 3b for copper and yttrium (Y) metal, respectively
In heating, as the barium source was vaporized in heat independently BaF ₂ tungsten heater 4 molecular. Substrate 2 was a 1 cm square substrate of yttrium-stabilized zirconia with a thickness of about 1 mm, and was kept at a temperature of 600 ° C. Electron beam (EB)
The emission current for heating was about 150 mA for copper and about 70 mA for yttrium (Y). The tungsten heater 4 was a small boat, and the temperature was not accurately measured by energizing 75 A, but it was heated to an incandescent state and BaF ₂ could be evaporated. The substrate 2 and the substrate support are 150V by the bias power supply 8.
The positive potential of is applied.

When the film is formed under the above conditions, the resistance is reduced to zero.
Since the film shown at a temperature of 77K or higher was obtained, it is considered to be relatively close to the optimum condition. It was judged from the spread of plasma emission that the oxygen plasma was generated over a wide range in the tank 1 during the film formation, and the substrate 2 was exposed to one end of the plasma. The substrate support was placed electrically grounded. The film forming rate at this time was such that a thin film of about 8000Å was formed in 2 hours, so that a film forming rate of 0.1 μm per hour was obtained. When it was taken out from the vacuum deposition tank 1 and immersed in liquid nitrogen, and the resistance was measured by the four-terminal method, it showed a low resistance sufficient to recognize that it had a superconductivity of μΩ or less. It is thought that The resistance of this thin film at room temperature was about 10 mΩ. It should be said that the formation of the superconducting thin film using the physical vapor deposition method without the low temperature substrate temperature and the high temperature oxidation treatment is epoch-making.

<Effect of the Invention> The effect of the present invention is clear as compared with the prior art.

That is, the method of the present invention is an improvement of the physical vapor deposition method that can obtain a good quality thin film, and has the first effect that the substrate temperature can be lowered as compared with the conventional physical vapor deposition method. It is a thing.

That is, in the conventional physical vapor deposition method, the sputtering method and the EB beam vapor deposition method were mainly used as the oxide superconductor film forming method, but in both cases, the substrate temperature was both.
It is a high temperature of 800 to 900 ° C., and the condition that the substrate temperature must be high causes a deterioration of elements on the substrate for the semiconductor substrate, so it must be called a fatal drawback. However, in the present invention, a film can be formed at a low substrate temperature of about 600 ° C., which is an advantage that a superconducting film can be formed on a semiconductor substrate or an element. The reason for this is that the raw material ions of copper, alkaline earth metal, lanthanide, etc. are excited and activated by the oxygen plasma excited by the high frequency, and the formed metal ions and oxygen ions are respectively excited energy. In the conventional physical vapor deposition method, the excitation energy and the energy of the kinetic of the collision cause a large amount of surface diffusion of ions locally on the substrate and promote crystal growth. It is considered that it acts as an alternative to the heating of the substrate at a high temperature to enable film formation at a relatively low substrate temperature.

Secondly, the excellent effect of the present invention, which is secondly recognized, is that the oxidation treatment by the film-forming heating, which is all necessary in the conventional physical vapor deposition method described above, is not necessary in the present invention. In general, oxidation treatment by heat treatment is not preferable because it does not have a good effect on the substrate and particularly on the semiconductor element. The effect of eliminating this heat treatment is not only to save labor but also to enable the use of semiconductors as substrates.

Furthermore, according to the present invention, since oxygen plasma is used by using only the elements that form the thin film to be formed as the vapor deposition material, impurities such as carbon and argon are mixed into the thin film, and the film formation speed is slow and the characteristics are stable. As compared with chemical vapor deposition methods such as plasma MOCVD method, which has various problems as a film forming method for producing a highly reliable thin film with high reliability, an extremely high-purity high-temperature oxide superconductor thin film is used. It becomes possible to manufacture.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an apparatus used in one embodiment of the present invention. 1 ... Vacuum chamber, 2 ... Substrate, 3a, 3b ... Electron beam (E
B) Heating device, 4 ... Tungsten heater, 5 ... High frequency antenna coil, 6 ... Oxygen plasma, 7 ... High frequency power source.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 39/24 ZAA B // C30B 29/22 ZAA Z 9261-4G

Claims (1)

[Claims] 1. A substrate on which a constituent element ion other than oxygen of a high-temperature oxide superconductor is vapor-deposited by physical vapor deposition in oxygen plasma generated in a vacuum chamber or through oxygen plasma. And a rare earth element such as yttrium in the form of a metal or its fluoride as a first vapor deposition material, and an alkali such as barium as a second vapor deposition material. The earth metal element is used in the state of metal or its fluoride, copper is used as the third vapor deposition material in the state of metal, and a high temperature oxide is formed by the ternary component co-evaporation method with a positive potential applied to the substrate. A method for producing a high temperature oxide superconductor thin film, which comprises forming a superconductor thin film.